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Hormone Health Guide

Our hormones affect everything from how fast our heart beats to how easily we get to sleep at night. Understanding them and knowing what is normal for our stage of life helps us learn what to look out for when things go wrong. 

Dr Sam Rodgers - Chief Medical Officer

Reviewed by Dr Sam Rodgers

5th December 2019


What are hormones and how do they work?

Chapter 1

What are hormones and how do they work?

The hypothalamus

Chapter 2

The hypothalamus

The pituitary gland

Chapter 3

The pituitary gland

The adrenals

Chapter 4

The adrenals

The gonads

Chapter 5

The gonads

The thyroid and the parathyroid glands.

Chapter 6

The thyroid and the parathyroid glands.

The pancreas, the pineal and the thymus

Chapter 7

The pancreas, the pineal and the thymus

What are hormones and how do they work?

Chapter 1

What are hormones and how do they work?

Find out about the system that governs your hormone production and learn about what hormones are and what they do.

Hormones are chemical messengers which move through the body co-ordinating a multitude of bodily processes. Each hormone targets a different part of the body and has a very specific job to do. Target cells are equipped with receptors that the hormone binds to; this creates a biological reaction which has an effect on the body. A hormone cannot bind to a cell unless it has receptors for it, but cells can have receptors for many different hormones.

Your hormones are responsible for many body functions, including growth, metabolism, reproduction and homeostasis (maintaining the body’s internal balance).

What are hormones made from?

There are 3 types of hormone – protein (or peptide) based, lipid-based and amino acid-based.

  • Protein-based hormones. These include follicle stimulating hormone (FSH) and the “feel good” hormone oxytocin.
  • Lipid-based hormones. These are the steroid hormones which are formed from cholesterol and structurally are very similar. They include oestradiol and testosterone.
  • Amino acid-based hormones. These are simple molecules which are not fat-soluble – they include the thyroid hormones thyroxine and triiodothyronine and melatonin.

The endocrine glands

The endocrine glands are responsible for releasing hormones into the bloodstream so that they can travel to the target cells and create a biological response. The endocrine system is a tightly regulated system that manages the release of hormones and their effects on the body. It operates in a signalling “feedback-loop” so that the release of hormones can be increased or slowed down to maintain their effects at just the right level.

There are 10 main glands in the endocrine system – the hypothalamus, the pituitary, the adrenals, the thyroid, the ovaries, the testes, the pancreas, the parathyroid, the pineal and the thymus. Each has a very specific role to play in the body - we’ll take a look at each of them and what they do in the following chapters.

The hypothalamus

Chapter 2

The hypothalamus

Ever wondered what keeps your body from over-heating or why you get thirsty? This little area set deep in your brain has the answers.

Buried deep in the brain, the hypothalamus is responsible for homeostasis (keeping the body in balance) and hormones. Read on to find out more about its role in the body and about the hormones it produces and controls.

What is the hypothalamus and what does it do?

The hypothalamus is a small area of the brain which is located between the pituitary gland and the thalamus. Its main role is to keep the body in healthy balance (homeostasis) by releasing hormones to stimulate or inhibit other hormones which govern bodily processes. The hypothalamus is part of the feedback loop which tells the body whether to produce more or less of a certain hormone to keep the body in balance.

The hypothalamus is responsible for the processes which regulate:

  • Heart rate and blood pressure
  • Appetite and thirst
  • Sex drive
  • Childbirth
  • Body temperature
  • Sleep cycle
  • Emotional response

What hormones are produced in the hypothalamus?

There are two types of hormones produced by the hypothalamus – those that travel to the pituitary where they are released directly into the bloodstream (oxytocin and anti-diuretic hormone), and those that travel to the pituitary where they control the production and release of further hormones which stimulate other parts of the endocrine system.

  • Anti-diuretic hormone (ADH) - ADH (or vasopressin) controls the reabsorption of water into the blood from the kidneys.
  • Corticotropin-releasing hormone (CRH) - CRH controls the release of ACTH (see next chapter) by the pituitary gland to regulate the production of adrenal hormones.
  • Gonadotropin-releasing hormone (GRH) - GRH stimulates the release of luteinising hormone (LH) and follicle stimulating hormone (FSH) by the pituitary gland. Growth hormone-releasing hormone (GHRH)/Growth hormone-inhibiting hormone (GHIH) GHRH and GHIH stimulate the release or inhibition of growth hormone by the pituitary gland. Growth hormone controls the growth and repair of cells throughout our lives.
  • Oxytocin - Oxytocin is the hormone that stimulates the womb to contract during labour and the release of milk for breastfeeding.
  • Prolactin-releasing hormone (PRH)/Prolactin inhibiting hormone (PIH) - PRH and PIH control the release or inhibition of prolactin by the pituitary gland. Prolactin stimulates the production of breast milk.
  • Thyrotroptin-releasing hormone (TRH) - TRH stimulates the release of thyroid stimulating hormone (TSH) by the pituitary gland. TSH controls the production of thyroid hormones which regulate metabolism.

What can go wrong with the hypothalamus gland?

Problems with the hypothalamus are often caused by trauma to the brain either through a head injury or surgery, or by tumours which are in or close to the hypothalamus and affect its functioning. Other causes of hypothalamus disorders can be genetic or can be caused by malnutrition (including eating disorders such as anorexia), or infection and inflammation of the brain.

What are the symptoms of hypothalamus dysfunction?

The hypothalamus has a wide role in the body, therefore a disorder of the hypothalamus can have many consequences which can make it difficult to diagnose. The hypothalamus is part of a communication system with the pituitary gland which in turn controls hormone production in other hormone glands. Hypothalamus dysfunction can be difficult to distinguish from pituitary dysfunction, and both can cause the same symptoms as disorders of the other endocrine glands e.g. thyroid or adrenal disorders.

Symptoms of hypothalamus dysfunction can include:

  • Failure to grow and thrive
  • Delayed puberty
  • Changes in appetite
  • Weight gain and fatigue
  • Unexplained weight loss
  • Fertility problems
  • Problems regulating body temperature

Diagnosis and treatment of hypothalamic disorders

Diagnosis of a hypothalamic disorder made after a combination of clinical examination including eye tests and brain imaging to detect any lesions, as well as hormone blood tests to measure levels of circulating hormones. Low levels of hormones can be treated with hormone replacement therapy while surgery may be necessary to remove any physical pressure on the gland.

The pituitary gland

Chapter 3

The pituitary gland

How are hormones turned on and off? Learn how the pituitary gland is the conductor of the endocrine orchestra and what happens when your hormones get our of synch. 

It may be small, but the pituitary gland is the “master gland” of the endocrine system, signalling endocrine glands all over the body to increase or decrease their hormone production. Learn more about how the pituitary gland controls hormone production and what can happen if things go wrong.

What is the pituitary gland and what does it do?

The pituitary gland is a small pea-sized gland located in the base of the brain. It is often referred to as the “master gland” as it controls the production of hormones in most of the endocrine glands in the body. The pituitary gland has two lobes which are connected to the hypothalamus gland by a stalk.

The anterior lobe of the pituitary gland is responsible for producing the hormones which signal other hormone glands to increase or decrease hormone production. These hormones include:

  • Adrenocorticotrophic hormone (ACTH) - ACTH stimulates the adrenal glands to produce cortisol, a steroid hormone which influences many different processes around the body including metabolism and immune response. ACTH levels are highest in the morning and gradually decline during the day.
  • Follicle stimulating hormone (FSH) - FSH is an important reproductive hormone. In women, it stimulates the growth of ovarian follicles (eggs) in the ovaries and in men, the testes to produce sperm. In women, FSH levels rise as the number of viable eggs declines with age. Elevated FSH is a marker for menopause in women.
  • Growth hormone (GH) - Growth hormone is produced in the anterior gland of the pituitary where it is released into the bloodstream. It acts on many cells in the body, working to stimulate growth and cell reproduction and repair. Growth hormone, also known as human growth hormone (HGH) rises in childhood and declines from middle age.

  • Luteinising hormone (LH) - LH is a gonadotrophic hormone, essential for the reproductive health of men and women. In men, it stimulates the Leydig cells in the testes to produce testosterone. In women, it plays a role in the menstrual cycle and preparing the body for pregnancy – stimulating the ovaries to produce oestradiol in the first half of the cycle and the corpus luteum to produce progesterone in the second half. A surge in LH triggers the ovary to release an egg (ovulation) mid-way through the menstrual cycle.
  • Melanocyte stimulating hormones (MSH) - MSH is the name for a group of hormones which have a range of functions, from stimulating the production of melanin in the skin (pigmentation) to controlling inflammation and appetite. It is produced in the pituitary gland as well as the skin and hypothalamus gland.
  • Prolactin (PRL) - Prolactin is the hormone that is responsible for lactation, the production of breast milk. It also has a role in men and women for sexual satisfaction, behaviour and the regulation of immune function.
  • Thyroid stimulating hormone (TSH) - TSH stimulates the thyroid gland to produce thyroid hormones which govern the body’s metabolic rate, influencing virtually every cell of the body.

The posterior lobe of the pituitary gland does not produce hormones but acts as storage and release for oxytocin and anti-diuretic hormone, which are produced in the hypothalamus. As such, it acts as an extension of the hypothalamus gland.

What can go wrong with the pituitary gland?

As with the hypothalamus, injuries or trauma to the head can cause problems in pituitary function as can tumours in the brain which put pressure on the pituitary gland. By far the most common cause of a pituitary disorder is a tumour of the pituitary gland itself. The vast majority of pituitary tumours are benign (non-cancerous) and some do not have any effect on hormone production (non-functioning tumours). However, some pituitary tumours can cause the over-production of one or more pituitary hormones, while others can cause the suppression of hormone production (hypopituitarism, or underactive pituitary gland).

Disorders of the pituitary gland include:

  • Cushing’s disease (too much cortisol).
  • Prolactinoma (too much prolactin caused by a prolactin-producing tumour)
  • Acromegaly (too much growth hormone)
  • Growth hormone deficiency (growth hormone suppression)
  • Diabetes insipidus (suppression of anti-diuretic hormone affecting the kidney’s ability to retain water)

What are the effects of hypopituitarism (an underactive pituitary gland)?

Problems with your pituitary can affect its ability to produce one or more hormones which can have wide ranging implications for your health, depending on which hormones are affected:

  • Follicle stimulating hormone (FSH) – egg and sperm production
  • Luteinising hormone (LH) – menstruation, testosterone production and fertility
  • Growth hormone (GH) – growth in children and a range of issues in adulthood
  • Thyroid stimulating hormone (TSH) – maintenance of normal metabolism
  • Adrenocorticotrophic hormone (ACTH) – adrenal function
  • Prolactin (PRL) – production of breast milk

What are the symptoms of a pituitary gland disorder?

As the pituitary gland plays such a central role in orchestrating the production and release of many hormones throughout the body and can affect a single or multiple hormone system, the symptoms of a pituitary disorder can be wide-ranging. They can also be confused with other conditions and many pituitary disorders go undiagnosed. Symptoms will vary according to whether the pituitary disorder is causing over or under-production of the affected hormone. Symptoms will depend on which endocrine gland is ultimately affected.

Symptoms of a pituitary disorder can include:

  • Loss of libido
  • Inability to gain muscle
  • Infertility
  • Irregular periods
  • Weight gain
  • Weight loss
  • Sensitivity to heat or cold
  • Hirsutism (hairiness)
  • Excessive thirst and frequent urination
  • Mood swings and depression
  • Constipation
  • Difficulties sleeping
  • Milky discharge from nipples (in both men and women)
  • Muscle and joint aches
  • Fatigue

This list is by no means exhaustive and you should make a note of all symptoms which apply to you so that your doctor can confirm or rule out a pituitary disorder.

How is a pituitary disorder diagnosed and treated?

A pituitary disorder is diagnosed through a combination of a physical examination (including eye examination and brain imaging to detect tumours) and symptoms as well as hormone blood tests which can detect unusual levels of hormones in the blood. A pituitary disorder is often picked up as an incidental finding on a test even if you are not experiencing symptoms.

Many pituitary tumours do not require treatment. However, if the tumour is causing over-production of certain hormones or is putting pressure on the optic nerve, surgery or radiation therapy may be required to remove it.

Hormone replacement therapy or hormone blocking treatments can normalise the under-production or over-production of hormones.

The adrenals

Chapter 4

The adrenals

Rapid heartbeat, sweaty palms, ready to run? Learn about the glands that control your flight or fight response and what happens to your body when you experience stress.

Learn about the hormones which govern your stress response and find out why your doctor is unlikely to diagnose you with adrenal fatigue.

What are the adrenal glands and what do they do?

The adrenal glands are two triangular-shaped glands that sit on top of the kidneys. They are best known for producing the hormones which govern our stress response, but they also have an important role to play in metabolism, the immune function and regulation of blood pressure.

The adrenal glands are made up of two parts; the cortex and the medulla, and each is responsible for producing different hormones. The adrenal cortex is the outer part of the adrenal glands and is responsible for producing hormones which are vital for life – the glucocorticoids, mineralocorticoids and adrenal androgens. The adrenal medulla is the inner part of the adrenal glands and is responsible for producing catecholamines, the hormones that are released in our “fight or flight” response.

What hormones are produced in the adrenal glands?

Adrenal Cortex

Cortisol (a glucocorticoid) is the best-known hormone of the adrenal cortex. It has a role in metabolism, signalling the body when to convert fat, proteins and carbohydrates into glucose for energy. It also has an important role to play in the body’s stress response, releasing glucose to provide an energy boost in an emergency, as well as shutting down non-essential bodily functions (digestion, immune function, reproduction) to preserve energy.

Aldosterone (a mineralocorticoid) helps the body regulate blood pressure and maintain the level of electrolytes (sodium and potassium) in the blood.

Androgens (DHEA and testosterone) are also produced by the adrenal cortex. These are precursor hormones which are converted to male hormones in the testes and to female hormones in the ovaries. Testosterone and oestradiol are also produced in much larger amounts directly in the testes and ovaries.

Adrenal Medulla

Adrenaline (epinephrine) is a neurotransmitter and hormone which is released into the bloodstream when a person is under stress or in danger with the aim of making them physically more able to deal with the threat, i.e. the fight or flight response. Adrenaline increases blood sugar for energy, causes the heart muscle to contract faster and harder to get more blood to the muscles and the brain, and relaxes the airways to get more oxygen to the lungs. Once the perceived threat has gone, adrenaline levels go back to normal.

Noradrenaline (norepinephrine) is very similar to adrenaline, but also acts to constrict blood vessels to increase blood pressure in times of stress.

What can go wrong with the adrenal glands?

Adrenal disorders are usually caused by the over or under-production of adrenal hormones which can be caused by adrenal or pituitary problems. Adrenal disorders include Cushing’s disease and Addison’s disease.

Cushing’s disease.

Cushing’s disease or Cushing’s syndrome is caused when the body produces too much cortisol. This can be caused by a pituitary disorder (often a tumour) which causes too much ACTH to be produced which overstimulates the adrenal glands to produce cortisol, or by a tumour on the adrenal glands themselves. Cushing’s can also be caused by taking steroid medication, or by an ACTH-producing tumour elsewhere in the body. Cushing’s is rare, and most often affects women between the ages of 30 and 40.

What are the symptoms of Cushing’s disease?

Cushing’s disease causes a number of symptoms including:

  • A fatty “hump” on the back of the neck and shoulders
  • Weight gain around the torso (but not arms and legs)
  • A round, red puffy face
  • Purple stretch marks
  • Acne
  • High blood sugar/diabetes
  • Irregular periods
  • Loss of libido
  • Infertility
  • Excessive hair growth on the face and body (women)
  • Mood swings and depression
  • Low bone density

How is Cushing’s disease diagnosed?

Cushing’s disease can be difficult to diagnose, especially as some of the symptoms are common with other conditions. Typically, diagnosis will be made with a series of tests to measure cortisol production over the course of a day (urine, saliva or blood tests), a physical examination and scans to detect whether there is a pituitary or adrenal tumour. Sometimes a cortisol mimicking drug will be given, which in someone without Cushing’s would cause a reduction in cortisol but has no effect on people with Cushing’s disease.

How is Cushing’s disease treated?

Treatment will depend on what is causing the production of excessive cortisol. This can mean surgery to remove a pituitary or adrenal tumour, or even removal of the adrenal glands themselves, or the gradual reduction of steroid treatment if this has caused the problem. Medication can also be prescribed which suppresses cortisol production, although this is normally a short-term solution.

Addison’s disease.

Addison’s disease is also known as adrenal insufficiency and occurs when your adrenal glands don’t produce enough hormones. In primary adrenal insufficiency, the problem is caused by damage to the adrenal cortex, usually because of an autoimmune disease where the body starts attacking its own tissues.

Primary adrenal insufficiency affects the production of both cortisol and aldosterone and causes wide ranging symptoms including weight loss, areas of dark skin and low blood pressure. Secondary adrenal insufficiency is normally caused by a pituitary problem (usually a tumour) which results in a reduced production of ACTH which then fails to stimulate the adrenal glands to produce cortisol and androgens (aldosterone is unaffected).

Taking steroid medication (e.g. for asthma or rheumatoid arthritis) can also affect adrenal function. The pituitary gland which normally regulates the output of adrenal hormones senses that there are normal levels of steroid hormones in the blood (due to the medication) and stops sending signals to the adrenal glands to make more. This doesn’t usually cause problems until a time of severe stress (when insufficient hormones are released to manage the stress response), or if steroid medication is stopped too quickly.

Addison’s disease can develop slowly and in its early stages can be mistaken for other conditions. However, when more advanced, or if symptoms deteriorate sharply (adrenal crisis), Addison’s disease can be life-threatening.

What are the symptoms of Addison’s disease?

  • Unintended weight loss
  • Loss of appetite
  • Hyperpigmentation (darkening of the skin)
  • Low blood sugar
  • Low blood pressure
  • Fatigue
  • Salt cravings
  • Increased thirst
  • Irritability and depression
  • Muscle weakness and aches and pains
  • Nausea and gastrointestinal problems
  • Irregular menstrual periods and loss of pubic and underarm hair

How is Addison’s disease diagnosed?

Addison’s disease is normally diagnosed through a combination of a physical examination, including a blood pressure test to check for low blood pressure, and tests (blood, urine or saliva) to measure levels of adrenal and pituitary hormones. Tests for cortisol, ACTH, aldosterone, DHEA, may all be used to make a diagnosis while tests for sodium, potassium and glucose can help to distinguish between primary and secondary adrenal insufficiency. For confirmation, a synacthen stimulation test is performed. Synacthen is a synthetic form of ACTH and should stimulate the adrenal glands to make cortisol. If, after an injection of synacthen adrenal hormones remain low, then adrenal insufficiency is confirmed. An adrenal antibody test can confirm whether an autoimmune disorder is causing the adrenal glands to fail.

How is Addison’s disease treated?

Addison’s disease or primary adrenal insufficiency is normally treated by replacing the adrenal hormones that are missing. Hydrocortisone is a synthetic hormone which is used to replace the glucocorticoid, cortisol. If aldosterone is also affected then a replacement mineralocorticoid (fludrocortisone) is prescribed alongside a recommendation to increase salt in the diet if needed.

Adrenal Fatigue – Q&A

What is adrenal fatigue?

As we’ve learned, the adrenal glands are two small glands that sit on top of your kidneys and are responsible for the production of hormones that control your body’s response to stress, in particular cortisol. The theory behind adrenal fatigue is that if you suffer from an acutely stressful event, or suffer from prolonged, chronic stress, then your adrenal glands can become overloaded and ineffective, failing to produce the right amount of cortisol for the demands of the body at the right time of day.

Normally, cortisol levels are highest in the morning on waking, and decline naturally through the day until their lowest level, just before bed. This means that we wake with energy and vitality to take on the day ahead, and fall asleep in an easy and relaxed state at bed-time. If the cortisol cycle is broken, then the theory goes that this can lead to you feeling exhausted on waking and alert when you’re supposed to be going to sleep.

What symptoms are attributed to adrenal fatigue?

The symptoms which are attributed to adrenal fatigue are very general and can be experienced with other conditions.

  • Craving salt and sugar
  • Retaining fat around your middle
  • Low mood and depression
  • Brain fog
  • Fatigue
  • Weight gain
  • Body aches

What is the controversy around adrenal fatigue?

Adrenal fatigue would not normally be diagnosed by a conventionally trained doctor. Indeed, the Society of Endocrinologists has stated that adrenal fatigue is not even a medical condition and that there is no evidence that this condition exists. While there are conditions that do affect the adrenal glands like Addison’s Disease (primary adrenal insufficiency) and Cushing’s Syndrome (caused by the over-production of cortisol), there is no evidence that overloading the adrenal glands through stress causes any functional problems which could lead to adrenal insufficiency. In fact, most endocrinologists suggest the opposite, that when the body experiences stress, the adrenal glands increase their production of cortisol rather than reduce it.

How is adrenal fatigue diagnosed?

Adrenal fatigue is much more likely to be diagnosed by an alternative or natural health practitioner than by a GP or endocrinologist. In most cases they will treat it by natural methods such as nutrition and lifestyle, rather than a course of drugs or hormone replacement. They will typically use non-invasive saliva testing to assess cortisol rhythm – cortisol levels that remain flat all day or even rise at bed time would signal to them that the adrenal glands are impaired.

What are the risks of being diagnosed with adrenal fatigue?

Most alternative practitioners will treat adrenal fatigue through lifestyle changes aimed at reducing stress: establishing a good bedtime routine, getting a full night’s sleep, eating an unprocessed diet rich in vegetables and whole grains, taking time in the day to meditate and re-charge batteries and taking regular moderate exercise. This is sensible advice for anyone who is looking to improve their lifestyle and, because it advocates many healthy habits, can also improve symptoms associated with chronic stress. In some cases, they will recommend the use of supplements containing dried adrenal cortex. This contains the hormone hydrocortisone and can cause symptoms that resemble Cushing’s disease if excessive amounts are taken.

However, problems can arise if symptoms which are general and non-specific are attributed to adrenal fatigue when in fact they are early signs of something more serious or of another treatable condition. Conditions that may be attributed to adrenal fatigue because of similar symptoms include anaemia and thyroid problems. Please remember it is also always important to talk to your GP and rule out any more serious conditions before seeking an alternative diagnosis.

The gonads

Chapter 5

The gonads

The testes and the ovaries produce the hormones most likely to change over our lifetimes. From puberty to menopause, learn how these hormones affect libido, fertility and mood. 

The testes and the ovaries are both reproductive organs and endocrine glands. Find out about the reproductive hormones they produce and their role in male and female characteristics, the menstrual cycle and fertility.

The gonads are the glands in men (testes) and women (ovaries) which are responsible for producing gametes (sperm and eggs) for reproduction as well as the hormones which are responsible for male and female characteristics. They produce many of the same hormones but in different amounts.

What hormones are produced by the ovaries?

The ovaries are responsible for producing ova (eggs) as well as manufacturing hormones. The primary hormones produced by the ovaries are oestrogens and progesterone.


The ovaries produce 3 types of oestrogen – oestrone (E1), oestradiol (E2) and oestriol (E3). Of these oestradiol (E2) is the most potent; E1 and E3 are weaker forms of oestrogen. Oestrogens play an important role in the development of female secondary sex characteristics, the female reproductive system as well as a host of other bodily functions including bone formation, collagen production and mood regulation.

In females, oestrogen levels increase at puberty leading to the development of female secondary sex characteristics such as the development of breasts, the widening of the hips and the growth of pubic and underarm hair.

Oestrogen also plays a key role in the menstrual cycle – including the maturing and release of an egg at ovulation and preparing the uterine lining for fertilisation. Oestrogen levels increase in the first half of the menstrual cycle and then decline, triggering menstruation if the egg has not been fertilised. Low levels of oestrogen during menstruation then triggers an increase in FSH to prepare a new egg for ovulation. If an egg is fertilised, oestrogen levels continue to rise throughout pregnancy, developing the placenta to nourish the growing baby and preparing the breasts to produce milk. Oestrogen levels peak in the 3rd trimester and trigger the release of oxytocin by the hypothalamus which causes the womb to contract and labour to begin.


Progesterone is a steroid hormone which is made in the corpus luteum (the remains of the follicle after an egg has been released) in the second half of the menstrual cycle. Progesterone prepares the endometrium for implantation and, if implantation is successful, its level rises rapidly to maintain the pregnancy. The corpus luteum continues to make progesterone for the first 8 -12 weeks of pregnancy after which production switches to the placenta. As well as maintaining the health of the placenta to nourish the baby, progesterone causes changes in the body to accommodate the growing baby (e.g. the expansion of the womb and relaxation of ligaments) and prepare for childbirth (e.g. growth of milk ducts in the breasts). If the egg isn’t fertilised the corpus luteum breaks down and the production of progesterone drops, causing the menstrual cycle to start again.

What is the role of testosterone in women?

Although it is known as the male sex hormone, women also produce small amounts of testosterone both in the adrenal glands and the ovaries. Testosterone causes the bodily characteristics which are considered male, such as the deepening of the voice, growth of muscle, growth of facial hair and libido. In females, testosterone has a role in bone health, breast health, fertility and sex drive.

What can affect female hormones?

Polycystic Ovary Syndrome (PCOS)

Polycystic Ovary Syndrome, also known as PCOS, is a common hormone condition which affects about 1 in 5 women in the UK [1].

PCOS affects a woman’s ovaries, the reproductive organs that are responsible for protecting all the eggs that a woman is born with, and for releasing them into the fallopian tube for fertilisation. The ovaries are also responsible for producing oestrogen and progesterone, the hormones that regulate the menstrual cycle.

Normally, a woman’s ovaries produce an egg each month, but with polycystic ovaries (an imbalance in the reproductive hormones that govern ovulation) this process can be disrupted. During the monthly cycle FSH stimulates the ovary to produce a follicle – a sac to contain an egg, and then LH triggers the ovary to release a mature egg.

In a woman with PCOS, the ovaries and ovulation process are affected. Its three main features are:

  • Irregular periods
  • High levels of male hormones - androgens
  • Cysts in the ovaries

In polycystic ovaries, several small, fluid-filled sacs grow inside of the ovaries. These small sacs contain a number of harmless follicles that are up to 8mm in size. Each one of the follicles contains an immature egg which never matures enough to activate ovulation. The absence of ovulation changes the levels of oestrogen, progesterone, FSH and LH, making them lower than usual, while male hormone levels are higher than usual.

What causes PCOS?

The exact cause of PCOS remains a mystery, however it often runs in families [2]. It is also believed that an increase of male hormones prevents the ovaries from producing hormones and releasing eggs normally.

Factors which are thought to play a role in PCOS include:

  • Inflammation – women with PCOS often have increased levels of inflammation in their bodies which has been linked to higher levels of androgens [3]. Being overweight can also impact a woman’s inflammation levels.
  • Insulin resistance – it has been identified that 70% of women with PCOS have insulin resistance which means their cells can’t use insulin properly [4]. This means that more and more insulin is produced to try to move glucose from the blood into the body’s cells. This elevated insulin is thought to be one of that factors that causes polycystic ovaries to develop.


The symptoms of PCOS can vary from person to person. Many women experience very few symptoms, which can lead to some being unaware that they have PCOS. A study found that up to 70% of women with PCOS haven’t been diagnosed [5]. If symptoms are visible, women usually start to notice them around their first period, whilst others may only uncover they have PCOS after they have gained a lot of weight or have had trouble trying to get pregnant.

Common symptoms include:

  • Irregular periods or no periods at all
  • Excessive hair growth – usually on the face, chest or back
  • Weight gain
  • Difficulty getting pregnant due to irregular ovulation or failure to ovulate
  • Oily skin or acne
  • Hair loss or thinning on the head

PCOS has also been found to increase a woman’s risk of developing health problems in later life, such as type 2 diabetes and elevated cholesterol.

How PCOS can affect your body

Higher levels of androgens can impact your overall health in a variety of ways:

  • Infertility - As women with PCOS do not ovulate regularly or at all, the eggs that are required for fertilisation are not released making it difficult to become pregnant.

  • Sleep apnoea - A study found that women who are obese and have PCOS are 5 to 10 times more likely to develop sleep apnoea than those who don’t have PCOS [6]. The condition causes repeated pauses in breathing during the night, which can affect sleep.

  • Depression - Due to the hormonal changes and the difficulties PCOS presents such as unwanted hair and infertility, women can experience high levels of depression and anxiety [7].

How is PCOS diagnosed?

Many women report that getting a diagnosis for PCOS can be a struggle as there is no single test to identify whether you have it. Under NHS guidelines, doctors should confirm that a woman has two or more of the following;

  • high androgen levels
  • irregular menstrual cycles
  • cysts in the ovaries

Usually your doctor will send you to have an ultrasound scan and a blood test. The ultrasound scan uses sound waves to look for abnormal follicles and other problems with your ovaries and uterus. The blood test will check whether your male hormone levels are higher than normal.

How is PCOS treated?

There is no cure for PCOS, although symptoms can be managed by making lifestyle changes or taking medication [8].

  • Diet and lifestyle changes – treatment for PCOS often starts with lifestyle changes such as weight loss, diet and exercise. Studies have found losing just 5 to 10 percent of your body weight can help regulate your menstrual cycle and improve PCOS symptoms [9].
  • Medication – several medications can assist in regulating the menstrual cycle and treat PCOS symptoms such as hair growth and acne. Metformin can help to restore the menstrual cycle and Clomiphene, a fertility drug, can help women with PCOS get pregnant.
  • Surgery – if taking Clomiphene is not successful, a surgical procedure called laparoscopic ovarian drilling (LOD) can be performed. This involves using heat or a laser to destroy the tissue in the ovaries that is producing androgens.


Menopause occurs when a woman’s reserve of viable eggs runs out and is characterised by a rapid decline in oestrogen. Women can experience fluctuations in oestrogen for years before they stop menstruating altogether, normally around the age of 50. Menopause is defined as no menstruation for a year.

What are the symptoms of the menopause?

  • Hot flushes
  • Vaginal dryness
  • Weight gain
  • Night sweats
  • Reduced libido
  • Difficulty concentrating
  • Low mood or anxiety
  • Breast tenderness
  • Reduced bone mass
  • Hair thinning or hair loss
  • Insomnia
  • More frequent urinary tract infections

The symptoms of the menopause can start up to 10 years before a woman’s final period (perimenopause) and can continue for a decade after.

How is menopause diagnosed?

For women of menopausal age, diagnosis is normally made by an assessment of symptoms; menopause is not usually diagnosed with a blood test, as fluctuating hormone levels in the years preceding the menopause can give a misleading diagnosis. However, in women who are experiencing symptoms of menopause before their 45th birthday, a blood test to determine levels of FSH (which will be higher during menopause) and oestradiol (which will be lower) can indicate an early menopause.

As the symptoms of menopause are very similar to those of other conditions, especially an underactive thyroid (which is often first diagnosed in women of menopausal age), a thyroid blood test can also help to distinguish between menopausal symptoms and a thyroid disorder.

How are menopausal symptoms treated?

Many women go through the menopause without need for any treatment, but for some women the symptoms are very debilitating and can affect their quality of life. For these women, hormone replacement therapy (HRT) can do a lot to relieve symptoms. Most HRT is a combination of oestrogen and progesterone and can be taken by oral tablets, skin patches, gels or pessaries.

The testes

What hormones are produced by the testes?

The primary hormone produced by the testes is testosterone although they also produce small amounts of oestradiol. Testosterone levels increase significantly at puberty which leads to the development of secondary sex characteristics in boys such as lowering of the voice, development of muscle mass, increase in body and facial hair and the enlargement of the penis. Testosterone is responsible for libido, sperm production, mood and muscle mass all through adulthood. Testosterone levels typically peak when a man is in his 40s and then decline by around 1% every year.

What can affect testosterone production?

It is very rare for men to overproduce testosterone; it is far more common to have low testosterone levels than naturally high testosterone. Low testosterone (hypogonadsim) has many causes, typically through damage to the testicles (through injury or chemotherapy), medication or anabolic steroid use, or as a side effect of other conditions such as diabetes, liver disease or obesity. Low testosterone can also be caused by an inherited condition called Klinefelter Syndrome where the male is born with an extra copy of the X chromosome. Late onset hypogonadism is caused by falling levels of testosterone in older men.

What are the symptoms of low testosterone?

  • Low libido
  • Reduced muscle mass and inability to gain muscle in the gym
  • Erectile dysfunction
  • Infertility
  • Low mood and motivation
  • Small testicles
  • Difficulty sleeping
  • Low volume of semen
  • Low energy

How is low testosterone diagnosed?

Low testosterone is normally diagnosed by an assessment of symptoms and a blood test. As testosterone levels fall during the day, it is normally recommended that testosterone is tested in the morning before 10am.

How is low testosterone treated?

Low testosterone can be treated by reversing any lifestyle factors that may be causing it, e.g. sleeping better, losing weight and reducing alcohol, or by prescribing testosterone replacement therapy (TRT) which can restore testosterone to normal levels. Testosterone can be given orally, through injections or gels.

What is the role of oestradiol of men?

A small amount of oestradiol is made in the testes but testosterone can also be converted to oestradiol in the liver and fat tissues by the action of the aromatase enzyme. Oestradiol plays a role in sexual desire, the ability to achieve an erection as well as sperm production. While all men make oestradiol, in some men levels of oestradiol can be too high causing symptoms such as the growth of breast tissue (gynaecomastia), infertility and erectile dysfunction.

High oestradiol in men is often caused by having high levels of testosterone (usually by taking too much TRT or steroid misuse) which leads to more testosterone being converted to oestradiol. It can also be caused by obesity and through exposure to exogenous oestrogens e.g. plastics and phyto-oestrogens in food.

How can high oestradiol be treated?

High oestradiol may be treated by lifestyle adjustments e.g. losing weight and reducing alcohol consumption as well as keeping testosterone levels within normal levels. If high oestrogen persists you may be prescribed aromatase inhibitors which reduce the amount of testosterone that is converted to oestradiol.

Everything you need to know

Everything you need to know

“Your endocrine system tightly controls the amount of hormones in your body. If hormones go too high or too low then problems can follow”
Dr Sam Rodgers

Medical Director

The thyroid and the parathyroid glands.

Chapter 6

The thyroid and the parathyroid glands.

Too hot? Too cold? Losing weight or gaining it? Irritable and moody or just plain tired? Learn about the hormones that can affect your metabolism and overall wellbeing.

The thyroid and the parathyroid glands are located next to each other in the neck but, despite their name, that’s really all they have in common. Read on to find out more.

What is the thyroid gland and what does it do?

The thyroid gland is a butterfly shaped gland which wraps around the windpipe in the throat. It is responsible for producing the hormones thyroxine (T4) and triiodothyronine which affect the metabolic rate of the body. Thyroid hormones impact almost all bodily processes from how fast your heart beats, how much energy you have, how quickly you digest food to how sensitive you are to heat and cold. Elevated thyroid hormones cause your metabolism to run to fast (hyperthyroidism) and insufficient levels cause your metabolism to run too slowly (hypothyroidism).

What hormones does the thyroid gland produce?

  • Thyroxine (T4) - Thyroxine is the primary hormone produced by the thyroid gland but it has little direct influence on the body’s cells. It is a prohormone for triiodothyronine (T3) which is the more biologically active thyroid hormone. Thyroxine is converted to T3 in the liver and other organs of the body.

  • Triiodothyronine (T3) - Only around 20% of T3 is produced by the thyroid gland itself – the rest is converted from T4 by the deiodinase enzymes. T3 is the more biologically active thyroid hormone which directly affects the body’s metabolism.

What can go wrong with the thyroid gland?

Autoimmune thyroid disease

Autoimmune conditions cause the vast majority of thyroid disorders. In an autoimmune condition, the body mistakenly identifies its own cells as “foreign” and begins attacking them. In the case of a thyroid disorder, this autoimmune attack can cause the thyroid gland to over-produce thyroid hormone (Graves’ disease) which speeds up the metabolism, or destroys thyroid tissue which reduces its ability to produce thyroid hormones causing the metabolism to slow down (Hashimoto’s thyroiditis).

Secondary thyroid disease

In secondary thyroid disease, the problem does not lie with the thyroid gland itself, but with the signalling gland – the pituitary. A tumour in, or surrounding, the pituitary gland can cause thyroid stimulating hormone (TSH) to be over-produced which in turn stimulates the over-production of thyroid hormones (secondary hyperthyroidism). TSH can also be under-produced causing the under-production of thyroid hormones (secondary hypothyroidism).

What are the symptoms of thyroid disease?

Thyroid hormones affect almost every cell in the body and have wide-reaching effects on all of the body’s processes. Classic symptoms of an overactive thyroid include a faster heartbeat, sensitivity to heat, losing weight and diarrhoea, while an underactive thyroid causes the opposite – a slower heartbeat, sensitivity to cold, weight gain and constipation.

How is thyroid disease diagnosed?

Thyroid disease is normally diagnosed through an assessment of symptoms alongside a thyroid function blood test. A thyroid function blood test normally tests for thyroid stimulating hormone (TSH), free thyroxine (FT4) and sometimes, but not always, free triiodothyronine (FT3).

How is thyroid disease treated?

An overactive thyroid is normally treated by anti-thyroid medication such as carbimazole – or by removing or destroying all or part of the thyroid gland through surgery or radioactive iodine treatment. After the thyroid gland has been destroyed or removed, thyroid replacement hormones will need to be taken for life.

An underactive thyroid is treated by replacing the hormones that are no longer being produced by the thyroid gland. In most cases, this is achieved by replacing T4 (levothyroxine) which then converts into T3 as normal. In some people who don’t convert T4 to T3 effectively, a combination of T4 and T3 (liothyronine) will be prescribed.

The parathyroid

What are the parathyroid glands and what do they do?

Despite their name, the parathyroid glands have nothing to do with producing thyroid hormones; their name refers to the fact that they are located behind the thyroid gland in the neck. There are four parathyroid glands, each the size of a grain of rice, that are responsible for regulating calcium in the body. Calcium is a very important element in the human body and is necessary not only for strong bones and teeth, but also for the functioning of the nervous and muscular systems by providing electrical energy.

What hormone does the parathyroid gland produce?

Parathyroid hormone (PTH) - The sole job of the parathyroid gland is to regulate calcium within a tight range by the release of parathyroid hormone. If the glands sense that the level of calcium in the blood is too low they will release parathyroid hormone which extracts calcium from the bones. If they detect excess calcium in the blood they will stop the production of PTH.

What can go wrong with the parathyroid glands?

Hyperparathyroidism is the most common condition of the parathyroid glands and is normally caused by a benign tumour affecting one or more of the glands. This causes them to over-produce parathyroid hormone which means the body extracts more calcium from the bones than it needs and blood levels of calcium rise. The condition affects mostly women and is likely to be diagnosed between the ages of 50 and 60.

Hypoparathyroidism, where the body produces insufficient amounts of parathyroid hormone, is rare. It can develop if the parathyroid glands are damaged during surgery on the thyroid gland.

What are the symptoms of hyperparathyroidism?

Symptoms of high levels of calcium in the blood can come on suddenly or can develop over several years and are not always related to calcium levels. Some people can experience debilitating symptoms with only slightly raised blood calcium levels. Many of the symptoms are non-specific and may be confused with other conditions, especially if they are mild.

  • Fatigue
  • Aches and pains
  • Aching bones
  • Depression
  • Headaches
  • Heart palpitations
  • Irritability
  • Difficulty sleeping
  • Low libido
  • Memory loss and confusion
  • Kidney stones
  • Osteoporosis
  • High blood pressure
  • Feeling run down

How is hyperparathyroidism diagnosed?

The effects of elevated calcium levels are progressive meaning that symptoms like osteoporosis will get worse the longer the condition remains untreated. A diagnosis is made through the combination of an assessment of symptoms and a test to measure that amount of parathyroid hormone (PTH) and calcium in the blood.

How is hyperparathyroidism treated?

Treatment may begin with medication to lower calcium levels, but normally surgery is required to remove the affected parathyroid gland.

The pancreas, the pineal and the thymus

Chapter 7

The pancreas, the pineal and the thymus

From diabetes, your sleep-wake cycle to your immune function, these endocrine glands are vital to long-term health. Read on to understand why.

Find out about the endocrine glands that help metabolise food for energy, govern your circadian rhythm and turn your immature immune cells into mature, disease fighting T cells.

What is the pancreas and what does it do?

The pancreas is an abdominal organ which is responsible for producing enzymes that aid digestion as well as producing the hormones insulin and glucagon to regulate blood sugar.

  • Insulin - Insulin is produced by the beta cells of the pancreas when blood sugar (glucose) levels rise after eating and is necessary to get glucose from the blood into cells for energy. Insulin attaches to the body’s cells which “unlocks” them to absorb glucose. Insulin also enables excess glucose to be stored in the liver for future use.

  • Glucagon - Glucagon is produced by the alpha cells of the pancreas when it senses that blood glucose levels are too low. It signals to the liver to release stored glucose into the bloodstream while at the same time reducing glucose consumption by the liver to retain as much as possible in the blood.

What can go wrong with the pancreas?

Type 1 diabetes

The main condition which affects the ability of the pancreas to produce hormones is an autoimmune condition called type 1 diabetes. Type 1 diabetes occurs when the body’s immune system attacks the beta cells in the pancreas and impairs its ability to produce insulin. Type 1 diabetes is different from type 2 diabetes (diabetes mellitus), which normally develops later in life and is caused by the body’s cells becoming resistant to the effects of insulin. In both types of diabetes, glucose levels in the blood can become dangerously high –hyperglycaemia.

What are the symptoms of diabetes?

  • Extreme thirst
  • Frequent urination
  • Fatigue
  • Weight loss
  • Blurred vision
  • Slow-healing wounds
  • Frequent bouts of thrush

How is diabetes diagnosed?

Diabetes is normally diagnosed through a test to measure the amount of glucose in the blood or urine. A blood test may measure glucose levels after a fast overnight or may measure the amount of glucose that has attached the haemoglobin in the blood which gives a better long-term picture of blood glucose levels. Type 1 diabetes is commonly diagnosed in childhood, whereas type 2 diabetes is more commonly diagnosed in older adults and is usually lifestyle related – associated with obesity, sedentary lifestyles and poor diet.

How is diabetes treated?

People with type 1 diabetes will need to take insulin to control their blood sugar for the rest of their lives. In its early stages, type 2 diabetes or prediabetes may be controlled through lifestyle changes, in particular weight loss, a low-calorie diet and more exercise. Medications to lower blood sugar may also be prescribed (e.g. metformin). The longer someone has type 2 diabetes, the higher the probability that they will progress to need insulin to control their blood sugar in the future.

What is the pineal gland and what does it do?

The pineal gland is a small gland situated deep in the brain which is shaped like a pine-cone (from which it gets its name). The pineal gland governs the circadian rhythms of the body through the production of the hormone melatonin.

What hormone does the pineal gland produce?

Melatonin - Melatonin is responsible for governing the sleep-wake cycles of the body. It is sensitive to light, switching off production in daylight to promote wakefulness and producing higher levels when it is dark which promotes sleep. Night-time levels of melatonin are at least 10 times greater than during the day.

What can go wrong with the pineal gland?

The pineal gland can develop benign cysts and sometimes tumours. Pineal tumours are very rare but are most frequently diagnosed in children and adults under 40 years old. They normally require surgery to remove them.

What can affect melatonin levels?

Overproduction or underproduction of melatonin can affect the sleep cycle and can also impact mood. Chronic stress and a poor diet are also thought to impact the production of melatonin which can disrupt your sleep wake cycle. Tryptophan, an essential amino acid from food, is the precursor to melatonin and a diet low in tryptophan can supress melatonin levels. However, the main factor to affect melatonin production is light at night; even the dim light caused by a phone or computer in the bedroom can affect melatonin production.

How is low melatonin treated?

Improvements in lifestyle like removing any source of light from the bedroom, managing stress, and eating foods rich in tryptophan (such as seeds, pulses, chocolate, oats, dates and dairy products) can improve melatonin levels. Melatonin supplements are also available and are often used by people who fly frequently to manage jet lag.

What is the thymus gland and what does it do?

The thymus is both an endocrine (hormone producing) and lymphatic gland. It is glandular tissue that is located in the upper body behind the breastbone in the thoracic cavity. The thymus has an important role in immune function and is responsible for “training” T cells to fight infection by bacteria, viruses and fungi – T cells are also important in protecting the body against cancer. It is most active during childhood – by puberty the body has almost all the T cells it needs. The thymus continues shrinking through adulthood with glandular tissue being replaced by fat.

What hormone does the thymus gland produce?

The thymus produces thymosin, a hormone that stimulates the development of T cells.

What can go wrong with the thymus gland?

Problems with the thymus gland are associated with its immune function as opposed to its endocrine function. The three most common disorders of the thymus include myasthenia gravis, an autoimmune condition which attacks muscle receptors causing muscle weakness, red cell aplasia, when the immune system attacks the stem cells that form blood cells, and hypogammaglobulinemia, a condition where the body doesn’t make enough antibodies.


[1] NHS (2019). Polycystic ovary syndrome. [online] Available at:  [Accessed 23 Oct. 2019].

[2] Diamanti-Kandarakis, E., Kandarakis, H. and Legro, R. (2006). The Role of Genes and Environment in the Etiology of PCOS. Endocrine, 30(1), pp.19-26.

[3] González, F. (2012). Inflammation in Polycystic Ovary Syndrome: Underpinning of insulin resistance and ovarian dysfunction. Steroids, 77(4), pp.300-305.

[4] Marshall, J. and Dunaif, A. (2012). Should all women with PCOS be treated for insulin resistance?. Fertility and Sterility, 97(1), pp.18-22.

[5] March, W., Moore, V., Willson, K., Phillips, D., Norman, R. and Davies, M. (2009). The prevalence of polycystic ovary syndrome in a community sample assessed under contrasting diagnostic criteria. Human Reproduction, 25(2), pp.544-551.

[6] Ehrmann, D. (2012). Metabolic dysfunction in PCOS: Relationship to obstructive sleep apnea. Steroids, 77(4), pp.290-294.

[7] Cooney, L. and Dokras, A. (2017). Depression and Anxiety in Polycystic Ovary Syndrome: Etiology and Treatment. Current Psychiatry Reports, 19(11).

[8] The American College of Obstetricians and Gynaecologists (2017). Polycystic Ovary Syndrome (PCOS) - ACOG. [online] Available at:  [Accessed 23 Oct. 2019].

[9] Teede, H., Deeks, A. and Moran, L. (2010). Polycystic ovary syndrome: a complex condition with psychological, reproductive and metabolic manifestations that impacts on health across the lifespan. BMC Medicine, 8(1).

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Hormone FAQs
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