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Why are women more prone to thyroid conditions?

Why are women more prone to thyroid disorders? Is the answer in your X chromosomes?

Have you ever wondered why women are more prone to thyroid conditions? You may have asked around and even heard a few theories. Nonetheless, the actual reason seems to remain quite a mystery.

As many as one in 20 people have a thyroid condition [1], but women are five to ten times more likely to experience a condition with their thyroid gland.The two types of thyroid conditions are hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid).

What causes a thyroid condition?

Most thyroid conditions are caused by an autoimmune disease. You can also develop a thyroid condition from side effects to medications like amiodarone or inflammation from a viral infection.

Autoimmunity occurs when your immune system attacks parts of your own body. Autoimmune disorders (AD) have often been shrouded in mystery, leaving patients frustrated and doctors confused. In recent years, however, there’s been much research into the origins of AD.

The main autoimmune conditions that affect your thyroid are:

  • Hashimoto's thyroiditis, which causes hypothyroidism
  • Graves' disease, which causes hyperthyroidism

While there isn’t a cure for either of these, they can be managed with the right treatment plan – so getting tested is important. Your doctor will take your symptoms into account alongside doing some thyroid blood tests to give you a diagnosis of a thyroid disorder.

Your immune system is heavily involved in the progression of both diseases. Research has found that if you have one autoimmune condition, you’ll be prone to developing more. Somehow, your body is vulnerable to being attacked by its defence system. 

Now, we’ll discuss two theories as to why women are more likely to develop autoimmune thyroid conditions: double X chromosomes and X chromosome inactivation.

The genetic origins of autoimmune disorders

The blueprint of our entire body is in our DNA, long-chain molecules that contain all the coding needed to keep our bodies running. DNA is cleverly stored in your cells by tightly folding into themselves to form structures called chromosomes. When cells need to make new proteins to function, they’ll open up segments of the chromosomes to access the DNA inside.

All our cells have 23 pairs of chromosomes, whereas sperm cells and egg cells only carry half that number. That means we get half our genes from mum and the other half from dad.

The 23rd pair of chromosomes are the sex chromosomes, the X and Y chromosome. Biological females have two X chromosomes (XX), and males have an X and a Y (XY). The X chromosome is very big, carrying around 900 genes, whereas the Y chromosome only contains 55 genes. 

The X chromosome contains many genes that are related to the immune system. Where there are more genes, there is a greater risk of genetic mutations. Your cells are usually good at correcting genetic slip-ups and getting rid of faulty proteins, but sometimes these mutations can avoid detection.

As women have two X chromosomes, this risk of mutations is doubled compared to men. This can potentially predispose women to faults in the immune system, leading to autoimmunity.

X chromosome inactivation

The female foetus undergoes a genetic process called X chromosome inactivation when inside the mother’s womb. We don’t need both copies of the genes in the X chromosome, so our cells will randomly switch off either copy of the X chromosome. 

In each cell, you’ll either have mum or dad’s X chromosome switched off. In general, cells will have a 50:50 ratio of parental X chromosomes. This also contributes to how you might look like your mum but have other characteristics from your dad.

Some people can have a skewed ratio of this X inactivation, even going as far as an 80:20 ratio. If you have more of a skew towards your maternal chromosome, then your immune system will struggle to recognise the cells with your paternal chromosome. When triggered, your immune system can attack those cells. This is a strong theory in research for systemic lupus erythematosus (SLE), but it’s interesting to note as it accounts for the gender bias in AD.

Developing an autoimmune thyroid disorder comes from a combination of genetic factors and environmental triggers. It is well established that we all can carry the potential genes for certain diseases and disorders. Changes throughout life can trigger these diseases (for example, high levels of stress).

Pregnancy and menopause

Women can typically go through three major changes to their bodies: puberty (menarche), pregnancy, and menopause. Each stage carries subtle transformations, often caused by hormonal fluctuations. 

There are three main hormones found in women that can affect autoimmunity:

  • Oestrogen
  • Progesterone
  • Prolactin (needed for breastfeeding)

During pregnancy, your level of all three hormones increases exponentially. 

You need more oestrogen to support your developing baby and your changing body. Oestrogen promotes the protection of your cells by enhancing your immune system. However, if your autoimmune condition involves antibodies, you might find your symptoms worsening. 

Progesterone is useful in suppressing your immune system, which can balance the effect of oestrogen. Prolactin has pro-inflammatory effects, which boosts the levels of inflammation in your body. If your autoimmune condition is susceptible to inflammation, you might see worsening symptoms due to prolactin.

During menopause, your levels of oestrogen drop dramatically as your ovaries are no longer releasing eggs. You’ll still have a background level of oestrogen as it won’t disappear completely, but at low levels, oestrogen can trigger pro-inflammatory processes.

Women go through many changes with their hormones. From large-scale changes like pregnancy or menopause to smaller fluctuations throughout their menstrual cycle, the landscape of a woman’s hormones is always in flux. This impacts immunity in ways that we are still trying to understand. When compared to men, the very DNA of women’s bodies can leave them susceptible to autoimmunity.

Men aren’t exempt from thyroid conditions 

While thyroid conditions are more common in women, men are not immune. Untreated thyroid conditions can affect mental health, muscle mass and even fertility.

The symptoms of thyroid conditions in men are similar to those in women. These include:

  • Fatigue
  • Irritability
  • Mood changes
  • Weight changes
  • Sensitivity to hot or cold environments

In hyperthyroidism, the increased levels of thyroid hormone can cause a decrease in testosterone. Both men and women have testosterone, but the levels in men are about ten times higher. 

Men need testosterone for many different functions. A decrease in testosterone can affect a man’s muscle mass and sexual function, in particular leading to erectile dysfunction

Thyroid disorders can also impact fertility in men and women. In men, it may disrupt sperm production and sperm motility. This can cause difficulties in trying to have a baby.

While thyroid problems may be more common in women, it’s important not to overlook that men can be affected, too. Both chronic stress and poor diet habits can impact autoimmune conditions. Taking measures to manage your stress and change your lifestyle to benefit your health will improve your autoimmune condition.

Thyroid blood tests

Medichecks has three popular tests that can help you understand whether a thyroid disorder is causing your symptoms.

  1. Our Advanced Thyroid Function Blood Test takes a detailed look at your thyroid function, including antibodies and thyroid nutrition, for optimum thyroid health.
  2. Our Thyroid Function Blood Test is a simple at-home test. It checks your thyroid-stimulating hormone (TSH), free T3 (FT3) and free T4 (FT4) to see if you have the right level of thyroid hormones for a healthy metabolism.
  3. Our Thyroid Function with Antibodies Blood Test checks your thyroid-stimulating hormone (TSH), free T3 (FT3) and free T4 (FT4), as well as thyroid antibodies, for an in-depth picture of your thyroid health.

If you’re unsure, head over to the thyroid test buying guide for more information. 


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