Thyroid and Your Fertility 

November 13, 2019 | Yesmom

Yes Mom

It’s important to take the necessary tests to check your thyroid levels, especially thyroid-stimulating hormone (TSH) and Free thyroxine (fT4). Thyroid disorders such as hypothyroidism, hyperthyroidism or other associated medical conditions, such as Polycystic Ovarian Syndrome (PCOS) can affect fertility negatively. 

But no worries, once diagnosed correctly these conditions can usually be treated with medications and positive lifestyle changes. So get proactive and learn more about the thyroid gland and its common disorders that may impact fertility.

The Highlights


  • The thyroid gland has a major impact on fertility. But, don’t worry, infertility due to thyroid disorders can usually be resolved by balancing the production of thyroid hormones.
  • The thyroid gland helps regulate many body functions including metabolism, body temperature, and even the menstrual cycle.
  • The thyroid gland produces the hormones T3 and T4 in response to the thyroid-stimulating hormone (TSH).
  • Unbound/free thyroid hormones, Free T4 tests help to evaluate thyroid function and diagnose thyroid disorders.
  • Hypothyroidism occurs when thyroid hormones are too low and this can cause many health problems including fertility issues.
  • Overproduction of thyroid hormones leads to hyperthyroidism which, in turn, may cause menstrual irregularities.
  • Polycystic Ovarian Syndrome (PCOS) is an infertility problem commonly associated with thyroid disorders.

Understanding TSH and Free T4

The thyroid is a butterfly-shaped gland located at the base of your neck. It produces the hormones T3 and T4 in response to the thyroid-stimulating hormone (TSH) released by the pituitary gland. These hormones have a major role in the body’s metabolic rate, brain development. heart and digestive function, mood, muscle control, and bone maintenance. Your thyroid gland has a powerful impact on your menstrual cycle and fertility as well since these hormones send signals to your ovaries to ovulate each month. 

Thyroxine (T4) is the main form of thyroid hormone in our blood and it is converted to the active T3 in our cells. But, just measuring the total thyroxine in your blood can be misleading as thyroid hormones are bound to carrier proteins known as Thyroxine-binding globulin (TGB) for circulation. Such bound thyroid hormones are not active. Only a minute percentage of these hormones are unbound/free and testing the amount of this Free T4 is what helps diagnose thyroid imbalances.

If the thyroid hormone production is too high or too low, this imbalance can result in many health problems, including fertility issues such as irregular periods, ovulatory disorders, preterm births, etc. For pregnant women, it increases the chances of miscarriage and the development of the fetus may also get affected.

Common Thyroid Disorders Associated With Fertility

Hypothyroidism: If your TSH value is too high (above 4 mU/L ), then you may be suffering from hypothyroidism. This means the pituitary gland in the brain is sending more stimulating hormones to the thyroid, to increase it’s production, as your thyroid hormones are too low. Symptoms often seen in those suffering from hypothyroidism include low energy, fatigue, depression, weakened muscles, constipation, dry skin, weight gain and intolerance to cold. Hypothyroidism may cause difficulties in conceiving a baby. It may lead to low basal body temperature and menstrual cycle abnormalities such as infrequent menstrual cycles, heavier bleeding, etc. 


Hyperthyroidism: Overproduction of thyroid hormones results in hyperthyroidism, in which case, the thyroid-stimulating hormone levels will fall below normal values (below 0.4 mU/L). A rapid heart rate, anxiety, weight loss, brittle hair, intolerance to heat are just a few symptoms of hyperthyroidism. Hyperthyroidism can cause menstrual cycle irregularities and loss of libido


Polycystic Ovarian Syndrome: Polycystic Ovarian Syndrome (PCOS) is another infertility problem that is commonly associated with thyroid issues. Both of these infertility issues result from abnormal hormonal levels. If you have been diagnosed with both hyper/hypothyroidism and PCOS, there is no reason to despair. These can usually be corrected by balancing the hormones, significantly improving your chances of having a baby.

These symptoms may be due to other fertility issues. It can be challenging to find the root cause of such symptoms. Ruling out thyroid as the culprit can help you continue on with your investigation to understand and treat the underlying cause of your infertility. Most causes of infertility such as thyroid imbalances can be corrected if diagnosed correctly and in time. A simple blood test can be used to spot most thyroid abnormalities such as hyperthyroidism and hypothyroidism. PCOS diagnosis usually requires ultrasound scans of the ovaries as well as blood tests to measure hormones such as estrogen and testosterone.

For men, hypothyroidism can cause a variety of fertility problems such as low levels of testosterone, lower libido, trouble with sustaining an erection, reduced sperm volume, decreased sperm motility and so on. So if a couple has trouble conceiving, then the male partner should not only do the recommended fertility tests but also run a complete thyroid panel.

Treating Infertility Due to Thyroid Problems

Treating infertility that stems from thyroid issues start with stabilizing thyroid hormones. People suffering from hypothyroidism are usually prescribed levothyroxine to correct their problems. Treating hyperthyroidism is a bit more complicated and may include treatment with radioactive iodine, medications such as methimazole and propylthiouracil, or even surgery to remove the thyroid gland. A myriad of symptoms can occur while the thyroid levels equilibrate, but most of these symptoms get resolved once the hormone levels are balanced.

Once treated, hormone levels in moderate thyroid issues usually get restored within a few months. If there are no additional medical issues, you may conceive naturally once the hormonal levels have stabilized. Further infertility treatments are considered only if other medical complications are present or if natural conception does not occur even after a year of having normal thyroid hormone levels.

In the meantime, there are many things that you can do to help improve your health and fertility. Excess weight often causes hormonal imbalances and can disrupt ovulation in women. It is also important to keep your stress levels low as stress contributes to both hormonal imbalance and weight gain. You should try to follow a healthy nutritious low-calorie diet and exercise regularly to reach and maintain a healthy weight.