Hyperthyroidism (overactive thyroid) means that the thyroid gland produces and releases more thyroid hormones (T3 and T4) than your body needs. Your thyroid is an organ at the bottom front of your neck shaped like a butterfly. The thyroid’s main function is to control metabolism, but it has a big impact on the menstrual cycle and fertility too. Hyperthyroidism is much more common in women than in men, affecting around 1-2% of women.

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Impact of hyperthyroidism on fertility

The thyroid hormones influence a number of important reproductive hormones, including FSH, LH, estrogen, androgens, progesterone, and prolactin. Having an excess of thyroid hormones can make conception more of a challenge because it disrupts the cycle, suppresses ovulation, and causes irregular or missed periods. Hyperthyroidism can also lead to complications during pregnancy, including high blood pressure late in pregnancy, premature delivery, low birth weight, or miscarriage.

Diagnosis of hyperthyroidism

To be diagnosed with hyperthyroidism, you need to have low levels of TSH and high levels of thyroid hormones (T3 or T4). Subclinical hyperthyroidism is characterized by normal levels of thyroid hormones and low TSH.

Potential causes of hyperthyroidism

Hyperthyroidism can be due to the following things:

  • Graves’ disease, a genetic autoimmune disorder where your immune system attacks the thyroid gland. This is the cause about 85% of the time.
  • A growth of cells in your thyroid (thyroid nodules)
  • Inflammation of the thyroid gland (thyroiditis) 
  • Excess iodine consumption through diet or medication

Symptoms of hypothyroidism

Hyperthyroidism can cause the following symptoms:

  • Light, irregular, and missed periods (amenorrhea)
  • Weight loss
  • Fast or irregular heartbeat
  • Nervousness and irritability
  • Trembling hands
  • Heat sensitivity
  • Sleeping problems
  • Sweating
  • Thin hair and skin
  • Weak muscles
  • Enlarged thyroid

Treatment to improve fertility

The good news is that it’s easy to manage thyroid problems with medication. Drugs include antithyroid drugs methimazole or propylthiouracil, which stop your thyroid from over-producing hormones. Radioactive iodine shrinks the thyroid. Less commonly, the thyroid may be surgically removed.

Once the thyroid hormones are back in balance, fertility should return and you should be able to have a healthy pregnancy. It’s important to note that methimazole and radioactive iodine aren’t safe for the baby during pregnancy, so you’ll need to switch to a different treatment before you get pregnant if either of those were part of your therapy plan. 

Besides medication, there are a few things you can do to help with hyperthyroidism. For one, ensuring you have enough vitamin D helps keep your thyroid healthy and may decrease thyroid antibodies. Iron and zinc are other minerals linked to thyroid health.

In addition, note that the mineral iodine helps your body produce more thyroid hormones, so it’s helpful to have a diet low in iodine when your thyroid is overactive. Opt for non-iodized salt and reduce your intake of seafood (as it’s the food with the highest amount of iodine). Cruciferous vegetables, including broccoli, Brussels sprouts, cauliflower, and kale may help with hyperthyroidism too. 

Once you get pregnant, it’s important to let your OB-GYN know that you have hyperthyroidism. Your medication dosage will likely need to be adjusted and you’ll need to be more closely monitored during your pregnancy.

This article has been verified by a medical professional

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