Thyroid disorders disproportionately affect women, especially during childbearing years. Many people live with thyroid conditions for several years without a diagnosis. However, thyroid problems often arise when women are trying to become pregnant and struggling to conceive. What is more, having an undiagnosed thyroid problem can make fertility treatments unsuccessful. Ahead, learn more about hypothyroidism in pregnancy and what to know if you are thinking about conceiving or undergoing any fertility treatments.

Why does the thyroid matter?

The thyroid is a small endocrine gland located at the base of the neck that makes and releases thyroid hormones throughout the body. These hormones are responsible for controlling the body’s metabolism. The two primary thyroid hormones are called thyroxine (T4) and triiodothyronine (T3). These hormones attach to receptor sites on all the cells in your body to deliver specific messages. Some of its most important roles include regulating metabolism, growth, and development.

Because thyroid hormones attach to every cell in your body, every system in your body can be affected by a poorly functioning thyroid. As you may imagine, the thyroid also affects reproductive functioning, which is especially apparent in women because the thyroid can throw off the menstrual cycle and ovulation. When these processes get interrupted, it can make conception and pregnancy quite challenging.

Two main conditions can affect your thyroid: hypothyroidism and hyperthyroidism.


The most common thyroid disorder is hypothyroidism, a condition in which the thyroid does not produce enough thyroid hormones. The most common cause of hypothyroidism is an autoimmune thyroid disease called Hashimoto’s thyroiditis. With Hashimoto’s thyroiditis, the immune system produces TPO antibodies that mistakenly attack your thyroid gland, causing inflammation and eventual thyroid failure.

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People with hypothyroidism have an underactive thyroid gland, meaning the gland does not produce enough thyroid hormone to support the body’s metabolic needs. When thyroid hormone levels are too low, the metabolism slows down.

Common symptoms of hypothyroidism include:

  • Fatigue
  • Increased sensitivity to cold
  • Constipation
  • Dry skin
  • Weight gain
  • Puffy face
  • Hoarseness
  • Muscle weakness
  • Elevated blood cholesterol level
  • Muscle aches, tenderness, stiffness
  • Joint pain, stiffness, or swelling
  • Heavy or irregular menstrual periods
  • Infertility
  • Thinning hair
  • Slowed heart rate
  • Depression
  • Impaired memory
  • Enlarged thyroid gland (goiter)


The exact opposite of hypothyroidism is hyperthyroidism, where the thyroid releases too much thyroid hormone, which causes the metabolism to speed up.

Common symptoms of hyperthyroidism include:

  • Nervousness, restlessness, and irritability
  • Rapid, irregular, and pounding heartbeat
  • Diarrhea
  • Unintentional weight loss
  • Increased appetite and thirst
  • Menstrual changes, including lack of periods
  • Goiter

Graves’ disease is the most common cause of this overactive thyroid state. Like Hashimoto’s, this condition is also an autoimmune thyroid disorder.

How the thyroid gland impacts fertility and pregnancy

Either too much or too little thyroid hormone can affect your menstrual pattern. Women who do not have a regular menstrual period often struggle to conceive. This happens because ovulation often does not occur, or if it does, it is not always when you would normally expect it.

The following are other reasons why thyroid dysfunction can impact fertility:

Thyroid hormones impact sex hormones

Firstly, thyroid hormones work very closely with the sex hormones estrogen and progesterone. Abnormal thyroid levels can disrupt normal levels of these hormones, throwing off the body’s ability to conceive and maintain a pregnancy. Even if fertilization does occur, there can be problems with implantation in the uterine wall, especially when progesterone levels are abnormal.

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Thyroid conditions affect metabolic demand

Secondly, because the thyroid plays an integral role in supporting metabolism, energy is first used to support your primary functions like maintaining homeostasis. Therefore, if other systems in your body are not functioning optimally, your body will not have enough energy to allocate to reproduction.

Autoimmunity causes inflammation

Thirdly, most thyroid diseases are rooted in autoimmunity. Chronic inflammation is at the root of all autoimmune disorders. While conditions like Hashimoto’s only attack the thyroid gland, your immune system may also cause inflammation in other tissues. Indeed, autoimmune diseases often present in multiples, where one person likely has more than one autoimmune disorder (polyautoimmunity).

In general, women with hypothyroidism or hyperthyroidism can experience:

  • A disrupted menstrual cycle
  • Anovulation, or disruptions in ovulation
  • Higher risk for miscarriage, and
  • Higher risk for premature birth
  • Impact of thyroid dysfunction on male fertility

Of course, thyroid problems can also affect male fertility. Thyroid hormones play a role in the development and function of the testes. Men with hyperthyroidism (an overactive thyroid) may experience reductions in semen volume, sperm density, and sperm motility (how efficiently the sperm move). Both hyperthyroidism and hypothyroidism (an underactive thyroid) may affect the size and shape of sperm. People with testes can reverse thyroid-related fertility issues once thyroid hormone levels are stabilized with treatment.

What to know about your thyroid if you are undergoing fertility treatments

Get your labs checked

If you struggle to conceive, you may want to consider taking an at-home thyroid blood test, including thyroid-stimulating hormone (TSH), free T4, and free T3. These tests alone are pretty revealing about your overall thyroid health. However, if any lab values are abnormal or even slightly abnormal, you may need thyroid treatment. Remember, thyroid conditions are commonly diagnosed in women of childbearing age, so it is one of the first things you and your doctor should rule out before proceeding.

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Take thyroid medication

Suppose your thyroid lab results indicate poor thyroid function. In that case, you will want to work with a thyroid doctor or endocrinologist (a doctor specializing in endocrine glands like the thyroid) to return your thyroid hormone levels to normal. Having an underactive thyroid is the most common problem, but fortunately, it is relatively straightforward to treat. If your TSH is high and your T4 is low, your doctor will likely put you on thyroid hormone replacement medication to help you reach a euthyroid state.

It can take some time for your thyroid hormone levels to stabilize once you find the correct medication dose. Still, once they do, you will probably see your periods return to normal unless you have something else disrupting your cycle.

Consider treating subclinical hypothyroidism

Sometimes TSH levels are within normal limits, but they are on the upper end of normal. This may be a sign of subclinical hypothyroidism. It may be enough of a problem requiring treatment, especially if you undergo IVF and other infertility treatments. Please consult with your thyroid doctor about this option.

Optimizing your thyroid levels with thyroid hormone replacement medication is one step you can take to improve conception and healthy pregnancy chances. When choosing thyroid medication with your doctor, remember that there is no one-size-fits-all treatment.