THYROID DISEASE AND FERTILITY

Thyroid hormones interact with other, mainly reproductive, hormones.¹ A normally functioning thyroid gland or adequate replacement hormones are essential for ovulation, egg implantation and maintenance of a healthy pregnancy.¹

About thyroid problems and fertility

While infertility can be triggered by various factors, suboptimal function of the thyroid gland can also result in infertility, especially if thyroid disease runs in your family.¹ Once the thyroid disorder is treated then you should no longer face fertility problems, providing the thyroid was the only reason for infertility.¹

Know the facts

Thyroid hormones interact with other, mainly sexual, hormones.¹ The right amount of thyroid hormone is necessary for normal function of the testes in men and of the ovaries in women necessary to obtain normal fertility.¹ Too much (overactive thyroid) or too little (underactive thyroid) of these hormones can adversely affect male and female fertility.¹ Optimal function of the thyroid gland is not only beneficial to the health of the parents — it is also crucial for the health of the baby.² Suboptimal thyroid levels are a cause of fertility problems, increase the risk for miscarriage, premature delivery and other complications, and may impair brain development in the fetus, present in hypothyroidism too.² Male infertility is involved in one third of couples’ inability to achieve pregnancy, while one-third of cases are related to female causes and in the remainder there are issues with both the man and woman or no cause can be identified.³

If you have been unsuccessfully trying to fall pregnant for longer than a year, ask your doctor to check your thyroid hormone status before starting other medical procedures.³ If the thyroid is the cause of your infertility, getting it under control could restore fertility and reduce your risk for health complications.¹

A simple blood test, at first, can detect the amount of thyroid hormones (thyroxine and triiodothyronine) that your thyroid is secreting.⁴ Your doctor will be able to quickly tell you if you have hypothyroidism or hyperthyroidism.

Get your thyroid gland checked if:

• You have been trying unsuccessfully to get pregnant for more than 12 months³
• You have had two or more miscarriages³
• You have irregular menstrual cycles³
• You have any family history of infertility problems³
• You have a low sperm count or a history of testicular, prostate or sexual problems³

How thyroid hormones impact male fertility

Thyroid hormones, which were previously thought not to affect male fertility, are now being recognized as having an important role in, for example, sperm production.¹ The good news: correction of these disorders may restore a man’s fertility.¹

The overactive thyroid

If your thyroid gland produces and releases excess thyroid hormones into the bloodstream then you have hyperthyroidism.⁴ Men can develop hyperthyroidism for a number of reasons, including Graves’ disease, overmedication with thyroid hormones for treatment of hypothyroidism, and the presence of thyroid nodules or an inflamed thyroid gland (known as thyroiditis).⁴ By speeding up your body’s metabolism, hyperthyroidism can result in many different symptoms, some of which are often mistaken for simple nervousness due to stress.⁴

If you are having fertility problems and also have some of the symptoms of hyperthyroidism (it is unlikely you would develop all of them) then you should bring up thyroid disease with your doctor, especially if you have a family history of thyroid disease.⁴

The underactive thyroid

If your thyroid gland produces insufficient thyroid hormones then you have thyroid deficiency, medically known as hypothyroidism.⁵ The most common causes of hypothyroidism are iodine deficiency and, where iodine deficiency is uncommon, Hashimoto’s disease, an autoimmune disease that progressively destroys your thyroid gland.⁵ Thyroid deficiency slows down your metabolism. Poor thyroid function is often associated with reduced libido and erectile dysfunction; furthermore, it has an adverse effect on the form and structure of sperm — all of which can give rise to infertility.¹

If you are experiencing fertility problems and also have some of the symptoms of hypothyroidism then you should tell your doctor about your symptoms.

How thyroid hormones impact female fertility

Thyroid hormones interact with a woman’s reproductive hormones, estrogen and progesterone, to preserve normal function of the ovaries and maturation of the egg (oocyte).¹ If your thyroid gland releases too many (hyperthyroidism) or too few (hypothyroidism) thyroid hormones then the balance of reproductive hormones can be impaired,¹ with resulting thyroid-related fertility problems such as ovulation disorders, irregular periods and reduced fertility.¹ Since thyroid disease is a common endocrine disorder in women of childbearing age, the first thing to do when you have trouble getting pregnant is to have your thyroid checked, especially if thyroid disease runs in your family.⁴

The overactive thyroid

Hyperthyroidism is 10 times more common in women than in men⁶ and can cause a woman to have difficulties in not only getting pregnant, but also staying pregnant.¹ If your thyroid gland releases excessive amounts of thyroid hormones into the bloodstream then you are hyperthyroid.⁴ The most common reason for hyperthyroidism in young women is Graves’ disease, an autoimmune disorder in which antibodies mistakenly attack the thyroid gland, this stimulates the gland to overproduce thyroid hormones.⁴ If you experience unhealthy weight loss, this can also hamper your chances of falling pregnant.³

If hyperthyroidism is at the root of your infertility, proper treatment with a resulting optimal thyroid-stimulating hormone (TSH) level (TSH stimulates the thyroid to produce thyroid hormones) usually corrects the disturbance.¹ If you are at the right TSH level but still have problems getting pregnant then you may need to consult with an endocrinologist who specializes in reproductive disorders. See also www.fertility.com.

The underactive thyroid

If you have a family history of thyroid disease or any autoimmune disease then you will be at increased risk for hypothyroidism.⁷ If your thyroid gland produces too few thyroid hormones, your TSH levels will increase to stimulate your thyroid gland to fill up the gap. Elevated TSH has been observed in around 5% of cases of pregnant women.⁸

Women who are hypothyroid may have infrequent and light menstrual bleeding, no menstrual cycles or irregular cycles due to problems with ovulation.¹ The prevalence of autoimmune thyroid disease is higher in people with polycystic ovarian syndrome (PCOS),⁹ a condition that causes cysts on the ovaries and may lead to infertility or pregnancy complications .¹⁰

Treatment for thyroid-related infertility

If you have hypothyroidism then your thyroid gland produces insufficient thyroid hormones.⁷ If this is the case, you may simply have to take appropriate medication every day.⁷ Appropriate medication may normalize menstrual irregularities in women and sperm abnormalities and erectile dysfunction in men, and can restore fertility.¹

If you have hyperthyroidism, treatment will be tailored to the specific cause and may include medication, radioactive iodine therapy or surgery.¹¹ In women, the application of radioactive iodine treatment before pregnancy usually eliminates the need for anti-thyroid drugs. A woman should wait 4–6 months after radioactive iodine treatment before trying to become pregnant.¹² Men who have had radioactive iodine treatment should wait 3–4 months before attempting to get their partner pregnant.¹²

Note: If you have “normal” thyroid function or your thyroid and TSH levels are regulated by treatment and you still don’t get pregnant, you should consult a fertility specialist for advice and additional treatment. See also www.fertility.com.

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Date of preparation: February 2022