Infertility and Thyroid Disease
Medically reviewed by Do-Eun Lee, MD
A thyroid disorder can be a cause of infertility in males and females, and once it's managed successfully, most couples are able to move forward with their plans to begin a family.
Related Fertility Issues
Research has linked both hyperthyroidism (often due to Grave's disease) and hypothyroidism (which typically results from Hashimoto's thyroiditis) to a number of issues that can interfere with fertility in women and in men.
In Women
For women, issues with the thyroid gland can manifest in several different ways that affect fertility.
Menstrual cycle abnormalities: Hypothyroidism in women has been linked to oligomenorrhea (infrequent menstruation) with periods that are more than 35 days apart. By contrast, an overactive thyroid or thyrotoxicosis (excess thyroid hormone in the blood) is associated with hypomenorrhea (short periods with a very light flow) and polymenorrhea, in which regular bleeding occurs at intervals of fewer than 21 days.
Disruptions in ovarian function: Low levels of thyroid hormone can interfere with ovulation (the monthly release of an egg from an ovary), causing anovulatory cycles—menstrual cycles during which an egg is not released.
Polycystic ovary syndrome (PCOS): This endocrine disorder affects approximately 10 percent of women of childbearing age and is the leading cause of ovulatory infertility. It's characterized by higher-than-normal levels of androgens (male hormones such as testosterone), which causes irregular, absent, or heavy periods that, in turn, affect ovulation. Hypothyroidism is increased in women with PCOS, but it is unclear why and more research is needed to understand the effects of thyroid dysfunction on fertility in women with PCOS.
Shortened luteal phase: This is the period of time between ovulation and menstruation. When this time period is compressed, a fertilized egg may be expelled during menstruation before it has a chance to implant and before a woman is aware that conception has taken place.
Imbalances in estrogen and progesterone: Normal levels of both hormones are essential for fertility.
Learn More: Thyroid Disease Symptoms
In Men
The ways in which thyroid disease can have an impact on male fertility have only recently been recognized and aren't fully understood.
Some include:
Low testosterone levels: A deficiency of this hormone in the blood can affect the development of sperm.
Imbalances in blood levels of sex hormone-binding globulin (SHBG): Also known as testosterone-estrogen binding globulin (TeBG), this protein, which is produced by the liver, plays a key role in transporting testosterone, dihydrotestosterone (DHT), and estradiol. In men who have hypothyroidism, levels of SHBG may be lower than normal; hyperthyroidism can cause SHBG levels to be too high.
Abnormalities of sperm and semen: In studies, hypothyroidism has been found to compromise sperm motility (how well sperm are able to move), sperm morphology (the shape of sperm), and semen volume (the amount of ejaculate a man produces). Hyperthyroidism has also been shown to affect sperm quantity and quality. This is important because if sperm motility, quantity, or quality is affected, it will be more difficult to fertilize the egg.
Hyperthyroidism in men also affects sexual function in a variety of ways, including decreased libido, erectile dysfunction, and premature ejaculation. None of these conditions causes male infertility, but they can make it difficult for a couple to get pregnant.
Learn More: Sexual Dysfunction and Thyroid Disease
Diagnosis
Infertility is diagnosed when a couple has been unsuccessfully trying to get pregnant by having unprotected intercourse for a year. This is the point at which most are advised to see a fertility specialist.
Because female fertility drops dramatically with age, females who are 35 or over typically are advised to see a reproductive specialist after six months of trying to conceive, and those over 40 may want to see a fertility doctor before even trying.
In order to zero in on the reason (or reasons) a couple is unable to get pregnant, a doctor may order tests for both partners.
Takeaway
Since thyroid issues are so common in women, testing for thyroid disease is often a standard part of infertility testing. These tests usually aren't routine for men unless there's a reason to suspect a thyroid issue, such as symptoms of thyroid disease.
There are many types of thyroid blood tests:
TSH test: Thyroid-stimulating hormone (TSH) is produced by the pituitary gland to regulate levels of thyroid hormone in the blood. Low levels can mean there's too much thyroid hormone; high levels can mean there's too little.
Free T4 test: Thyroxine (T4) is the main hormone produced by the thyroid, though it is largely inactive. Free thyroxine refers to the amount of thyroxine that's available to be converted to T3, which is active and able enter the target tissues when needed.
Free T3 test: Triiodothyronine (T3) is the other major thyroid hormone.
TPO test: Sometimes blood levels of thyroid peroxidase (TPO) antibodies will be measured to help diagnose autoimmune thyroid diseases—namely, Hashimoto's thyroiditis. This test can also be positive in patients with Grave's disease.
Treatment
Treating infertility caused by thyroid disease or in which a thyroid problem is a contributing factor is, for the most part, a matter of using medication to bring thyroid hormone levels within a normal range. For men, this may help improve sperm quality and quantity.
For women, normalizing thyroid hormone levels can help correct menstrual or ovarian problems that may be causing infertility. Ideal thyroid hormone levels are needed for conception to take place, for infertility treatments such as IVF to be successful, and for a pregnancy to remain viable.
Takeaway
According to studies, a TSH value of less than or equal to 2.5 mIU/L indicates healthy thyroid hormone levels for pregnancy.
Hypothryoidism
Treatment involves hormone replacement therapy. The medication most often prescribed is levothyroxine—a synthetic form of T4 available under several brand names including Synthroid, Levothroid, Levoxyl, and Tirosint.
Sometimes synthetic triiodothyronine is included in treatment for thyroid disease, but this is not recommended during pregnancy because T3 does not cross the placenta.
Hyperthryoidism
Medicines called thionamides are commonly used to treat hyperthyroidism. These drugs work by causing the thyroid to make less thyroid hormones.
Typically, Tapazole (methimazole) is the preferred antithyroid medication for treating hyperthyroidism, but this drug is associated with birth defects when taken during the first trimester of pregnancy.
The alternative, propylthiouracil, is usually the preferred antithyroid medication for women who have hyperthyroidism of Graves' disease and are trying to conceive. However, it can cause severe liver damage in adults and children, so talk with your healthcare provider about the treatment options that are best for your individual needs.
Coping
There's no doubt that infertility is one of the most challenging medical problems an individual or a couple faces. Even when the cause or causes of infertility are discovered, the stress and continued uncertainty can be difficult for those wishing to have a child.
That said, if thyroid disease is involved in infertility, it usually can be successfully treated with medication to get thyroid levels back within a normal range. During this time, it's important for both partners to be open and supportive of one another during treatment. Once thyroid levels are normalized, the chances of conception should improve provided both partners are otherwise healthy.
Summary
A thyroid disorder can be one cause of infertility in males and females. A healthcare provider may order tests for both partners to determine whether thyroid abnormalities are contributing to infertility. Once treatment is started and thyroid function is managed successfully, most couples are able to move forward with family planning.
