Infertility and Thyroid Disease

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Given the extensive role the thyroid plays in the overall function of the body, it's not surprising that a problem with this gland in either hopeful parent could lie behind the monthly disappointment of a negative pregnancy test. Fortunately, when a thyroid disorder is discovered to be a cause of infertility, and once it's being managed successfully, most couples are able to move forward with their plans to begin a family.

how thyroid disease can affect your cycle
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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 infrequent menstruation, or oligomenorrhea, in which periods are more than 35 days apart. By contrast, an overactive thyroid or an excess of thyroid hormone in blood (thyrotoxicosis) are associated with both 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.
  • Shortened luteal phase: This is the period of time between ovulation and menstruation. When it's 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.

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 with 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 swim), sperm morphology (the shape of sperm), and semen volume (the amount of ejaculate a man produces). Hyperthyroidism has been shown to affect sperm quantity and quality as well. This is important because, according to the American Urological Association (AUA), if a male infertility factor is diagnosed in a couple who's having trouble getting pregnant, it's almost always due to a problem with the sperm.

In men, thyroid disease—particularly hyperthyroidism—also has been found to affect sexual function in a variety of ways, including decreased libido, erectile dysfunction, and premature ejaculation. Of course, none of these conditions renders a man infertile, but they can certainly make it difficult for a couple to follow through on attempts to get pregnant naturally.


Infertility is diagnosed in a couple who have unsuccessfully been trying to get pregnant for a year by having unprotected intercourse. This is the point at which most are advised to see a fertility specialist (typically a reproductive endocrinologist; men with fertility issues also may consult a urologist). Because female fertility drops dramatically with age, women who are 35 or over typically are advised to see a 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 will order a battery of tests for both partners.

Since thyroid issues are so common in women, testing for thyroid disease often is a standard part of their infertility workups. These tests usually aren't routine for men unless there's a reason to suspect a thyroid issue, such as symptoms of thyroid disease.

Regardless, if thyroid testing is done on either partner, it simply will involve evaluating a sample of blood. There are many types of thyroid blood tests, but the ones most often done include:

  • TSH test: TSH stands for "thyroid stimulating hormone," a hormone that's 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: T4, or thyroxine, is the main hormone produced by the thyroid. "Free" refers to the amount thyroxine that's available to enter the bloodstream when needed.
  • Free T3 test: T3, or triiodothyronine, is the other major thyroid hormone.
  • TPO test: Sometimes blood levels of thyroid peroxidase antibodies will be measured to help diagnose autoimmune thyroid diseases—namely, Grave's disease and Hashimoto's thyroiditis.

Thyroid Disease Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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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 hormone levels can help to correct menstrual or ovarian problems that may be causing infertility. Ideal thyroid hormone levels also are necessary for conception to take place, for infertility treatments such as IVF to be successful, and for a new pregnancy to remain viable.

According to studies, a TSH value of less than or equal to 2.5 mIU/L indicates healthy thyroid hormone levels for pregnancy.

In the case of hypothyroidism, this means hormone replacement therapy. The medication most often prescribed is levothyroxine—a synthetic form of T3 available under several brand names including Synthroid, Levothroid, Levoxyl, and Tirosint. Sometimes synthetic triiodothyronine is included in treatment for thyroid disease, but this is unusual.

Treatment for hyperthyroidism is an antithyroid drug, which works by causing the thyroid to make less hormone. Typically, Tapazole (methimazole) is the preferred antithyroid medication for treating hyperthyroidism; however, this drug is associated with birth defects when taken during the first trimester of pregnancy. At the same time, the alternative, propylthiouracil, can cause severe liver damage in adults and children. However, it's usually the preferred antithyroid medication for women who have hyperthyroidism of Graves' disease and are trying to conceive.


There's no doubt that infertility is one of the most challenging medical problems an individual or a couple faces. This is especially true when it's unclear why conception isn't happening, technically known as unexplained infertility. Even when the cause or causes of infertility are discovered, the stress and continued uncertainty can be overwhelming for those wishing to have a child.

That said, when it turns out that thyroid disease is involved in infertility it should be heartening to know that, whether the man or woman is affected, it generally can be successfully dealt with via 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 be greatly increased provided both partners are otherwise healthy.

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