Hypothyroidism can impair a woman's fertility or ability to carry a pregnancy to term.
Ten to 15 percent of U.S. women have fertility problems during any given year, according to the National Survey of Family Growth, and about 50 percent of women between the ages of 25 and 45 experience at least one episode of infertility. While there are numerous reasons a couple may fail to conceive, failure of ovulation is the most common cause of impaired fertility in women. Thyroid disease, particularly low thyroid hormone levels due to hypothyroidism, can interfere with ovulation.
Importance of Thyroid Hormones
Your thyroid gland, which is in your neck, just beneath your Adam's apple, secretes several hormones. Two of these -- triiodothyronine and thyroxine -- are essential for proper utilization of energy, protein production, growth, brain development and a number of other important functions. Thyroid hormones also regulate how your cells respond to other hormones, such as insulin. If your thyroid hormone levels are low, many processes in your body are adversely affected, including reproductive health in men and women.
Complex Hormonal Relationships
In most cases, hypothyroidism is caused by your thyroid gland's inability to manufacture and release enough thyroxine and triiodothyronine. As thyroid hormone levels fall, your hypothalamus and pituitary gland increase their production of thyroid releasing hormone and thyroid stimulating hormone. TRH and TSH would normally stimulate your thyroid hormone to work harder, but if your thyroid is incapable of responding, your blood levels of TRH and TSH keep rising. As TRH increases, it also stimulates production of another pituitary hormone called prolactin. High prolactin levels, in turn, may interfere with ovulation.
Impaired Ovulation and Implantation
According to a 2012 review in вЂњFrontiers in Endocrinology,вЂќ cellular receptors capable of responding to TSH and thyroid hormones are found in your ovaries and the lining of your uterus. In concert with hormones from your pituitary gland, thyroid hormones encourage the development of a mature ovum, or egg, during each menstrual cycle. If your egg is fertilized, a proper balance among TSH, thyroxine and triiodothyronine is then necessary for maintaining your pregnancy. So, hypothyroidism can interfere with your ability to ovulate, conceive or carry a pregnancy to term.
Even mild hypothyroidism can interfere with fertility in some women, according to the authors of a study published in the April 2003 issue of вЂњHuman Reproduction.вЂќ Treatment of hypothyroidism in these women may improve their chances for conceiving. Not all women who are hypothyroid are infertile, and many hypothyroid women do conceive. If hypothyroidism during pregnancy is not addressed, fetal brain development can be impaired and infants may suffer lifelong learning disabilities. In addition, maternal hypothyroidism can lead to low birth weight, premature birth and breathing problems in newborns.
Women who are trying unsuccessfully to conceive should ask their doctors if hypothyroidism might be playing a role. Screening for hypothyroidism is recommended for all pregnant women and is usually done during your first prenatal visit. Hypothyroidism is readily treated with a daily oral dose of thyroid hormone.