Getting pregnant may be as simple as correcting underlying thyroid hormone imbalances, according to scientific results published in the May 2008 Nature journal "Clinical Practice Endocrinology & Metabolism." Restoring normal thyroid hormone levels can optimize fertility as abnormal levels of thyroid hormone affect sex-hormone-binding-globulin. This, in turn, regulates reproductive hormones.
Function
According to the MayoClinic.com, the thyroid gland is a small butterfly-shaped organ located in the front of the neck. It produces two types of thyroid hormone, T3 and T4. A gland in the brain called the hypothalamus produces thyrotrophin releasing hormone which stimulates the pituitary gland to produce thyroid stimulating hormone. The thyroid gland then releases thyroid hormones including T3 and T4.
Thyroid hormones regulate several major body functions including metabolism, cardiac function and reproduction. When the thyroid gland becomes diseased or cancerous, its production of thyroid hormones can be either suppressed or overactive. Abnormal thyroid hormone levels cause problems with reproductive hormones and fertility.
Causes
Reproductive hormones are disrupted by either over- or under-production of thyroid hormone and has multiple origins. According to MayoClinic.com, common causes of under-production include an autoimmune disease called Hashimoto's thyroiditis in which the body produces antibodies which destroy thyroid cells and decrease thyroid production. Cancer of the thyroid gland is treated by surgical removal of the gland which causes immediately causes the gland to become under-active unless treated by lifelong use of supplemental oral thyroid hormone. A possible side effect of radiation therapy to treat head and neck cancers is damage to the thyroid gland which also causes under-production. Another cause would be using medications such as lithium which are prescribed for psychiatric disorders.
Approximately one in 3,000 babies are born without a functional thyroid gland according to MayoClinic.com. Congenital hypothyroidism must be treated immediately to prevent cognitive developmental defects.
Auto-antibodies can also act to overstimulate the thyroid gland in Graves' disease. Benign thyroid nodules which secrete excess thyroid hormone in Plummer's disease and severe inflammation called thyroiditis also cause excessive thyroid hormone production.
Female Effects
Conditions that arise from dysfunction of the thyroid gland are due to either an over-production of thyroid hormone called hyperthyroidism or under-production of thyroid hormone called hypothyroidism. Either extreme can affect reproductive hormone balance and reproductive function.
According to the Columbia University Medical Center website, low levels of thyroid hormone can cause infertility in several ways. Hypothyroidism can prevent women from ovulating even if they have regular periods. Hypothyroidism can cause polycystic ovarian syndrome which results in the formation of multiple non-functional ovarian cysts instead of normal follicles on the ovary. Severe cases of hypothyroidism can cause abnormally high levels of another hormone, prolactin, which prevents ovulation.
Abnormal thyroid levels impair reproductive hormone levels and interfere with normal pregnancy. Pregnant women with abnormal thyroid levels should work closely with their doctor to monitor thyroid hormone levels to reduce the the risk of pregnancy complications, according to Dr. Roger W. Harms, M.D., Mayo Clinic obstetrician and medical editor-in-chief. Having too much thyroid hormone while pregnant can also cause fetal loss, premature labor or pregnancy complications.
Male Effects
Normal testicular development before birth, pre-puberty and during puberty requires normal levels of T3 hormone production. After puberty, abnormal thyroid hormone levels disrupt normal sperm production. Over-production of thyroid hormone affects the pituitary gland and indirectly affects testicular function by affecting the secretion of releasing hormones and increasing the normally low-level conversion of androgens to estrogens.
Prevention
According to the International Council on Infertility Information Dissemination, women who suspect they may have fertility problems should ask their reproductive endocrinologist to include testing for thyroid stimulating hormone, T3 and T4. If abnormally low levels are found, patients should be prescribed oral thyroid hormone replacement to normalize their thyroid levels before beginning fertility treatments.
According to MayoClinic.com, over-production of thyroid hormone can be treated by administering radioactive iodine or anti-thyroid medications to normalize thyroid levels.
