How thyroid hormones impact female fertility

Thyroid hormones interact with your reproductive hormones, estrogens and progesterone, to preserve normal function of the ovaries and maturation of the egg (oocyte).1 If your thyroid gland releases of too much (hyperthyroidism) or too little (hypothyroidism) thyroid hormones, the balance of reproductive hormones can be impaired5 with consecutive thyroid-related fertility problems such as ovulation disorders, irregular periods, and trouble getting pregnant or carrying a baby to term.8 Even though you may be having a regular menstrual period, you may not be ovulating. Since thyroid disease is a common endocrine disorder in women of childbearing age, the first thing to do when you have troubles getting pregnant is to have your thyroid checked, especially if thyroid disease runs in your family.

The overactive thyroid

Hyperthyroidism is ten times more common in women than inmen9 and can cause a woman to have difficulties in not only getting pregnant, but also staying pregnant. If your thyroid gland releases excessive amounts of thyroid hormones into the bloodstream, you are hyperthyroid. The most common reason for hyperthyroidism in young women is Graves’ disease, an autoimmune disorder where antibodies mistakenly attack the thyroid gland. This stimulates the gland to overproduce thyroid hormones.6 If you experience unhealthy weight loss, this can hamper your chances of falling pregnant, too.10

Key symptoms of hyperthyroidism6

  • Weakness
  • Irritability
  • Fast heart rate
  • Weight loss
  • Trembling hands
  • Prominent, staring eyes
  • Increased sensitivity to heat
  • Fast growing fingernails
  • Hair loss
  • Thin and smooth skin
  • Frequent bowel movement
  • Abnormal menstrual periods
  • Complete absence of your monthly cycle

Individually or in combination, these common symptoms of hyperthyroidism may be the cause of your fertility problems. If hyperthyroidism is at the root of your infertility, proper treatment with a resulting optimal TSH level (TSH: thyroid stimulating hormone, which brings your thyroid to produce thyroid hormones) usually corrects the disturbance. If you are at the right TSH level but still have problems getting pregnant, you may need to consult with an endocrinologist who specializes in reproductive disorders. See also www.fertility.com

The underactive thyroid

When you have a family history of thyroid disease or any autoimmune disease you have an increased risk for hypothyroidism.11 If your thyroid gland produces too little thyroid hormones, TSH will increase to stimulate your thyroid gland to fill up the gap. Elevated TSH has been observed in 4.6% of cases of female infertility.12

Key symptoms of hypothyroidism7

  • Fatigue
  • Mental fogginess
  • Poor concentration an memory
  • Weight gain
  • Increased sensitivity to cold
  • Muscle or joint pain
  • Dry skin and hair
  • Brittle nails
  • Abnormal periods

If you were hypothyroid you could have infrequent and light menstrual bleeding, no menstrual cycles or irregular cycles due to problems with ovulation. These menstrual irregularities are approximately three times more common in hypothyroid women than in women with normal thyroid function.5 With a low-functioning thyroid, levels of prolactin, the hormone that stimulates breast milk production after delivery, may increase and inhibit ovulation.5 Hypothyroidism is also associated with an increased risk of polycystic ovarian disease (PCOS), a condition that causes cysts on the ovaries and inhibits pregnancy.13

References

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  • Stuttgart 2009; 33-38.
  • 2- American Thyroid Association. General Information (2012) http://www.thyroid.org/thyroid-eventseducation-media/about-hypothyroidism Accessed October 2012.
  • 3- Healy DL, Trounson AO, Andersen AN. Female infertility: causes and treatment. Lancet 1994; 343:1539–1544.
  • 4- Meikle AW. The interrelationship between thyroid dysfunction and hypogonadism in men and boys. Thyroid 2004; 14 (Suppl 1): S17-S25.
  • 5- Krassas GE, Poppe K, Glinoer D (2010) Thyroid function and human reproductive health. Endocr.Rev. 2010 31:702-755.
  • 6- The American Thyroid Association (2012) Hyperthyroidism http://www.thyroid.org/what-is-hyperthyroidism/Accessed October 2012.
  • 7- The American Thyroid Association (2012) Hypothyroidism Brochure. http://www.thyroid.org/whatis-hypothyroidism Accessed October 2012.
  • 8- Bercovici JP. Menstrual irregularities and thyroid diseases. Feuillets de biologie 2000; 74: 1063-1070.
  • 9- Vanderpump MPJ, Tunbridge WMG, French JM et al. The incidence of thyroid disorders in the community: A twenty-year follow-up of the Whickham Survey. Clin
  • Endocrinol 1995; 43: 55-69.
  • 10- Green BB, Weiss NS, Daling JR. Risk of ovulatory infertility in relation to body weight. Fertility and Sterility 1988; 50 (5): 721-726.
  • 11- The Hormone Foundation’s Patient Guide to the Management of Maternal Hypothyroidism Before, During, and After Pregnancy. De Groot LJ, Stagnaro-Green A,
  • Vigersky R, The Hormone Foundation 2007 http://www.hormone.org/Resources/Patient_Guides/upload/mgmt-maternal-hypothyroidism-070609-2.pdf.
  • Accessed October 2012.
  • 12- Grassi G, Balsamo A, Ansaldi C et al. Thyroid autoimmunity and infertility. Gynecol Endocrinol 2001; 15: 389–396.
  • 13- Beyond Infertility. Polycystic Ovary Syndrome (PCOS). U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES. National Institutes of Health; Eunice Kennedy
  • Shriver National Institute of Child Health and Human Development 2008 http://www.nichd.nih.gov/publications/pubs/upload/PCOS_booklet.pdf.
  • Accessed October 2012.
  • 14- De Groot L, Abalovich M, Alexander EK, Amino N, Barbour L et al. Management of Thyroid Dysfunction during Pregnancy and Postpartum: An Endocrine Society
  • Clinical Practice Guideline. J Clin Endocrinol Metab 2012; 97 (8): 2543-2565.