Thyroid disease and female reproduction

Objective: To review the menstrual function and fertility in thyroid diseas e, mainly in hyperthyroidism and hypothyroidism. Also to register the conse quences of I-131 therapy, which is used widely in the treatment of Graves' disease and thyroid cancer, on subsequent pregnancies and on fertility in t hese patients. Design: A MEDLINE computer search was used to identify relevant studies. Th e type of menstrual disturbances and the status of fertility were recorded from all the studies found. Also, the fertility and genetic hazard of femal e patients with Graves' disease and thyroid cancer who were treated with I- 131 were registered. Result(s): Both hyperthyroidism and hypothyroidism may result in menstrual disturbances. Menstrual abnormalities are less common now than in previous series. In a recent study, we found that only 21.5% of 214 thyrotoxic patie nts had some type of menstrual disturbance, compared to 50 to 60% in some o lder series. The most common manifestations are hypomenorrhea and oligomeno rrhea. According to the results of endometrial biopsies, most thyrotoxic wo men remain ovulatory. Moreover, the genetic hazard incident to radioiodine therapy in Graves' disease and thyroid carcinoma is very small; exposure to I-131 does not cause reduced fecundity, and the risk of loss of fertility is not a contraindication for its use in these patients. In hypothyroidism, the frequency of menstrual irregularities has very recen tly been reported to be 23.4% among 171 hypothyroid patients studied. This is much less than that reported in previous studies, which showed that 50 t o 70% of hypothyroid female patients had menstrual abnormalities. The most common manifestation is oligomenorrhea. Severe hypothyroidism is commonly a ssociated with failure of ovulation. Ovulation and conception can occur in mild hypothyroidism. These pregnancies are, however, often associated with abortions, stillbirths, or prematurity. The latter may be of greater clinic al importance in infertile women with unexplained infertility. Conclusion(s): These new data, mainly concerning menstrual abnormalities in hyperthyroidism and hypothyroidism, are inconsistent with what is generall y believed and written in the classic thyroid textbooks and indicate that s uch opinions should be revised. (Fertil Steril(R) 2000;74:1063-70. (C) 2000 by American Society for Reproductive Medicine).