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Both hyper- and hypothyroidism may result in menstrual abnormalities. In the first,
amenorrhoea was described as early as 1840 by von Basedow. Nowadays, menstrual
disturbances are less common that in previous series. In a recent study, we found
that only 21.5% of 214 thyrotoxic patients had some kind of menstrual disturbances
in their cycle, compared to 50-60% in some older series. The more common manifestations
are hypo- and oligomenorrhoea. Moreover, hyperthyroidism in women has been linked to
reduced fertility, although most thyrotoxic women remain ovulatory according to results
of endometrial biopsies.
In hypothyroidism, the frequency of menstrual irregularities has been reported very recently to be 23.4% among 171 hypothyroid patients studied. This is far more less in comparison with previous studies, which showed that 50-70% of hypothyroid female patients had menstrual abnormalities. Moreover, the most common manifestation is oligomenorrhoea. One most likely explanation for this discrepancy should be that thyroid disease is diagnosed earlier than it once was, and so the clinical picture is generally milder. However, genetical differences among the different groups studied cannot be excluded. These new data are inconsistent with what is generally believed or written in the classic thyroid textbooks, concerning the frequency and pattern of menstrual disturbances in hyper- and hypothyrodism and indicated that such opinions should be revised. Hyperthyroidism in women has been linked to reduced fertility, although most thyrotoxic women remain ovulatory according to results of endometrial biopsies. Severe hypothyroidism is commonly associated with failure of ovulation. Ovulation and conception can occur in mild hypothyroidism. However, these pregnancies are often associated with abortions, stillbirths, or prematurity. Subclinical hypothyroidism may be of greater clinical importance in infertile women with "unexplained" infertility, especially when the luteal phase is inadequate and such patients should be investigated in depth for thyroid dysfunction. |
