Disturbances of menstruation in hypothyroidism

OBJECTIVES Most thyroid textbooks describe hypothyroidism resulting in chan ges in the length of the menstrual cycle and in the amount of bleeding. Our experience at a busy thyroid clinic had given a picture which differs from that presented in the literature. The aim of this study was to determine t he frequency and type of menstrual irregularities in premenopausal hypothyr oid patients. DESIGN AND PATIENTS We investigated the menstrual history, starting 6 month s before the discovery of the disease, in 171 female premenopausal hypothyr oid patients and 214 normal controls, with similar age and body mass index (BMI), MEASUREMENTS TSH, TT4, TT3 and thyroid antibodies were measured by radioimm unoassay, while BMI was calculated from the ratio of body weight in kg to h eight in m(2) RESULTS Of the 171 hypothyroid patients, 131 (76.6%) had regular cycles and 40 (23.4%) irregular periods. Oligomenorrhoea and menorrhagia were the mos t common features in the latter group. No difference in BMI was found betwe en the patients with or without menstrual abnormalities, or between patient s and controls. TSH, TT4 and TT3 levels did not differ between patients wit h normal and abnormal menstruation. Forty-six (26.9%) out of 171 patients h ad subclinical hypothyroidism (group A), 42 (24.6%) mild hypothyroidism (gr oup B) and 83 (48.5%) severe hypothyroidism (group C), Thirty-seven from gr oup A (80.4%), 32 from group B (76.2%) and 62 from group C (74.7%) had norm al periods. These differences were not statistically significant. Eighty-ei ght (88.9%) out of 99 patients in whom thyroid antibodies were measured had positive titres, Nineteen (21.6%) of the patients with positive thyroid an tibodies had menstrual irregularities. This percentage did not differ from that found in the whole group of patients (23.4%), Out of 214 normal contro ls, 196 (91.6%) had normal menstruation and 19 (8.4%) irregular cycles. The latter group included mainly women with oligomenorrhoea. CONCLUSIONS These data demonstrate that hypothyroidism in women is less fre quently associated with menstrual disturbance than was previously described . Also, menstrual irregularities tend to be more frequent in sever hypothyr oidism in comparison with mild cases, although this finding was not statist ically significant. Oligomenorrhoea and menorrhagia are the most common men strual disturbances.