Menorrhagia and hypothyroidism

Editor—Prentice in his review of menorrhagia states that there is little evidence to link hypothyroidism with excessive menstrual loss.¹ He supports this with reference to a retrospective analysis of the records of 50 patients with myxoedema.² In this cohort 28 women (56%) complained of menstrual disturbance, with the most common complaint being menorrhagia (occurring in 18 (36%) of the women). The acid test of causation is, however, whether treatment of the condition corrects the menstrual dysfunction. In this study (which reported the women's perceived loss) and more recent studies in which the menstrual loss was measured³ treatment of hypothyroidism with thyroxine decreased menstrual blood loss.

Hypothyroidism may be greatly underdiagnosed as a cause of menorrhagia. Wilansky tested for thyrotrophin releasing hormone in 67 women with menorrhagia who had normal concentrations of thyroxine and thyroid stimulating hormone.⁴ Fifteen (22%) had abnormal tests and were treated with thyroxine. Twenty four of the total cohort (who had not had surgery and remained without a definitive diagnosis) were followed up one to three years later. Of these, eight had been treated with thyroxine for an abnormal test result for thyrotrophin releasing hormone, and all considered their menstrual loss to have returned to normal. Of the remaining 16 (whose test results were normal) nine (56%) still complained of menorrhagia. These findings were later replicated in a study of women who had menorrhagia associated with intrauterine contraceptive devices.⁵

All the available evidence supports a causative association between hypothyroidism and excessive menstrual loss. Some of the study methods are weak by modern standards, but in the absence of evidence to the contrary the conclusion must be that hypothyroidism is a correctable cause of menorrhagia. Prentice asserts that routine thyroid function tests are of no value in the investigation of women with menorrhagia. Maybe we are just conducting the wrong test of thyroid function, however, and all women with unexplained menorrhagia should be tested for thyrotrophin releasing hormone.