Evidence supports association between hypothyroidism and menorrhagia

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.

Author's reply

EDITOR—It is interesting how different people interpret the published literature. Weeks, in responding to my article, believes that the literature supports the concept that hypothyroidism is a significant cause of menorrhagia and consequently we should be assessing thyroid function in all women. This view is at odds with the guidance from the Royal College of Obstetricians and Gynaecologists. The advice given in the college's Evidence Based Clinical Guidelines, where the same evidence was considered, is that thyroid function tests do not need to be routinely performed in the evaluation of menorrhagia.1 The reasons given were that in the studies examined menstrual blood loss was not objectively measured and the diagnosis of hypothyroidism relied on a test for thyrotrophin releasing hormone in patients with normal concentrations of thyroid stimulating hormone and thyroxine.2 3

The only case report in which objective measurement was performed included only one subject, which is not the implication in Weeks's letter. Hypothyroidism is a common clinical condition, and women are affected six times more commonly than men. It would not be surprising if in a proportion of women with menorrhagia hypothyroidism, clinical or subclinical, coexisted. The routine screening for thyroid disease is not recommended in asymptomatic adults, 4 and the treatment of subclinical hypothyroidism is controversial.5 Weeks is advocating an expensive screening programme of unproved value. It is only reasonable routinely to test thyroid function in women with menorrhagia as part of a prospective study designed to address this specific question. Until that time we should follow national guidelines.2