The effect of altering thyroid hormone concentrations on plasma gonadotrophins in postmenopausal women

Plasma gonadotrophin levels were measured at frequent intervals in six postmenopausal thyrotoxic women treated with carbimazole. All patients showed an increasing follicle stimulating hormone/luteinizing hormone (FSH/LH) ratio as the thyroid hormone concentrations fell to normal and then into the hypothyroid range. Although the increased FSH/LH ratio was primarily due to a rise of FSH, two patients had a rise of both gonadotrophins. It is suggested that menstrual irregularities occurring in premenopausal women with disorders of thyroid metabolism may be related to similar changes.