Early hypothyroidism in patients with menorrhagia.

The functional status of the thyroid gland was evaluated in 67 apparently euthyroid menorrhagic women by a thyrotropin-releasing hormone test. Fifteen of 67 showed mild primary hypothyroidism characterized by a small but significant elevation of basal levels of thyroid-stimulating hormone (5.9 +/- 0.76 versus 2.4 +/- 0.24 mU/L) and lowering of serum thyroxine levels (85 +/- 4.2 versus 105 +/- 3.0 nmol/L) to levels that were nevertheless within the normal range and exaggerated response of serum thyroid-stimulating hormone and thyroxine to administration of thyrotropin-releasing hormone. Triiodothyronine levels showed no significant change. The terms early and potential hypothyroidism appear to better describe the preliminary phases of hypothyroidism than do other terms in current use. Menorrhagia disappeared within 3 to 6 months and did not reappear in 1 to 3 years of follow up in all patients with early hypothyroidism to whom L-thyroxine was given. This was accompanied by a significant decline in random serum thyroid-stimulating hormone levels and rise of thyroxine levels to those found in the group with a negative response to the thyrotropin-releasing hormone test, with no change in levels of triiodothyronine. Further systematic study of thyroid function in menorrhagia is warranted.