Plasma estrogens in euthyroid and thyrotoxic women

Plasma levels of estrogen were measured daily by radioimmunoassay for 28 consecutive days in 12 healthy euthyroid women and 15 thyrotoxic women (10 with hypomenorrhea and 5 with amenorrhea) before commencement of therapy (except in one case) in an effort to increase understanding of the relationship between the thyroid gland and ovarian function. The results show that the patterns of plasma estrogen in thyrotoxic women with hypomenorrhea were similar to those in euthyroid women, although the levels in the thyrotoxic women were significantly elevated (P less than 0.001). Thyrotoxic women with amenorrhea also had a markedly elevated plasma estrogen level with a persistence of a sharp peak of estrogen but without the secondary estrogen rise associated with corpus luteum function. This suggests a failure of the positive feedback effect of estrogen on the hypothalamopituitary axis with resultant failure of ovulation.