Sex steroids and thyroid function tests: the role of estrogen and progestogen.

Abstract

Thyroid functions were evaluated in 102 14-47 year old women (mean age 28.3 years by comparing changes during administration of estrogen (.08 mg ethinyl estradiol; 1.25 mg Premarin) progestogen (4 mg chlormadinone acetate; 10 mg dydrogesterone) and a combination of estrogen and progestogen (1 mg norethindrone .05 mg mestranol; .5 mg ethynodiol diacetate 1 mg mestranol). Total thyroxine (T4) concentrations were significantly elevated in women receiving estrogen and estrogen-progestogen. Parallel increases of total triiodothyronine (T3) were observed in women in the estrogen groups except for those receiving conjugated estrogen. The use of estrogens resulted in decreased T3 resin uptake values and increased thyroxine-binding globulin (TBG) capacity levels thus showing the negative correlation between these determinations. In the ethinyl estradiol and mestranol-norethindrone groups the free thyroxine index (FTI) calculated by dividing the total T4 by the total TBG fell within normal ranges. No significant changes of total T4 total T3 T3 resin uptake TBG capacity and FTI values were noted in women taking progestogen. Serum levels of thyroid-stimulating hormone were normal in women taking estrogen and/or progestogen.(AUTHORS MODIFIED)