[Effect of estrogen upon thyroid metabolism (author's transl)]

During enhanced endogen estrogen production (pregnancy) as well as during exogen estrogen application a rise occurs in TBG concentration in serum, which seems to be dose related. Simultaneously with the TBG there is an increase in total T4 and T3; the concentrations of the free T4 and T3 however decrease. Towards the end of pregnancy AFT4 is significantly decreased, compared to the controls, AFT3 being in the lower normal range. The lower concentrations of the free hormones are also documented by a decline in the T4/TBG and T3/TBG ratios. Normal basal TSH concentration in serum suggest a metabolic state which is still compensated. Oral contraceptives with low estrogen content have no influence on TBG, T4 and T3 concentrations.