The Use of an Enzyme-Amplified Immunoassay for TSH in the Assessment of Thyroid Function in Pregnant and Postpartum Women

The apparent clinically euthyroid status of a group of 56 pregnant women has been found to correlate better with the values obtained from a highly sensitive enzyme-amplified immunometric assay for thyroid-stimulating hormone (TSH) than with values obtained for TT4, TT3, or FT4. The parameters were measured on four occasions during normal pregnancy and in early postpartum. The mean serum TSH values obtained at any stage of pregnancy studied were not significantly different than values obtained in nonpregnant controls. In contrast, serum TT3 and TT4 increased with pregnancy, while the values obtained for FT4 decreased markedly during gestation. In the early postpartum while serum TT3 and TT4 remained elevated, the TSH level decreased significantly despite an apparent fall in FT4. These data support the use of sensitive TSH measurements in preference to FT4 estimation as a test of thyroid function in pregnant and postpartum women.