Maternal thyroid hormones and outcome of pre-eclamptic pregnancies

Plasma concentrations of total and free thyroxine (TT4 and FT4), total and free triiodothyronine (TT3 and FT3), thyroid-stimulating hormone (TSH), plasma albumin and urate were measured in 39 proteinuric pre-eclamptic patients presenting before labour. Pre-eclamptic patients had significantly lower FT4 and higher TSH concentrations compared with values in third trimester normotensive pregnancies. There was a significantly higher frequency of lower TT4, TT3 and high TSH levels in the subgroup of pre-eclamptic patients who had low-birthweight babies. Thyroid hormone concentrations were not correlated with gestation at delivery or birthweight but, with the exception of FT4, were correlated with plasma albumin and urate concentrations. Plasma TSH correlated with birthweight and with plasma urate. The results suggest that mild biochemical hypothyroidism may be found in proteinuric pre-eclampsia, and the concentrations of TT4, TT3, FT3 and TSH may reflect the severity of pre-eclampsia.