THYROID-HORMONE PROFILE IN NORMAL-PREGNAN CY

The aim of this study was to update the thyroid hormone profile in nor mal pregnant women with adequate iodine nutrition, to analyze the phys iological changes that occur during pregnancy and to know the role tha t TBG and bHCG exert on these changes. One hundred six pregnant women without goiter, former thyroid diseases or positive antimicrosomal ant ibodies were studied. Fifty three of them were prospectively followed during the gestational period. Thirty age matched non pregnant women w ere studied as a control group. Serum T3t, T4t, T41, conventional and IRMA TSH, rT3, TBG, bHCG, antimicrosomal antibodies and urinary iodine content were measured. Median urinary iodine content was 18.9 ug/ml i n pregnant women, discarding iodine deficiency, the main observed chan ges occurred between weeks 6 and 14 with significant elevations of T3t , T4t, T41, rT3, TBG and bHCG and TSH decrease. There was a positive c orrelation between TBG and T3t and T4t indicating a causal relationshi p. There was a negative correlation between T41 and TSH and between TS H and bHCG and a positive correlation between T41 and bHCG, suggesting a thyroid stimulator effect of bHCG which would raise T41 and thus in hibit TSH secretion.