Thyroid profile in normal pregnancy
Wohllk, N.; Osorio, M.; Aguayo, J.; Pineda, G.; Miranda, V.; Norambuena, H.
Revista Medica de Chile 121(6): 652-659
1993
ISSN/ISBN: 0034-9887 PMID: 8278701 Document Number: 415912
The aim of this study was to update the thyroid hormone profile in normal pregnant women with adequate iodine nutrition, to analyze the physiological changes that occur during pregnancy and to know the role that TBG and bHCG exert on these changes. One hundred six pregnant women without goiter, former thyroid diseases or positive antimicrosomal antibodies were studied. Fifty three of them were prospectively followed during the gestational period. Thirty age matched non pregnant women were 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 in pregnant women, discarding iodine deficiency, the main observed changes occurred between weeks 6 and 14 with significant elevations of T3t, T4t, T41, rT3, TBG and bHCG and TSH decrease. There was a positive correlation between TBG and T3t and T4t indicating a causal relationship. There was a negative correlation between T41 and TSH and between TSH and bHCG and a positive correlation between T41 and bHCG, suggesting a thyroid stimulator effect of bHCG which would raise T41 and thus inhibit TSH secretion.