[Longitudinal study about the function of pituitary-thyroid axis in pregnancy].
OBJECTIVE
To evaluate the change about the function of pituitary-thyroid axis and the role of human chorionic gonadotropin (hCG) on regulation of pituitary-thyroid axis in pregnancy.


METHODS
The study was designed to provide longitudinal information of parameters of thyroid function and hCG in 74 healthy women during pregnancy and after delivery. Serum free triiodothyronine (FT3), free thyroxin (FT4), TT3, TT4, hCG and thyroid hormone binding globulin (TBG) concentrations were measured with radioimmunoassary and serum TSH concentration with immunoradiometric assay.


RESULTS
(1) The FT3 and FT4 values below the reference range were 5.88% and 9.80%, respectively, in third trimester and after delivery, both were 38.10%. The serum TSH level below the reference range was 31.25% in first trimester and supranormal were 11.90% after delivery. The serum hCG level at all stages of pregnancy was higher than postpartum. (2) The serum FT3 level was significantly higher in first (4.37 +/- 0.78) pmol/L and second (4.75 +/- 0.90) pmol/L trimesters than postpartum (2.96 +/- 0.84) pmol/L, decreased in third trimester (3.94 +/- 0.75) pmol/L and the lowest level after delivery. The serum FT4 level was significantly higher in first (14.07 +/- 1.44) poml/L and second (12.86 +/- 0.84) pmol/L trimesters than postpartum (10.45 +/- 1.45) poml/L, decreased in third trimester (11.29 +/- 1.00) pmol/L and the lowest level after delivery. (3) The serum TSH level was the lowest values in early pregnancy (0.88 +/- 0.83) mU/L, showed significant increase in second (1.86 +/- 1.04) mU/L and third (1.48 +/- 0.90) mU/L trimesters and reached maximal level after delivery (2.82 +/- 1.42) mU/L. (4) The serum hCG level was the highest in early pregnancy (309.05 +/- 320.02) micrograms/L, then significant decreased in second (69.11 +/- 19.18) micrograms/L and third (86.25 +/- 44.60) micrograms/L trimesters and was the lowest levels after delivery (29.92 +/- 20.91) micrograms/L. (5) A significant negative correlation between TSH and hCG levels and a significant positive correlation between hCG and FT4 and TT4/TBG were demonstrated.


CONCLUSIONS
(1) hCG may be as role on regulation of pituitary-thyroid axis during pregnancy and during certain time of postpartum. (2) After delivery, part of women were transient hypothyroxinemia.
Ye
X
X
Department of Endocrinology, People's Hospital of Guizhou Province, Guiyang 550002, China.
Shi
L
L
Huang
H
H
D000328:Adult; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D010902:Pituitary Gland / Q000502:physiology*; D011247:Pregnancy / Q000502:physiology*; D013961:Thyroid Gland / Q000502:physiology*