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Does human chorionic gonadotropin have human thyrotropic activity in vivo?
R A Foulk1, T J Musci, E D Schriock
1Reproductive Endocrinology Center, University of California, San Francisco 94143-0556, USA.
Summary
Endogenous human chorionic gonadotropin (hCG) during pregnancy stimulates thyroid function. However, exogenous hCG used in ovarian hyperstimulation does not impact the hypothalamic-pituitary-thyroid axis.
Area of Science:
- Reproductive Endocrinology
- Thyroid Physiology
Background:
- Thyroid cells exhibit sensitivity to human chorionic gonadotropin (hCG).
- Thyroid hormones play a role in reproductive functions, including ovarian and endometrial physiology.
Purpose of the Study:
- To investigate the in vivo effects of endogenous and exogenous hCG on thyroid function.
- To differentiate the impact of hCG during normal pregnancy versus controlled ovarian hyperstimulation (COH).
Main Methods:
- Correlational analysis of circulating hCG with serum free thyroxine and thyrotropin levels in pregnant women.
- Assessment of thyroid function (free thyroxine and thyrotropin) in non-pregnant patients undergoing COH with exogenous hCG administration.
Main Results:
- In normal pregnancy, endogenous hCG concentrations positively correlated with free thyroxine and negatively with thyrotropin.
- Exogenous hCG administration during COH resulted in lower hCG levels than pregnancy and did not alter thyroid function parameters.
- p-values for COH group were > 0.22, indicating no statistically significant effect.
Conclusions:
- Endogenous hCG isoforms during early pregnancy possess in vivo thyrotropic activity.
- Exogenous hCG, under clinical COH conditions for assisted reproduction, does not influence the hypothalamic-pituitary-thyroid axis.