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The thyrotropin in hydatidiform moles is human chorionic gonadotropin
The Journal of Clinical Endocrinology and Metabolism
|March 1, 1975
Summary
Human chorionic gonadotropin (hCG) possesses intrinsic thyrotropic activity, potentially causing hyperthyroidism in conditions like hydatidiform mole with elevated hCG levels. This study quantifies the thyrotropic activity of hCG.
Area of Science:
- Endocrinology
- Reproductive Biology
- Molecular Endocrinology
Background:
- Thyrotropic activity, measured as thyroid-stimulating hormone (TSH), has been observed to correlate with human chorionic gonadotropin (hCG) activity.
- This correlation has been noted in serum and tissue samples from patients with hydatidiform mole, a condition characterized by elevated hCG levels.
Purpose of the Study:
- To investigate and quantify the thyrotropic activity of human chorionic gonadotropin (hCG).
- To determine if hCG possesses intrinsic thyrotropic properties and its potential contribution to thyroid dysfunction in specific clinical conditions.
Main Methods:
- Correlation of TSH and hCG activity in serum and tissue samples from hydatidiform mole patients using McKenzie mouse bioassay and radioimmunoassay.
- Extraction and purification of hCG from molar tissue and urinary preparations using gel chromatography, affinity chromatography, and isoelectrofocusing.
- Assay of purified hCG preparations for both thyrotropic and hCG activities to determine activity ratios.
Main Results:
- A consistent ratio of thyrotropic activity to hCG activity (approximately 0.42-0.51 mμU TSH/U hCG) was observed in serum and purified molar hCG.
- Thyroid-stimulating activity was undetectable when hCG levels fell below 150-175 U/ml.
- Purified hCG preparations exhibited intrinsic thyrotropic activity, with molecular calculations suggesting hCG has approximately 1/4000 the thyrotropic activity of pituitary TSH.
Conclusions:
- Human chorionic gonadotropin (hCG) possesses intrinsic thyrotropic activity.
- The thyrotropic activity of hCG can be significant enough to cause hyperthyroidism in conditions with markedly elevated hCG levels, such as hydatidiform mole.
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