METABOLISM OF EXOGENOUS HUMAN CHORIONIC GONADOTROPHIN IN MEN

Abstract

The immunoreactivity of a commercial preparation of human chorionic gonadotrophin (HCG) was determined in a homologous double antibody radioimmunoassay for HCG using antisera to the β-subunit of the hormone. The immunoreactivity of the commercial HCG was found to be 2·2 ± 0·3 (mean ± 2 s.d.) times the biological potency. Exclusion chromatography of the commercial HCG and then curve resolution of the elution profile derived from the radioimmunoassay revealed that on a molar basis, 21% of the immunoreactivity was attributable to β-HCG. The rate of clearance of this preparation of HCG from the plasma after intravenous administration was determined as a function of the dose administered to ten normal men (age 36–64 years). The doses ranged from 10 000 to 300 000 i.u. immunological potency. The rate of clearance decreased significantly (r = 0·574, P< 0·05) with increasing doses of HCG from a mean of 786 ml/h at the lowest dose to a mean of 298 ml/h at the highest dose. The renal clearance of administered HCG also decreased with increasing doses; the mean renal clearance of the 10 000 i.u. dose was 3·6 times the mean renal clearance after administration of 200 000 i.u. When the accumulated urinary HCG was expressed as a percentage of the dose administered, 14·1% of the 10 000 i.u. dose and 9·8% of the higher doses accumulated in the urine, suggesting that non-renal clearance increased with increasing dose.