Human chorionic gonadotropin stimulation of Leydig cell function in puberty. Comparison of testosterone response in plasma and urine.

The plasma and urinary testosterone response to one i.m. injection of 5,000 IU human chorionic gonadotropin (HCG) was tested in 45 children and adolescents of several diagnostic entities: testosterone was measured before the injection and on the second, fourth and sixth days thereafter. It was found that there was a better correlation between the testosterone concentrations and the different pubertal stages than between testosterone concentration and either chronological or skeletal age. In the children with normal pubertal development, there was a slight rise in basal testosterone concentration with the progression of the pubertal stages. HCG caused a rise in plasma and urinary testosterone: this response was more marked in pubertal stages 4 and 5. The urinary response was variable whereas the changes in plasma testosterone concentration were more constant. In children and adolescents with primary or secondary hypogonadism, the basal levels of testosterone were low or undetectable and there was only a slight response to the single dose of HCG. It was concluded that a single i.m. injection of 5,000 IU HCG and the determination of plasma testosterone before, and two and four days after injection is a useful screening test for Leydig cell function.