Decrease in serum sex hormone binding globulin during human chorionic gonadotrophin stimulation in prepubertal boys

Temporal relationships between steroidogenic and sex hormone binding globulin (SHBG) responses to hCG were studied in 27 prepubertal boys: 19 with incomplete testicular descent and 8 with hypogonadotrophic hypogonadism (HH). Nine of the boys with incomplete testicular descent were given a single im injection of hCG and blood samples were taken daily for 5 days. Six of them showed a slight decrease in SHBG concentration by day 5. All the other 18 boys were given four im injections of hCG on days 0, 4, 7 and 10. Blood was taken before each injection and on day 14. In the boys with incomplete testicular descent SHBG concentration decreased by day 14 (P less than 0.01). All the boys with HH had an impaired testosterone response to hCG, and SHBG levels did not decrease after hCG. In only 2 of these boys SHBG concentrations were greater than 10% below the basal by day 14. These boys, however, also had the highest testosterone responses of their group. Thus it appears that if testosterone increases in prepubertal boys, SHBG decreases.