Human chorionic gonadotrophin (HCG) stimulation test and testosterone response in children with micropenis

Human chorionic gonadotropin (HCG) stimulation test is a reliable dynamic test for the evaluation of testicular function during childhood. A single dose of HCG injection at dose of 100 iu/kg is able to produce a progressive but modest rise in testosterone level for 72 to 120 hours in presence of a viable testicular Leydig cells.

To describe pattern of testicular response to HCG stimulation in prepubertal children with micropenis seen at a paediatric endocrinology training centre.

A retrospective review of all children seen over a fifteen months period and evaluated for micropenis using single dose HCG stimulation protocol. Information was retrieved from the clinic register and case notes of patients. Information retrieved includes age, anthropometry, associated clinical finding and results of stimulation test. Interpretation of test was as sited by Knorr and colleagues.

Six children with micropenis had HCG stimulation test. Mean age of children was 49.9 months age range 2 months to 84 months. Base line testosterone level ranged from 0 ng/ml to 0.35 ng/ml with a mean of 0.3 ng/ml. The mean testosterone level after HCG stimulation was 1.26 ng/ml and range between 0.35 and 3.2 ng/ml. Three subjects had normal increase in testosterone level post stimulation. There was no significant increase in mean stretched penile length of 0.4 cm.

HCG stimulation is an important test to determine Leydig cell function and testosterone secretion in children with micropenis. 3 (50%) including a cryptochid child showed normal rise in testosterone level post HCG stimulation. The normal response indicates a normal leydig cell function and possible presence of viable testicular tissues in the cryptochid.