THE USE OF THE HCG STIMULATION TEST IN THE ENDOCRINE EVALUATION OF CRYPTORCHIDISM

Objective To review retrospectively the value of the human chorionic g onadotrophin (hCG) test in the evaluation of prepubertal boys with bil ateral impalpable testes. Subjects and methods The study comprised 31 boy's investigated between 1974 and 1990 at the Hospital for Sick Chil dren, London. All boys had an hCG test consisting of three intramuscul ar injections of hCG on successive days at a daily dose dependent on t heir age (< 1 year old. 500 units; 1-10 years, 1000 units; > 10 years, 1500 units). Blood samples were taken before the first dose and 24 h after the last dose and the level of plasma testosterone assessed and expressed as a pre/post ratio, Results Eight boys had no response to h CG, due to anorchia. One boy had no response to hCG but had bilateral atrophic intra-abdominal testes. Twenty-two boys responded to hCG and had testes whose size was related to the degree of testosterone elevat ion after this stimulatory test, The hCG test therefore had a positive predictive value of 89%, and a negative predictive value of 100%, The re was a quantitative difference in testosterone response between 14 b oys who had bilateral intra-abdominal testes of 'normal' volume (media n pre/post ratio, 11.4) and nine boys who had an otherwise reduced vol ume of testes (dysplastic or unilateral intra-abdominal) (median pre/p ost ratio of 4; P = 0.02), Conclusion The hCG test is a valid indicato r of the presence of functioning testicular tissue, It is predictive o f anorchia and a good response to hCG suggests the presence of testes sufficiently large for orchidopexy.