Objective: To review retrospectively the value of the human chorionic gonadotrophin (hCG) test in the evaluation of prepubertal boys with bilateral impalpable testes.
Subjects and methods: The study comprised 31 boys investigated between 1974 and 1990 at the Hospital for Sick Children, London. All boys had an hCG test consisting of three intramuscular injections of hCG on successive days at a daily dose dependent on their 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 hCG, 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 elevation after this stimulatory test. The hCG test therefore had a positive predictive value of 89% and a negative predictive value of 100%. There was a quantitative difference in testosterone response between 14 boys who had bilateral intra-abdominal testes of 'normal' volume (median pre/post ratio, 11.4) and nine boys who had an otherwise reduced volume of testes (dysplastic or unilateral intra-abdominal) (median pre/post ratio of 4; P = 0.02).
Conclusion: The hCG test is a valid indicator of the presence of functioning testicular tissue. It is predictive of anorchia and a good response to hCG suggests the presence of testes sufficiently large for orchidopexy.