Serum inhibin B, FSH, LH and testosterone levels before and after human chorionic gonadotropin stimulation in prepubertal boys with cryptorchidism

University Department of Growth and Reproduction, GR-5064, Rigshospitalet, Denmark. peter.c@dadlnet.dk

BACKGROUND: Several studies have indicated that cryptorchidism is associated with degenerative changes in both Sertoli cells and germ cells. The gonadal peptide hormone inhibin B reflects Sertoli cell function. Low inhibin B levels are found in a large portion of formerly cryptorchid men who show compromised seminiferous tubule function. It is not known if inhibin B can be used to demonstrate early damage of seminiferous tubules in prepubertal boys with cryptorchidism. METHODS: We investigated the relationship between serum levels of inhibin B, testosterone, FSH and LH in 62 prepubertal boys with uni- and bilateral cryptorchidism. Furthermore, we investigated the changes in serum levels of inhibin B and the corresponding changes in serum levels of FSH, LH and testosterone during a short course (3 weeks) of human chorionic gonadotropin (hCG) injections in 18 of these cryptorchid boys. RESULTS: In the 62 prepubertal boys with uni- or bilateral cryptorchidism there were no significant differences in baseline levels (median and range) of inhibin B (88 (20-195) pg/ml vs 78 (35-182) pg/ml; not significant), LH (0.08 (<0.05-0.99) IU/l vs 0.06 (<0.05-1.61) IU/l; not significant) and FSH (0.60 (0.08-3.73) IU/l vs 0.85 (0.25-2.55); not significant) compared with 156 healthy prepubertal boys, and there were no differences in hormonal levels between boys with uni- or bilateral cryptorchidism. There was no correlation between baseline levels of inhibin B and FSH. In boys younger than 9 years, we found no correlation between baseline levels of inhibin B and LH whereas, in boys older than 9 years, baseline levels of inhibin B were positively correlated to baseline LH (Spearman rank correlation coefficient ((R(s))=0.58, P=0.03). Treatment with hCG (1500 IU intramuscularly twice weekly for 3 weeks) resulted in descensus of testes in 9 out of 18 patients. In all boys but one, irrespective of age, hCG induced a marked increase in testosterone into the adult range (from undetectable to 21.8 (7.0-35.4) nmol/l; P<0.001) and completely suppressed FSH and LH levels. Serum levels of inhibin B increased significantly from 116 (50-195) pg/ml to 147 (94-248) pg/ml (P<0.05), but not uniformly. The increase in serum levels of inhibin B was inversely correlated to baseline inhibin B (Rs=-0.52, P=0.03) and baseline FSH (R(s)=-0.59, P<0.01). CONCLUSIONS: We therefore suggest that, in the prepubertal testes, inhibin B is secreted from the prepubertal Sertoli cells following hCG, whereas early pubertal testes with more differentiated Sertoli cells are not able to secrete inhibin B in response to hCG stimulation, perhaps due to lack of germ cell-derived betaB-subunits. We found (a) normal inhibin B levels in prepubertal boys with uni- or bilateral cryptorchidism, (b) that hCG stimulated testosterone markedly and suppressed FSH and LH levels and (c) that hCG treatment stimulated inhibin B levels in the youngest cryptorchid boys. In the oldest prepubertal boys no hCG-induced changes in inhibin B were shown.

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