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Human chorionic gonadotrophin (hCG) stimulates spermatogenesis in immature mice in vivo.

BACKGROUND/PURPOSE
Spermatogenesis in postnatal testes is controlled by the hypothalamic-pituitary-gonadal axis. To determine if pituitary hormones can induce precocious spermatogenesis once primary spermatocytes (PS) have formed, prepubertal mice were treated with human chorionic gonadotrophin (hCG).


METHODS
Day 12 immature mice (n = 10) were injected every third day with hCG (3 or 6 IU) dissolved in 100 microL phosphate-buffered saline (PBS). Control mice (n = 10) were either uninjected or injected with 100 microL PBS alone. On day 20 to 22 the excised testes were examined histologically with tubule counts.


RESULTS
HCG-treated mice had fewer tubules at stage I (P <.001) and more at stage III than the PBS-treated group (P <.001). Mean thickness of the round spermatid layer per tubular cross section in the hCG-treated group was significantly increased compared with the PBS-treated group (P <.01). Similarly, the percentage of the tubules at stage III (containing round spermatids) in the hCG-treated group was significantly increased, from 25% to 71%, compared with the PBS-treated group (P <.01). With increasing doses of hCG the testosterone levels were significantly higher than in controls (P <.01), but hCG did not alter testis weight or position.


CONCLUSIONS
These results show that hCG stimulates the transformation of PS to round spermatids even in immature mouse testes. These findings suggest that hCG treatment of prepubertal cryptorchid boys may initiate premature spermatogenesis.