Disruption of pubertal onset by exogenous testosterone and estrogen in two species of rodents

Abstract

The administration of adult physiological levels of testosterone (T) and 17β-estradiol (E2) to male Siberian hamsters was previously shown to delay the onset of puberty. To examine whether this is a response common to other rodents, we investigated whether exogenous steroids also alter the onset of puberty in Syrian hamsters and mice. Juvenile male Syrian hamsters and mice were implanted with Silastic capsules containing T, E2, or cholesterol control. After 15 days, plasma, pituitaries, and testes were processed for histological analysis or measurements of gonadotropins and circulating steroid hormones. T and E2implants reduced testis mass and gonadotropin stores in both species and arrested spermatogenesis in Syrian hamsters. In contrast, spermatogenesis in mice was unaffected by T and only modestly affected by E2. Although E2 inhibited circulating follicle-stimulating hormone (FSH) in both species, T inhibited circulating FSH in mice only. Overall, our results demonstrate that the hypothalamic-pituitary-gonadal axis of each rodent species responds uniquely to T and E2 during the pubertal transition. Despite the highly varied effects of T and E2 in these two species, the ability of steroid hormones to disrupt the onset of puberty appears to be a feature common to many rodents.