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Methylphenidate Hydrochloride Delays Puberty in Monkeys

MPH tied to delayed testicular descent, reduced testicular volume and serum testosterone levels

WEDNESDAY, Sept. 21 (HealthDay News) -- Methylphenidate hydrochloride (MPH) delays pubertal progression with impaired testicular descent, reduced testicular volume, and decreased serum testosterone levels in juvenile male rhesus monkeys, according to an experimental study published online Sept. 19 in the Proceedings of the National Academy of Sciences.

Donald R. Mattison, M.D., from the National Institutes of Health in Bethesda, Md., and colleagues investigated the genetic and behavioral effect of MPH on the reproductive axis and puberty in juvenile male rhesus monkeys. The animals were randomized to orally receive either a vehicle or low- or high-dose MPH twice daily for 40 months. Pubertal development was assessed by measuring testicular volume and descent, plasma hormone concentrations, and semen parameters every month.

The investigators found that, after 14 months of treatment, the monkeys had delayed pubertal progression with impaired testicular descent and reduced testicular volume. There was a significant reduction in testicular volume at months 15 to 19 and at month 27 in all dose groups, but testicular descent was significantly delayed only in the high-dose group. Animals in both the low- and high-dose groups had significantly lower serum testosterone levels through month 33 of treatment. There was an overall increase in serum inhibin B levels in the low-dose group, but the between-group differences resolved by the end of the study.

"Our findings indicate that MPH administration, beginning before puberty, and which produced clinically relevant blood levels of the drug, impaired pubertal testicular development until ~5 years of age," the authors write. "The impact of MPH on puberty is not permanent."

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