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Testosterone metabolic clearance rate and production rate in the male infant rhesus monkey
Insights
Infant male rhesus monkeys show rising testosterone levels due to increased production, not slower metabolism. This study investigates the hormonal changes in young male monkeys.
Area of Science:
- Endocrinology
- Reproductive Biology
- Primate Studies
Background:
- Male infant rhesus monkeys exhibit a distinct phase of testicular activation post-birth.
- Plasma testosterone concentrations in infant rhesus monkeys peak around 1-3 months and then decline significantly by 60 months.
Purpose of the Study:
- To elucidate the physiological mechanisms behind the transient rise in plasma testosterone levels observed in infant male rhesus monkeys.
- To differentiate between altered hormone production and changes in metabolic clearance as the cause of elevated testosterone.
Main Methods:
- Measurement of plasma testosterone metabolic clearance rates (MCRT) and production rates (PRT) in two infant rhesus monkeys at 1 and 6 months of age.
- Utilized established techniques for pharmacokinetic analysis of hormone levels in primate models.
Main Results:
- Metabolic clearance rates (MCRT) for testosterone showed minimal variation between 1 and 6 months of age.
- Testosterone production rates (PRT) were significantly higher at 1 month compared to 6 months of age, indicating increased synthesis.
- These findings correlate with the observed peak and subsequent decline in plasma testosterone concentrations.
Conclusions:
- The transient increase in plasma testosterone in infant male rhesus monkeys is primarily driven by an elevated production rate.
- Hormone metabolism and clearance do not appear to be the main factors responsible for these early-life hormonal fluctuations.
- This research provides insight into primate reproductive endocrinology during early development.
Abstract:
The male infant rhesus monkey (Macaca mulatta) undergoes a period of testicular activation similar to that seen in the human infant. Plasma testosterone (T) concentrations rise after birth, reaching levels of about 500 ng/dl at 1-3 mo of age and then fall to approximately 50 ng/dl at 60 mo. The plasma T metabolic clearance rates (MCRT) and production rates (PRT) were measured in two rhesus infants at 1 and 6 mo of age to determine the mechanism of the observed increase in plasma T. While there was little change in the MCRT between 1 and 6 mo, PRT was much higher at 1 mo than at 60 mo of age. These observations are consistent with the hypothesis that the increased plasma testosterone levels in infant rhesus monkeys reflect an increased production of testosterone rather than an altered metabolic disposition of the hormone.