Seasonal changes in the thyroid hormones of the male squirrel monkey

The serum of male squirrel monkeys was analyzed for levels of thyroxine (T4) and triiodothyronine (T3) at intervals corresponding to (1) preparations for breeding, (2) termination of breeding, and (3) well after the breeding season. Highest concentrations of hormones were found prior to breeding when body weight was also highest. Significant differences in hormone levels were found across sampling period. The interaction between gonadotropins and thyroid hormones is discussed.