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Abstract:
Male and female rats receiving estradiol from weanling to early adulthood displayed a reduction in body weight gain and skeletal growth over the entire treatment period. At 76 days of age exogenous estrogen was discontinued and bilateral ovariectomies were performed on the females. The 17-week posthormone period was characterized by an accelerated rate of growth of both sexes; however, only the male rats had posthormone growth rates that indicated total compensation for the early depressant effects of estrogen. These results argue against recent proposals suggesting that mechanisms regulating the body weight and growth of rats are insensitive to estrogen until the onset of natural puberty. It is not clear from the present work what mechanism is responsible for the reduced growth. However, the similarities of the somatic growth effects of estradiol, as noted here, and the effects of undernutrition on young rats suggest that hypophagia may cause the depression of growth noted during estrogen treatment.