Recovery of Testicular and Pituitary Functions in Adult Male Rats after Cessation of Short and Long Term Estradiol Treatment

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Abstract
Recovery of the gonadal-pituitary axis in intact adult male rats was investigated for 15 days after a single injection of estradiol benzoate (EB), and for 60 days after 14 daily injections of EB. After a single injection of EB, plasma and testicular levels of testosterone (T) were suppressed for 2 days, but recovered to control levels by Day 4 and thereafter. Plasma LH, however, was significantly suppressed 4 and 6 days into recovery, while T had returned to normal values. During this time, the mean pituitary content and concentration of LH were decreasing and, although these decreases were not statistically significant, they may point to possible EB suppression of LH synthesis. On the other hand, plasma FSH significantly decreased 2 days after treatment, while pituitary FSH concentration and content were significantly increased, indicating that EB suppressed the pituitary release, but not the synthesis of FSH.