The influence of feed restriction and subsequent re-feeding on gonadotrophin secretion and serum testosterone levels in male rats.

Male rats at 3 months were fully fed or were restricted to 50% of normal feed intake for 10 or 20 days. Underfeeding for either period resulted in reduced (P less than 0-05) body weight and pituitary weight but did not affect testicular weight. Underfeeding for 20 days resulted in reduced (P less than 0-05) weights of the seminal vesicles and ventral prostate. The serum concentration of LH was depressed (P less than 0-05) after 10 days of underfeeding and the pituitary concentration of LH was elevated (P less than 0-05) after 20 days of underfeeding. Neither serum nor pituitary concentration of FSH was influenced by feed level. Serum testosterone concentration was reduced in rats underfed for 20 days. In a second study, 2-month-old males were fully fed, underfed (15 days) or underfed and then re-fed (full feed) for 1, 2, 3 or 7 days. Underfeeding produced effects similar to those noted in the first experiment. Re-feeding of underfed rats resulted in body and ventral prostate weights returning to levels similar to those of fully fed controls by Day 7. The serum level of FSH was elevated (P less than 0-05) above the control level on Days 1, 3 and 7 of re-feeding, while the serum level of LH appeared to return to the control level. Serum testosterone level rebounded and exceeded (P less than 0-05) the control level on Days 1 and 2 of re-feeding.