Effects of Castration, Steroid Replacement, and Hypophysectomy on Hypothalamic LHRH and Serum LH

The effect of castration (CAS), hypophysectomy (HYPOX), and gonadal steroids on hypothalamic luteinizing hormone-releasing hormone (LHRH) content was studied in male and female rats. Hypothalamic LHRH content was significantly reduced by 1 week after castration in male rats and was further reduced by 2 weeks. HYPOX decreased LHRH content in male rats to the same extent as in CAS rats alone, suggesting that loss of gonadal function was mainly responsible for the fall in hypothalamic LHRH in these rats. In castrated male rats testosterone propionate (TP) at a dose of 0.5 mg/300 g body weight raised hypothalamic LHRH content above that of intact rats and reduced serum LH below the intact level. However, in castrated-hypophysecto-mized rats, TP treatment only returned hypothalamic LHRH content to the intact level.