All issues > Volume 35(2); 1992

Original Article

J Korean Pediatr Soc. 1992;35(2):174-181. Published online February 15, 1992.

The Effects of Testosterone on the Pituitary Growth Hormone Secretion

Ho Seong HS Kim¹, Duk Hi DH Kim¹, Kyung Za KZ Ryu², Chang Mee CM Kim³, Deok Bae DB Park³

¹Department of Pediatrics, College of Medicine, Yonsei University, Seoul, Korea
²Department of Pharmacology, College of Medicine, Yonsei University, Seoul, Korea
³Endocrine Laboratory, College of Medicine, Yonsei University, Seoul, Korea

Abstract

The effects of testosterone on growth hormone secretion and somatic growth have been reported in several previous studies. In order to investigate the role of testosterone in growth hormone secretion, we have studied the effect of testosterone on somatic growth, basal growth hormone concentration, and growth hormone response to growth hormone-releasing hormone (GHRH) in orchiectomized rats. In experiment 1, four groups (five rats per group) of 230-g sexually matured male Wistar rats were orchiectomized and thereafter recieved s.c. injection of testosterone propionate (0.1mg, 1mg, and 10mg) or vehicle (olive oil) for 20 days. A fifth group was underwent sham operation and received vehicle injections. Blood for basal growth hormone determination was drawn right after orchiectomy and on the 10th and 20th day after orchiectomy. Body weight and tail length were measured at the beginning and the end of experiment in all groups. On the 20th day, 500 ng/kg human GHRH-(1-29)-NH2 was injected into a tail vein. Blood for growth hormone measurement was collected before and 5,10 min after GHRH administration. In experiment 2, five rats were orchiectomized and thereafter received s.c.injections of testosterone propionate (1mg). After the orchiectomy, on the 10th, 20th day, 500ng/kg GHRH were injected and blood for growth hormone was drawn before and 5,10 min after GHRH administration. The increase in body weight and tail length during testosterone treatment was not significant. The treatment of testosterone for 20 days after orchiectomy significantly increased basal growth hormone concentrations compared with that of vehicle-treated rats after orchiectomy. The maximum growth hormone response to GHRH in 1mg or 10 mg testosterone-treated rats after orchiectomy was significantly greater than that of vehicle-treated rats after ochiectomy. And there was positive correlation between maximum growth hormone response to GHRH and testosterone doses treated. The growth hormone response to GHRH was not changed with the duration of testosterone treatment. These results demonstrated that testosterone stimulates growth hormone secretion by modulating the pituitary growth hormone response to GHRH.

Keywords :Testosterone, Growth hormone secretion