Growth hormone and experimental cancer cachexia

Plasma levels of growth hormone (GH) and the effect of GH treatment have been evaluated in adult nongrowing sarcoma-bearing mice (C57BL/6J). Prepubertal tumor-bearing mice, tumor-bearing hypophysectomized Sprague-Dawley rats, and malnourished non-tumor-bearing animals served as additional groups of study and control animals. Adult sarcoma-bearing mice showed an increase in plasma levels of GH early following tumor implantation. GH levels increased further with tumor progression. The anorexia and the state of malnutrition in sarcoma-bearing mice were the major factors behind increased GH levels. Muscle wasting and body composition in the tumor-bearing host were not improved by GH treatment at doses that increased growth rate in normal growing mice with intact pituitaries or partially normalized growth rate in hypophysectomized rats. Exogenous GH supported tumor growth and host body growth to the same extent in hypophysectomized rats. Exogenous GH in excess of endogenous GH did not stimulate tumor growth further. It is suggested that increased GH production in a tumor-bearing host acts in concert with other hormones to stimulate endogenous substrate mobilization and in tumor-bearing animals to prevent substrate deficiency and hypoglycemia. On the basis of this conclusion, it is unlikely that GH supplementation to a freely eating tumor-bearing host will support replenishment of host tissues.