Urinary cortisol and muscle mass in Turkana men

To determine the role of cortisol in modulating the effects of energetics on muscle mass in a subsistence society, measures of cortisol and body composition were obtained from a sample of Turkana men. Subjects were 63 settled and 69 nomadic men, ages 24 and older. Urinary cortisol was determined along with measures of muscle mass. Cortisol/creatinine ratio was higher among nomadic men (57.8 +/- 56.8 vs. 34.5 +/- 44.6; P < 0.001). Controlled for age, urinary cortisol was inversely related to arm muscle plus bone area (MPBA) among the nomadic (beta = -0.28; P = 0.04), but not the settled (beta = -0.04; P = 0.78) sample. Urinary cortisol was not related to any other measures of body composition. These results suggest that even in chronically undernourished populations, cortisol may be elevated primarily under conditions of acute nutritional stress. However, the catabolic effects of cortisol on muscle in our results may be confounded by other energetic factors, including energy availability. Am. J. Hum. Biol. 17:489-495, 2005. (c) 2005 Wiley-Liss, Inc.