STAT5B and obesity due to melanocortin 4 receptor deficiency: These findings highlight two physiological aspects of GHR-STAT5 signaling: (1) the anti-obesity actions of GH are enhanced by the pulsatility of GH secretion evident in males because of pulsatile STAT5 activation and (2) despite normal plasma FFA and minimal adiposity, absent GHR activation lead to hepatic steatosis because of reduced STAT5 activation, which prevents this pathology (Lichanska and Waters, 2008).