Obesity and growth hormone secretion

Abstract

Growth hormone (GH) secretion is reduced in obesity, particularly in association with increased visceral adiposity. Although obesity-related reductions in GH may reach levels similar to those found in pituitary GH deficiency, the changes in GH due to obesity are entirely reversible with weight loss. Total IGF-1 is unchanged or modestly reduced in obesity, and free or bioavailable IGF-I appears to be unchanged or modestly increased. Thus the physiological effects of obesity-related reductions in GH are primarily due to those actions of GH that are independent of IGF-I, whereas IGF-I mediated processes such as growth are generally unaffected. In obese individuals, reduced GH is independently associated with dyslipidemia and increased markers of cardiovascular risk. Investigation of GH treatment in obese individuals has shown benefits to ameliorate dyslipidemia, decrease markers of systemic inflammation, and improve cardiovascular risk measures. However, GH treatment may also exacerbate insulin resistance, particularly in the short term. At present, the use of GH in obesity remains entirely investigational. An understanding of changes in the GH-IGF-I axis that occur in obesity is critical to the interpretation of tests evaluating this axis. Further, investigation of GH in obesity highlights potential effects on metabolic parameters and body composition that may inform the clinical use of GH in other indications.