Obesity, growth hormone and weight loss

Abstract

Growth hormone (GH) is the most important hormonal regulator of postnatal longitudinal growth in man. In adults GH is no longer needed for longitudinal growth. Adults with growth hormone deficiency (GHD) are characterised by perturbations in body composition, lipid metabolism, cardiovascular risk profile and bone mineral density. It is well established that adult GHD usually is accompanied by an increase in fat accumulation and GH replacement in adult patients with GHD results in reduction of fat mass and abdominal fat mass in particular. It is also recognized that obesity and abdominal obesity in particular results in a secondary reduction in GH secretion and subnormal insulin-like growth factor-I (IGF-I) levels. The recovery of the GH IGF-I axis after weight loss suggest an acquired defect, however, the pathophysiologic role of GH in obesity is yet to be fully understood. In clinical studies examining the efficacy of GH in obese subjects very little or no effect are observed with respect to weight loss, whereas GH seems to reduce total and abdominal fat mass in obese subjects. The observed reductions in abdominal fat mass are modest and similar to what can be achieved by diet or exercise interventions.

Immunoreactive and bioactive growth hormone responses to resistance exercise in men who are lean or obese

“…It is also well established that increased body fat and body mass index (BMI) suppress spontaneous and stimulated serum GH concentrations but that these pulsatile responses return to normal with reduction to normal levels of body weight (43,46). Normal GH response to physiological stimuli such as sleep and cardiovascular exercise appears to be impaired in obese individuals (44). Lower cardiovascular exercise-induced GH secretions have been attributed to a reduction in the mass of GH secreted per pulse (26,50).…”

IGF1 modifications after bariatric surgery in morbidly obese patients: potential implications of nutritional status according to specific surgical technique

“…Hyperinsulinism and insulin resistance, increased free fatty acids, and hyperleptinemia are additional factors that may contribute to the functional disturbances of the somatotropic axis in MO subjects (9,24). Most of these factors, if not all, show dramatic changes after surgically induced WL and may participate with more or less impact in the improvement of IGF1 after surgery.…”

“…In this context, it has also been demonstrated that GH secretion is impaired in obese patients (4,9). In fact, GH levels in some obese patients have been found to be as low as in adult patients with organic GH deficiency (9,10). Somatotropic insufficiency has been associated with cardiovascular disease and an excessive cardiovascular morbidity and mortality in those patients with untreated GH deficiency (11), so obese subjects with functional deficiency of the somatotropic axis could also have an additional reduction in their life expectancy due to this fact.…”

“…Different studies have recently demonstrated the improvement of obesityrelated endocrine comorbidities after treatment with bariatric surgery (4,5,6,7,8). In this context, it has also been demonstrated that GH secretion is impaired in obese patients (4,9). In fact, GH levels in some obese patients have been found to be as low as in adult patients with organic GH deficiency (9,10).…”

“…GH has an important anabolic function in hepatic and muscle tissues and lipolytic actions in adipose tissue (12). Insulin-like growth factor 1 (IGF1) has been reported to be low in a substantial proportion of patients with severe obesity in association with normal or high concentrations of its binding proteins (IGFBPs), mostly IGFBP3 (9,12). This functional GH deficiency state in obesity is not always reversed after hypocaloric diet, while weight loss (WL) obtained by bariatric surgery seems to be more effective in doing so (13,14,15,16,17,18,19,20,21,22,23,24).…”