Insulin and Growth Hormone Balance: Implications for Obesity

Insulin and GH are counter-regulatory hormones in terms of glucose and lipid metabolism, but act synergistically in protein metabolism. They also mutually regulate the secretion of each other, forming a complex regulatory network. The balance between insulin and GH is associated with substrate and energy metabolism. In obesity, the hormonal imbalance (high insulin and low GH) promotes further fat accumulation. Clinical data from various physiological and pathophysiological conditions with insulin and GH changes indicate that the [insulin]:[GH] ratio correlates negatively with energy expenditure and correlates positively with fat accumulation. The [insulin]:[GH] ratio may serve as a biomarker for monitoring and predicting the development of obesity. Modulation of insulin–GH balance is a promising target for managing obesity. Disruption of endocrine hormonal balance (i.e., increased levels of insulin, and reduced levels of growth hormone, GH) often occurs in pre‐obesity and obesity. Using distinct intracellular signaling pathways to control cell and body metabolism, GH and insulin also regulate each other’s secretion to maintain overall metabolic homeostasis. Therefore, a comprehensive understanding of insulin and GH balance is essential for understanding endocrine hormonal contributions to energy storage and utilization. In this review we summarize the actions of, and interactions between, insulin and GH at the cellular level, and highlight the association between the insulin/GH ratio and energy metabolism, as well as fat accumulation. Use of the [insulin]:[GH] ratio as a biomarker for predicting the development of obesity is proposed. Disruption of endocrine hormonal balance (i.e., increased levels of insulin, and reduced levels of growth hormone, GH) often occurs in pre‐obesity and obesity. Using distinct intracellular signaling pathways to control cell and body metabolism, GH and insulin also regulate each other’s secretion to maintain overall metabolic homeostasis. Therefore, a comprehensive understanding of insulin and GH balance is essential for understanding endocrine hormonal contributions to energy storage and utilization. In this review we summarize the actions of, and interactions between, insulin and GH at the cellular level, and highlight the association between the insulin/GH ratio and energy metabolism, as well as fat accumulation. Use of the [insulin]:[GH] ratio as a biomarker for predicting the development of obesity is proposed. a condition in which the pituitary produces excessive GH during adulthood, mostly due to a pituitary adenoma. the pituitary is unable to produce sufficient GH because of primary lesion. Childhood-onset GH deficiency is mainly due to genetic defects, whereas adult GH deficiency can be caused by multiple factors including trauma, infections, tumors, or radiation therapy. Reduced secretion of GH in obesity does not belong to this category in this review. However, it is often referred as 'relative GH deficiency' in obesity in most literature. IGF-1 is produced by a variety of cell types following GH stimulation. Circulating IGF-1 is mainly produced by the liver and acts as a negative regulator of GH secretion. Local IGF-1 produced by bone and muscle contributes to linear growth and protein anabolism. according to the World Health Organization, obesity is defined as a body mass index (BMI, body weight in kg divided by height in m squared) of 30 or more. a drug used for treating acromegaly in the clinic that blocks downstream signaling of the GH receptor. It is a modified version of human GH that competes with native GH for the GH receptor and prevents its activation. an important endocrine organ located in the brain, under the hypothalamus. It responds to hormonal signals from the hypothalamus (e.g., GH-releasing hormone) and produces hormones (e.g., GH) to regulate body functions. an antidiabetic drug that increases insulin secretion by closing ATP-sensitive potassium channels on pancreatic β cells.