Chapter 48: Endocrine Regulation of Growth and Body Mass

Growth hormone serves as the primary endocrine driver of longitudinal bone growth and lean tissue expansion, acting both directly on target tissues and indirectly through insulin-like growth factor 1, a hepatic-derived mediator that stimulates skeletal growth and metabolic processes. The chapter explores how growth hormone secretion is controlled by hypothalamic releasing hormones, including growth hormone-releasing hormone and somatostatin, which together establish pulsatile patterns of hormone release essential for optimal growth velocity. Thyroid hormones amplify the effects of growth hormone and are fundamental for normal skeletal development, neurological maturation, and metabolic rate, with their deficiency during critical developmental windows resulting in severe growth impairment. Insulin promotes anabolic processes including protein synthesis and glucose utilization, contributing to growth trajectory alongside its role in energy homeostasis. Sex hormones, particularly testosterone and estrogen, drive the pubertal growth acceleration and ultimately influence final adult stature through their effects on bone maturation and epiphyseal plate closure. The chapter addresses how nutritional status, chronic illness, psychological stress, and genetic factors modulate these endocrine pathways to determine growth outcomes. Clinical conditions such as growth hormone deficiency, thyroid dysfunction, gonadal dysgenesis, and constitutional growth delays illustrate how disruptions in endocrine signaling manifest as growth disorders. Additionally, the chapter discusses body mass regulation through hypothalamic centers that integrate signals from adipose tissue-derived hormones including leptin and adiponectin, as well as gastrointestinal satiety hormones such as ghrelin and peptide YY, which collectively establish energy balance set points and feeding behaviors that maintain long-term weight stability.