Growth hormone (GH) plays a central role in linear growth, tissue development, and metabolic regulation during childhood and adolescence. Although GH secretion is tightly regulated by the hypothalamic–pituitary axis, it is increasingly recognized that environmental factors significantly modulate this hormonal system, either by affecting GH release directly or by altering tissue responsiveness to GH and insulin-like growth factor 1 (IGF-1). 1. Nutrition and Dietary Patterns Nutrition is one of the most influential environmental determinants of GH activity: • Chronic undernutrition is associated with reduced circulating IGF-1 levels despite normal or even elevated GH secretion, reflecting a state of GH resistance. • Protein-energy malnutrition impairs hepatic IGF-1 synthesis, limiting the growth-promoting effects of GH. • Diets rich in simple carbohydrates increase insulin secretion, which suppresses GH release. • Micronutrients such as zinc, iron, and vitamin D are essential for optimal GH–IGF-1 axis function. Importantly, growth impairment due to nutritional deficiency is often reversible with appropriate dietary rehabilitation. 2. Sleep and Circadian Rhythm Sleep is a major physiological stimulus for GH secretion: • The largest GH pulses occur during deep (slow-wave) sleep, particularly in the early part of the night. • Sleep deprivation, irregular sleep schedules, and excessive screen exposure, especially common in adolescents, reduce slow-wave sleep duration and blunt nocturnal GH secretion. • Chronic disruption of circadian rhythm may negatively affect peak height velocity during puberty. Thus, sleep quality is as important as sleep duration for normal growth. 3. Physical Activity and Sedentary Behavior Physical activity exerts a strong stimulatory effect on GH release: • Regular exercise, especially high-intensity or resistance activities, increases pulsatile GH secretion. • In contrast, sedentary lifestyle and prolonged inactivity are associated with reduced GH output. • Childhood and adolescent obesity, a growing environmental concern, is linked to suppressed GH secretion due to elevated insulin and free fatty acid levels. These effects highlight the importance of an active lifestyle during growth periods. 4. Psychological Stress and Social Environment The psychosocial environment has a profound impact on endocrine regulation: • Chronic psychological stress elevates cortisol levels, which inhibit GH secretion and interfere with IGF-1 action. • Children exposed to emotional deprivation, neglect, or unstable social environments may develop psychosocial growth failure, characterized by growth retardation without primary endocrine pathology. • Improvement in emotional and social conditions often leads to catch-up growth. This underscores the close interaction between neuroendocrine regulation and environmental stressors. 5. Chronic Illness and Recurrent Infections Environmental health conditions also influence growth hormone dynamics: • Chronic systemic diseases (e.g., renal disease, inflammatory bowel disease, chronic infections) reduce GH effectiveness by inducing inflammatory cytokines and metabolic stress. • Recurrent infections, common in low-resource settings, divert energy away from growth processes and impair the GH–IGF-1 axis. These effects are often multifactorial, involving nutrition, inflammation, and hormonal dysregulation. 6. Environmental Pollutants and Endocrine Disruptors Recent research has highlighted the role of environmental endocrine-disrupting chemicals (EDCs): • Substances such as bisphenol A (BPA), pesticides, and industrial pollutants may interfere with GH signaling or IGF-1 activity. • Chronic exposure during critical developmental periods may subtly impair growth potential, even in the absence of overt disease. This area remains under active investigation, with growing public health implications.