Sarcopenia, defined as the progressive loss of skeletal muscle mass, strength, and function with aging, is a key determinant of frailty, disability, and mortality in older adults. Beyond reduced physical activity and malnutrition, accumulating evidence highlights a central role of endocrine dysfunction in its pathogenesis. Age-related declines in anabolic hormones such as testosterone, dehydroepiandrosterone, growth hormone, insulin-like growth factor 1, estrogen, compromise muscle protein synthesis, regeneration, and metabolic efficiency. Simultaneously, increased levels or altered action of catabolic factors such as glucocorticoids and components of the renin–angiotensin–aldosterone system promote muscle degradation and inhibit repair. Moreover, metabolic and signaling molecules including leptin, ghrelin, myostatin, and follistatin modulate muscle homeostasis through complex endocrine and paracrine pathways. This chapter explores the multifaceted hormonal regulation of muscle biology in aging, emphasizing both the detrimental and protective roles of different endocrine signals. A comprehensive understanding of these mechanisms is essential for developing targeted interventions aimed at preserving muscle mass and function and for designing hormone-based strategies to prevent or treat sarcopenia across the lifespan.