Late-onset and functional hypogonadism in aging men: an integrated perspective on hormonal, sleep, and metabolic dimensions

BACKGROUND AND OBJECTIVE: Male reproductive aging is characterized by gradual hormonal and metabolic deterioration, often described as late-onset hypogonadism (LOH) or "andropause". However, these terms remain controversial and insufficient to capture the multifaceted nature of this process. This narrative review provides an integrated perspective on the interconnected hormonal, metabolic, sleep-related, and sexual consequences of male aging, with particular attention to the distinction between LOH and functional hypogonadism. METHODS: We synthesized current literature on hormonal decline, sleep disturbances, and metabolic dysfunction in aging men, with a focus on physiological mechanisms, clinical manifestations, and integrative management strategies. KEY FINDINGS AND LIMITATIONS: Progressive testosterone decline interacts with circadian disruption, sleep disorders, and metabolic imbalance in a bidirectional and clinically relevant manner. Unlike the abrupt hormonal changes in women, male decline is subtle, frequently underdiagnosed, and associated with reduced libido, fatigue, muscle loss, mood disturbances, and visceral adiposity. Sleep disturbances, including insomnia, sleep fragmentation, and obstructive sleep apnea, act both as consequences and amplifiers of endocrine and metabolic dysfunction. Current diagnostic criteria for LOH remain debated, limiting clinical recognition and delaying interventions. The distinction between LOH and functional hypogonadism is clinically meaningful, as the latter may be partially reversible through weight reduction, metabolic optimization, physical activity, and sleep-focused interventions. This review is narrative in nature, which may restrict systematic generalization of findings. CONCLUSIONS AND CLINICAL IMPLICATIONS: An integrated perspective on male reproductive aging that incorporates hormonal, metabolic, and sleep-related dimensions supports earlier diagnosis and personalized therapeutic strategies, with implications for improving men's health, quality of life, and longevity.