Obesitogenic Hypothyroidism: Diagnostic Challenges and Therapeutic Implications in Modern Endocrinology

Obesity and hypothyroidism frequently coexist in clinical practice, yet the nature of their relationship remains incompletely understood. While traditional teaching attributes weight gain to thyroid hormone deficiency, growing evidence suggests that excess adiposity itself can alter thyroid physiology. Obesity is associated with mild elevations in thyroid-stimulating hormone, often with normal free thyroxine levels, raising diagnostic uncertainty regarding true hypothyroidism versus a reversible, adaptive response. Adipokine imbalance, chronic low-grade inflammation, altered deiodinase activity, and immune dysregulation appear to mediate this interaction. This narrative review synthesizes current evidence on the epidemiology, pathophysiology, diagnostic challenges, and clinical implications of obesity-associated thyroid dysfunction, for which the term obesitogenic hypothyroidism is proposed. Emphasis is placed on distinguishing adaptive hyperthyrotropinemia from primary autoimmune thyroid disease to avoid unnecessary lifelong levothyroxine therapy. Recognizing this phenotype has important implications for rational investigation, individualized treatment decisions, and long-term metabolic outcomes.