Adipsic hypernatremia associated with hypothalamic dysfunction and sleep disorders.

Adipsic hypernatremia is a rare hypothalamic disorder characterized by impaired thirst despite preserved renal concentrating ability and may coexist with multisystem neuroendocrine and sleep disturbances. We report a 20-year-old male with beta-thalassemia minor presenting with severe hypernatremia with serum sodium of 170 mEq/L (SI: 170 mmol/L) (reference range 133-146 mEq/L [SI: 133-146 mmol/L]), absent thirst, weight loss, fatigue, hypogonadotropic hypogonadism, and hyperprolactinemia, along with excessive daytime sleepiness, hypnagogic hallucinations, and emotion-triggered cataplexy. Laboratory evaluation confirmed preserved renal concentrating ability, and pituitary magnetic resonance imaging was normal. Findings were consistent with adipsic hypernatremia due to functional hypothalamic dysfunction, with coexisting severe obstructive sleep apnea confirmed on polysomnography (apnea-hypopnea index [AHI] 35.9 events/hour) and presumed narcolepsy with cataplexy. Management included structured fluid intake, testosterone replacement, cabergoline, wake-promoting agents (modafinil, methylphenidate), and continuous positive airway pressure therapy. This case underscores the complex interplay between hypothalamic dysfunction, endocrine abnormalities, and sleep disorders, highlighting the importance of early recognition and structured management to prevent recurrent hypernatremia and optimize clinical outcomes.