Overlapping pathologies: Adrenal insufficiency presenting as refractory acute heart failure.

Isolated adrenocorticotropic hormone (ACTH) deficiency is a rare form of secondary adrenal insufficiency that may be unmasked by physiological stress such as rapid atrial fibrillation (AF) or acute heart failure. We report the case of a 69-year-old male patient with tachycardiac AF-induced acute decompensated heart failure (ADHF), in whom persistent hyponatremia and hypotension were unresponsive to inotropic support and fluid resuscitation. Endocrine evaluation revealed markedly decreased ACTH and cortisol levels, with preservation of other pituitary hormones, confirming isolated ACTH deficiency. Prompt administration of hydrocortisone led to rapid improvement in hemodynamics and electrolyte balance. This case highlights the diagnostic challenge posed by overlapping features of adrenal crisis and ADHF. Adrenal insufficiency should be considered in cases of refractory heart failure with persistent hyponatremia and hypotension. Empirical corticosteroid therapy may be lifesaving and should not be delayed while awaiting hormonal confirmation. Learning objectives: Isolated adrenocorticotropic hormone deficiency is a rare form of secondary adrenal insufficiency that can be unmasked by stress conditions such as rapid atrial fibrillation or acute heart failure. In cases of refractory heart failure with persistent hyponatremia and hypotension despite inotropic support and fluid resuscitation, adrenal insufficiency should be considered a critical differential diagnosis. When adrenal crisis is suspected, empirical corticosteroid therapy may lead to rapid hemodynamic improvement, even before hormonal confirmation.