Occult Adrenal Insufficiency Masquerading as Recurrent Hyponatremia in a Treated Hypothyroid Patient: The Diagnostic Challenge of "Endocrine Silence"

Recurrent hyponatremia is a common yet diagnostically challenging clinical entity, particularly when classical features of underlying endocrine disorders are absent. Adrenal insufficiency remains an under-recognized but potentially life-threatening cause. We report a case of a 50-year-old female with well-controlled hypothyroidism who presented with chronic fatigue and multiple prior hospitalizations for hyponatremia over five years. She developed acute gastrointestinal symptoms with persistent hyponatremia and episodes of hypotension despite adequate fluid resuscitation. Laboratory evaluation revealed inappropriately elevated urine sodium, suggesting a non-hypovolemic etiology. The absence of hyperpigmentation, hyperkalemia, or severe hemodynamic instability masked the diagnosis. This case highlights the concept of “endocrine silence,” wherein secondary adrenal insufficiency presents without classical clinical markers, leading to delayed diagnosis. Early recognition through targeted endocrine evaluation is crucial to prevent recurrent morbidity and potential adrenal crisis.