Hyponatremia: An Unusual Presentation of Hypophysitis

The most frequently observed dyselectrolytemia encountered in daily clinics is hyponatremia. Our patient presented with hyponatremia due to hypophysitis, seen as low serum cortisol, normal adrenocorticotropic hormone (secondary adrenal insufficiency), and, on evaluation, other pituitary hormones, such as thyroid stimulating hormone, follicle stimulating hormone, and luteinizing hormone, were also low, suggestive of panhypopituitarism. This case report focuses on a 54-year-old male who came with generalized weakness, sleep disturbances, and myalgias. Initial investigations revealed hyponatremia, eosinophilia, and low serum cortisol. Pituitary magnetic resonance imaging demonstrated a mildly bulky pituitary with a thickened stalk. Subsequent hormonal evaluation confirmed panhypopituitarism. Elevated serum immunoglobulin G4 (IgG4) levels and typical pituitary image findings led to probable IgG4-related hypophysitis and responded well to corticosteroid therapy. On follow-up, serum sodium levels were within normal limits. This case report underscores the significance of including IgG4-related hypophysitis in the differential diagnosis for patients presenting with hyponatremia and pituitary abnormalities.