A rare case of hyponatremia

Autoimmune hypophysitis (AH) is a rare inflammatory condition characterized by the immune-mediated destruction of the pituitary gland, leading to pituitary dysfunction. While AH predominantly affects females in their childbearing years, its occurrence in older males, especially at the age of 59, is exceptionally rare. Here, we discuss AH in a middle-aged male who presented with atypical symptoms. A 59-year-old male with no known co-morbidities presented with a 2-week history of headache with retro-orbital pain, accompanied by decreased appetite, fatigue, nausea, vomiting, blurred vision and low-grade fever (for 3 days). The patient also gave a history of hepatitis B infection twenty years ago. On examination, he had icterus, while vital signs and systemic examination were within normal limits. Laboratory investigations revealed elevated C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), unconjugated hyperbilirubinemia, and hyponatremia. Further evaluation of hyponatremia revealed low serum osmolality, increased urine spot sodium, and urine osmolality, suggestive of euvolemic hyponatremia. Hormonal assays indicated low levels of T4, thyroid stimulating hormone (TSH), cortisol, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone, suggestive of pituitary dysfunction. Magnetic resonance imaging (MRI) of the brain and pituitary gland revealed a bulky pituitary gland with thickening of stalk, suggesting hypophysitis.