Case Report A 38-year-old Caucasian woman with no significant past medical history presented several weeks after an abrupt onset of severe occipital headache followed by marked polydipsia and polyuria, bilateral galactorrhea and secondary amenorrhea. Pituitary MRI reported a nonenhancing 7-mm pituitary microadenoma involving the midline gland with stalk contact but no optic chiasm compression. On personal review, findings favored homogeneous pituitary enlargement with stalk thickening rather than a discrete adenoma, along with absent posterior pituitary bright spot. Laboratory evaluation revealed mild hyperprolactinemia with otherwise preserved anterior pituitary function and normal serum sodium. A 24-hour urine collection confirmed polyuria with a total volume of 6 liters. Desmopressin was initiated with symptomatic improvement. Cabergoline was briefly started for galactorrhea but discontinued due to impulsivity. PRL levels normalized spontaneously with resolution of galactorrhea and amenorrhea, attributed to transient stalk dysfunction from inflammatory edema rather than a prolactinoma. Repeat MRI ten months later demonstrated marked reduction in pituitary size with normalization of the stalk, supporting a diagnosis of hypophysitis. She had no history of malignancy, autoimmune disease, or lymphoproliferative disorder. She continues to have persistent central diabetes insipidus (CDI) and is undergoing further evaluation.
Discussion Hypophysitis is an uncommon inflammatory disorder that typically presents with anterior hypopituitarism, headache, and symptoms of mass effect. Isolated CDI as an initial manifestation is rare and poses a diagnostic challenge. This atypical presentation broadens the differential diagnosis to include germinoma, Langerhans cell histiocytosis, metastatic disease, and idiopathic CDI, potentially delaying recognition of hypophysitis. Neuroimaging is critical for diagnosis, with characteristic MRI features including pituitary stalk thickening, homogeneous gland enlargement, and loss of the posterior pituitary bright spot. Recognition of these findings may prevent unnecessary invasive procedures and guide appropriate management. While pituitary biopsy remains the diagnostic gold standard, a presumptive diagnosis can often be made through integration of clinical, biochemical, and radiographic findings. Management typically includes hormone replacement, observation with serial imaging, and glucocorticoid therapy when mass effect or progressive symptoms are present.
Conclusion This case illustrates that hypophysitis, though uncommon, should be considered in patients presenting with isolated CDI, particularly when characteristic MRI findings are present, as early recognition has important diagnostic and therapeutic implications.
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