An unusually small pituitary microadenoma causing severe Cushing disease in a male patient: lessons from early Radiosurgical management.

Cushing disease is a rare endocrine disorder caused by an ACTH-secreting pituitary adenoma. We report a 27-year-old male with severe hypercortisolism due to a 1.2-mm pituitary microadenoma. He presented with facial plethora, centripetal obesity, violaceous striae, hypertension, diabetes, dyslipidemia, and fatigue. Biochemical testing confirmed ACTH-dependent hypercortisolism, and 3 T MRI identified the lesion. Owing to its minute size and the anticipated difficulty of surgical localization, transsphenoidal surgery was deferred and Gamma Knife radiosurgery (GKRS) was performed as first-line therapy. After 5 months, biochemical hypercortisolism persisted, with elevated cortisol and ACTH levels. Ketoconazole 200 mg daily was subsequently initiated, resulting in normalization of serum cortisol within four weeks, ACTH levels remained elevated. Mild transient ALT elevation was observed during treatment. This case highlights that very small adenomas can cause severe disease and underscores the delayed response to GKRS, necessitating early adjunctive medical therapy to control hypercortisolism and reduce morbidity.