A Case of Spontaneously Resolving Cushing Disease

We report a case of spontaneous resolution of Cushing disease (CD). A 20-year-old female individual, previously healthy, was referred for investigation of galactorrhea and a prolactin level of 31 ng/mL (<20 ng/mL) (SI: 31 µg/L, <20 µg/L). A magnetic resonance imaging (MRI) scan revealed an 11 mm pituitary lesion. Cabergoline was commenced to address symptomatic hyperprolactinemia. Over the following months, signs of hypercortisolism evolved. Initial tests revealed a positive 1-mg dexamethasone suppression test (DST), prompting further evaluation. Midnight salivary and 24-hour urinary free cortisol tests confirmed hypercortisolism, consistent with a pituitary source which was confirmed with a peripheral corticotropin-releasing hormone (CRH) stimulation test. While cabergoline successfully resolved the galactorrhea, an MRI scan 6 months later showed an increase in the pituitary lesion's size, leading to neurosurgical referral. However, a preoperative MRI surprisingly revealed complete resolution of the pituitary mass, which coincided with the normalization of hypercortisolism symptoms and laboratory results. This rare case of spontaneous remission, while possibly influenced by cabergoline or undetected pituitary apoplexy, contributes valuable insights into the unpredictable nature of CD and its treatment.