A rare case of dual hormone-secreting pulmonary neuroendocrine tumor causing concurrent Cushing syndrome and acromegaly.

Dual ectopic secretion of adrenocorticotropic hormone (ACTH) and growth hormone-releasing hormone (GHRH) by a single neuroendocrine tumor (NET) is extremely rare. We report a 43-year-old woman presenting with acral enlargement, weight gain, hyperpigmentation, and proximal muscle weakness. Laboratory evaluation revealed elevated cortisol, ACTH, and insulin-like growth factor 1 (IGF-1), consistent with concurrent Cushing syndrome and acromegaly. Imaging demonstrated a left hilar mass, and biopsy confirmed a pulmonary NET with immunohistochemical (IHC) positivity for synaptophysin and chromogranin. Pituitary magnetic resonance imaging (MRI) showed diffuse hyperplasia, suggesting trophic stimulation rather than a primary pituitary adenoma. Surgical resection resulted in normalization of hormone levels, marked clinical improvement, and regression of pituitary enlargement. Although direct histologic confirmation of tumor-derived GHRH was unavailable, the reversible pituitary hyperplasia favors ectopic GHRH-mediated stimulation rather than primary ectopic GH secretion. IHC of the resected tumor demonstrated ACTH positivity, supporting ectopic ACTH secretion. This case highlights the importance of recognizing dual hormone-secreting NETs in patients presenting with overlapping endocrine syndromes, as early detection and complete resection can lead to remission.