Abstract Disclosure: I. Yaseen: None. C. Woods: None. D.B. O'Shea: None. R.K. Crowley: None. D. O'Toole: None. H. Almeamar: None. We present a rare case of an ectopic Growth Hormone Releasing Hormone (GHRH)-secreting pulmonary neoplasm manifesting with acromegaly. A 62-year-old woman presented with Bell’s palsy. An incidental lung mass proved to be a 17.5cm carcinoid tumor, DOTATOC-avid, with bony and liver metastases, Ki67 1% on lung and bone biopsy. After pulmonary service referral to endocrinology, she was noted to have acromegalic features, the most troubling of which was macroglossia associated with mouth ulceration. IGF1 was 549ug/L (57-186), random growth hormone was 225. GHRH in serum was 1937ng/ml (reference < 60). MR Pituitary revealed hyperplasia.The multidisciplinary team discussion was that the lung lesion was unresectable, therefore she was commenced on somatuline autogel 120mg every 28 days and an opinion requested re suitability for Peptide Receptor Radionuclide Therapy. After 6 months of therapy IGF1 normalised to 90ug /L. GHRH reduced to 1056ng/L.Imaging at 8 months showed stability of lung primary and bone / liver metastases, with no benefit likely from PRRT at this time. This case highlights the importance of considering endocrine syndromes in the setting of a lung mass. The prevalence of acromegaly in Ireland is 69 per million people; this is the second Irish case known of GHRH-associated GH excess. Ectopic GH-secreting pulmonary tumors are a rare but important differential in patients presenting with acromegalic features. Complete surgical resection can be curative, underlining the significance of a multidisciplinary approach in management, encompassing endocrinology, thoracic surgery, and pathology. This case of successful medical management adds to the limited literature on such tumors and underscores the potential for non-pituitary neoplasms to cause systemic endocrinopathies. Presentation: 6/1/2024