(13.12) Ectopic Acromegaly: A Rare Presentation of an IGF-1 Producing Typical Carcinoid in the Lung

A 32-year-old male presented with mandibular hyperplasia, macroglossia, and soft tissue enlargement of his hands and feet for several years, concerning for Acromegaly. 

 





Case(s) Description : Labs revealed elevated levels of IGF-1 at 675 ng/ml and 843 ng/ml on repeat testing (normal range: 53-331 ng/ml) and elevated growth hormone (GH) of 26.6 ng/ml (normal range: ≤ 7.6 ng/ml). Brain MRI revealed a 4x3 mm hypoenhancing focus in the posterior region of the pituitary gland, suggestive of a pituitary  microadenoma.   The patient underwent transsphenoidal surgery of the pituitary microadenoma.  However, pathology obtained from the anterior pituitary showed no evidence of a definite adenoma. Furthermore, his IGF-1 levels remained elevated at 894 ng/mL. Additional evaluation with a CT scan found an  8 x 8 cm mass in the right lower lung with internal calcifications, suspicious for a carcinoid tumor. Given the ectopic source, testing for growth hormone releasing hormone (GHRH) was sent and returned elevated at 27 pg/ml (normal 5-18 pg/ml). CT guided lung biopsy confirmed a typical Carcinoid neuroendocrine tumor (grade 1).  Six months after his initial pituitary resection, the patient underwent a right lung lobectomy. Surgical removal of the lung carcinoid resulted in a gradual decline of IGF-1 levels to normal (252 ng/ml) two months later. Follow up GHRH testing also normalized to 7 pg/ml, indicating successful resection of the ectopic source.

Discussion : Acromegaly is a rare condition, with an estimated diagnosis rate of 3-14 cases per 100,000 people. The majority of acromegaly cases are caused by pituitary gland tumors that secrete growth hormone. However, less than 1% of acromegaly cases are manifestations of ectopic tumors that secrete IGF-1 Ectopic carcinoid tumors associated with acromegaly can secrete various hormones, including GH, GHRH, and IGF-1. Lung neuroendocrine tumors (NETs) account for 1-2% of all lung malignancies and approximately 20-30% of NETs. This case emphasizes the importance of considering ectopic sources when treating acromegaly.