Growth hormone-releasing hormone, growth hormone, and neuroendocrine tumors

Neuroendocrine tumors (NETs) are known to produce growth hormone (GH) and growth hormone-releasing hormone (GHRH) leading to acromegaly. Ectopic production of these hormones can lead to ectopic acromegaly which is very rare. Ectopic acromegaly secondary to GHRH has been studied more extensively than GH-related ectopic acromegaly. Given the extreme rarity of these neoplasms, comprehensive guidelines for diagnosis and management of these NETs are currently lacking. This review summarizes the literature on clinical presentation, challenges in diagnosis and management of these NETs. The diagnosis of ectopic acromegaly is often difficult as clinical features do not differ from eutopic acromegaly, and we discuss herein when the clinical suspicion should be held high. GHRH serum concentrations are a useful diagnostic tool when ectopic production is suspected. Once the ectopic source is identified using imaging modalities including advanced molecular imaging, the choice of treatment is surgical resection of the respective NET. Other therapies include use of somatostatin receptor analogues and chemo- or immuno-therapies as an adjunct or in refractory cases.