The structure of growth hormone releasing hormone (GHRH) was first discovered when it was extracted from the pancreatic tissue of a person with acromegaly. Release of this hormone stimulates the pituitary to release excessive amounts of growth hormone (GH) that causes gigantism or acromegaly. These tumours are more commonly seen in patients with MEN 1, and secrete the 40 amino acid form of GHRH, compared to the 44 amino acid released by the hypothalamus.
While GHRH has been found in up to 25% of pancreatic islet cell tumours, gigantism and acromegaly are rarely seen as a result. The high levels of GHRH may only induce an excessive release of GH if there is also a tumour in the pituitary facilitating the increased secretion of GH. Therefore, the diagnosis of a pancreatic GHRHoma rests on detection of raised levels of GHRH, and not GH.
Surgery provides the best chance of a cure. In patients with acromegaly, the removal of the tumour will cure the acromegaly or gigantism.
GHRHomas not associated with MEN 1 contain large numbers of somatostatin receptors. They can be treated successfully with octreotide, a somatostatin analogue that will inhibit the release of GHRH in patients with unresectable tumours.