Endocrine Abstracts

Acromegaly secondary to ectopic growth hormone-releasing hormone (GHRH) is rare accounting for less than 1% of cases of acromegaly. Less than 100 cases have been reported in the literature mainly as case reports, except for a nationwide French series of 21 cases. Ectopic acromegaly occurs more frequently in women who represent 2/3 of cases. Median age at diagnosis is 41 years but ranges from adolescence to elderly. GHRH secreting neuroendocrine tumors are usually well differentiated, originating in 90% of cases from pancreas or lung. Pheochromocytomas or paragangliomas have been reported in a small proportion of cases. Positive immunoexpression for GHRH is found in most tumors. Clinical and hormonal features of ectopic acromegaly are very similar to that of somatotropic adenomas and differentiating between both may be challenging. Pituitary may be normal or enlarged at MRI which may be difficult to interpret especially in MEN1 patients where the association of a microprolactinoma to a pancreatic tumor secreting GHRH may be misleading. GHRH plasmatic measurement has an excellent specificity for the diagnosis. Tumors are usually large and easy to localize by conventional imaging or somatostatin receptor scintigraphy. Prognosis is usually favorable, even in metastatic forms which represent 50% of cases. Surgical approach is recommended and, when a complete tumoral resection is feasible, results, in most patients, in long-lasting remission. In such cases, GHRH concentration is normalized and its increase is an accurate indicator of recurrence. In uncured patients, somatostatin analogs control GH secretion but inhibit, only partially, GHRH secretion. MEN1 mutation should be systematically investigated in patients with a pancreatic tumor.