Acromegaly is caused by a primary growth hormone-secreting pituitary adenoma in more than 95% of the cases. In a small number of patients, it is the result of hypersecretion of growth hormone-releasing hormone (GHRH). Clinical and laboratory findings are similar in both conditions, and the diagnosis of a GHRH-secreting tumor is possible only by identification of GHRH in the tumor or circulation. We report the case of a 61-year-old woman referred to the Hospital Naval Marcílio Dias to investigate a pulmonary mass. The mass was large and calcified, suggesting a hamartoma. The patient also had acromegalic features, elevated serum insulin-like growth factor-1 (IGF-1) levels, and no GH suppression after an oral glucose tolerance test. Magnetic resonance imaging (MRI) showed a diffusely enlarged pituitary gland, suggestive of hyperplasia. The hypothesis of acromegaly secondary to ectopic GHRH secretion by the pulmonary mass was made. A left pneumectomy was performed and histopathologic analysis revealed a carcinoid tumor. A fragment of the tumor was sent for special stains and GHRH was identified by immunohistochemistry. The clinical and biochemical aspects of acromegaly improved 2 weeks after surgery. One year later, serum GH and IGF-1 levels were normal and MRI revealed a partial empty sella. The differential diagnosis of somatotroph adenoma and ectopic GHRH hypersecretion is difficult but is essential to appropriate therapy.
Acromegaly is a rare disease caused by a primary growth hormone-secreting pituitary adenoma (classic acromegaly) in the large majority of the cases. 1 Less than 5% of cases are caused by eutopic tumors (hypothalamic gangliocytomas, hamartomas, and gliomas) or ectopic tumors (carcinoid tumors, pancreatic endocrine tumors, adrenal adenoma, small-cell lung cancer, and pheochromocytoma) secreting growth hormone-releasing hormone (GHRH). This condition is termed ectopic acromegaly. 2 In addition, acromegaly caused by ectopic 6H hypersecretion is extremely rare. 3
We report a patient with acromegaly resulting from ectopic GHRH secretion by a pulmonary carcinoid tumor.