Context: GHRH excess from extracranial endocrine tumors is known to cause somatotroph hyperplasia and acromegaly. Hypothalamic gangliocytomas producing GHRH are also known to be associated with pituitary adenomas causing acromegaly.

Objectives: To describe a case of acromegaly due to a pulmonary GHRH-secreting endocrine carcinoma with metastasis to the pituitary gland and to look at the peculiar histological features of this case.

Subject: The patient was a 44-year-old woman who was diagnosed with biopsy-proven metastatic pulmonary endocrine tumor during pregnancy. Following delivery, she underwent radiation and chemotherapy for pulmonary and skeletal metastases. Her disease was clinically stable for seven years until she developed bitemporal hemianopia. She had symptoms and signs of acromegaly.

Methods: Imaging, biochemical and histological studies were performed.

Results: MRI of the brain confirmed the presence of a 2.6-cm lesion within the sella turcica extending above the sella and compressing the optic chiasm. Endocrine studies showed elevated serum levels of growth hormone, prolactin, -subunit of glycoprotein hormones, insulin-like growth factor-1, chromogranin A and GHRH. The patient underwent uneventful transsphenoidal resection of the sellar tumor. Postoperatively, she noted an improvement in symptoms of acromegaly. Histological examination confirmed metastatic endocrine carcinoma to the pituitary, and immunohistochemistry localized GHRH to the tumor cells. The adjacent pituitary exhibited somatotroph hyperplasia with abundant reactivity for GH and -subunit. In addition, there was focal neoplastic transformation to a sparsely granulated somatotroph phenotype with fibrous bodies.

Conclusion: This is the first report of a GHRH-producing endocrine tumor metastasizing to the pituitary and causing local hyperstimulation with somatotroph hyperplasia and adenomatous transformation.