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Open access

Shinichiro Teramoto, Yuichi Tange, Hisato Ishii, Hiromasa Goto, Ikuko Ogino and Hajime Arai

Summary

A 67-year-old woman with a past history of type 2 diabetes mellitus presented with worsening glycemic control. She had some acromegaly symptoms and magnetic resonance imaging demonstrated a pituitary tumor. Endocrinological examination found the resting growth hormone (GH) level within the normal range, but elevated insulin-like growth factor 1 level. A 75 g oral glucose tolerance test showed inadequate suppression of nadir GH levels. Acromegaly due to GH-secreting pituitary tumor was diagnosed. The patient underwent endoscopic transsphenoidal surgery resulting in gross total removal of the tumor and recovered well postoperatively. Histological examination of the tumor showed coexistence of relatively large gangliocytoma cells and pituitary adenoma cells, suggesting mixed gangliocytoma-pituitary adenoma. In addition, colocalization of GH and GH-releasing hormone (GHRH) in pituitary adenoma cells was revealed, so the adenomatous components were more likely to produce GHRH in our mixed gangliocytoma-pituitary adenoma case. Mixed gangliocytoma-pituitary adenoma is very rare, and the present unique case demonstrated only the adenomatous components associated with GHRH production.

Learning points:

  • Sellar gangliocytoma coexisting with pituitary adenoma is recognized as a mixed gangliocytoma-pituitary adenoma and is very rare.
  • A proposed developmental mechanism of growth hormone (GH)-secreting mixed gangliocytoma-pituitary adenoma involves GH-releasing hormone (GHRH) produced by the gangliocytic components promoting the growth of tumor including GH-secreting adenomatous components.
  • Since our present case indicated that the adenomatous components of mixed gangliocytoma-pituitary adenoma could secrete both GH and GHRH simultaneously, progression of GH-secreting mixed gangliocytoma and pituitary adenoma may involve exposure to spontaneously produced GHRH due to the adenomatous components.
Open access

Taiba Zornitzki, Hadara Rubinfeld, Lyudmila Lysyy, Tal Schiller, Véronique Raverot, Ilan Shimon and Hilla Knobler

Summary

Acromegaly due to ectopic GHRH secretion from a neuroendocrine tumor (NET) is rare and comprises <1% of all acromegaly cases. Herein we present a 57-year-old woman with clinical and biochemical features of acromegaly and a 6 cm pancreatic NET (pNET), secreting GHRH and calcitonin. Following surgical resection of the pancreatic tumor, IGF1, GH and calcitonin normalized, and the clinical features of acromegaly improved. In vitro studies confirmed that the tumor secreted large amounts of both GHRH and calcitonin, and incubation of pNET culture-derived conditioned media stimulated GH release from a cultured human pituitary adenoma. This is a unique case of pNET secreting both GHRH and calcitonin. The ability of the pNET-derived medium to stimulate in vitro GH release from a human pituitary-cell culture, combined with the clinical and hormonal remission following tumor resection, confirmed the ectopic source of acromegaly in this patient.

Learning points

  • Signs, symptoms and initial work-up of acromegaly due to ectopic GHRH secretion are similar to pituitary-dependent acromegaly. However, if no identifiable pituitary lesion is found, somatostatin receptor scan and further imaging (CT, MRI) should be performed.
  • Detection of GHRH in the blood and in the tumor-derived medium supports the diagnosis of ectopic GHRH secretion.
  • Functional bioactivity of pNET-secreted GHRH can be proved in vitro by releasing GH from human pituitary cells.

Open access

C Mumby, J R E Davis, J Trouillas and C E Higham

Summary

A 52-year-old lady was referred after a 5 cm left adrenal mass was detected on computed tomography (CT) scanning. She was asymptomatic although was noted to have acromegalic facies. Blood pressure (BP) was normal but plasma normetanephrines were raised to 2.81 mmol/l (<1.09) and urinary normetadrenaline excretion 5.3 μmol/24 h (0–4.3). Adrenal biochemistry screen was otherwise normal. Metaiodobenzylguanidine (MIBG) scan demonstrated uptake in the adrenal lesion. Growth hormone (GH) nadir on oral glucose tolerance test (OGTT) was 2.2 ng/ml with an elevated IGF1 level of 435 ng/ml (72–215), confirming acromegaly biochemically. The remainder of the pituitary screen was normal. A magnetic resonance imaging (MRI) scan of the pituitary revealed an enlarged pituitary gland with a microadenoma/cyst of 2–3 mm in diameter. Alpha blockade was achieved with a titrated dose of phenoxybenzamine before a successful laparoscopic hand-assisted left adrenalectomy. Postoperative biochemical testing revealed a normal plasma normetanephrine level of 0.6 nmol/l (<1.09) and a metanephrine level of 0.35 nmol/l (<0.46 nmol/l). Nadir on OGTT was normal at 0.07 ng/ml with an IGF1 level within the reference range at 111 ng/ml (75–215). Histology demonstrated a well-circumscribed and encapsulated oval mass with microscopic features typical for a phaeochromocytoma. The sections stained strongly positive for GHRH in 20% of cells on immunocytochemistry. Genetic analysis showed no pathogenic mutation. This is a report of the rare condition of a phaeochromocytoma co-secreting GHRH resulting in clinical and biochemical acromegaly. Neuroendocrine tumours can stain positive for GHRH without coexisting acromegaly, but the resolution of patient symptoms and normalisation of serum GH and IGF1 levels following surgery imply that this was functional secretion. Pituitary surgery should be avoided in such cases.

Learning points

  • Incidental findings on imaging require thorough investigation to determine the presence of serious pathology.
  • Acromegaly and phaeochromocytoma are rarely coincident in the same patient. If this occurs, co-secretion of GHRH from the phaeochromocytoma or the presence of underlying genetic abnormalities must be considered.
  • Acromegaly is due to ectopic GHRH-secreting neuroendocrine tumours in <1% of cases, most commonly pancreatic or bronchial lesions.
  • Co-secretion of GHRH from a phaeochromocytoma is extremely rare.
  • In such cases, the pituitary gland may appear enlarged but pituitary surgery should be avoided and surgical treatment of the neuroendocrine tumour attempted.