Clinical Overview > Hormone > GHRH
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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:
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Sellar gangliocytoma coexisting with pituitary adenoma is recognized as a mixed gangliocytoma-pituitary adenoma and is very rare.
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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.
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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.
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Summary
A male patient presented at the age of 30 with classic clinical features of acromegaly and was found to have elevated growth hormone levels, not suppressing during an oral glucose tolerance test. His acromegaly was originally considered to be of pituitary origin, based on a CT scan, which was interpreted as showing a pituitary macroadenoma. Despite two trans-sphenoidal surgeries, cranial radiotherapy and periods of treatment with bromocriptine and octreotide, his acromegaly remained active clinically and biochemically. A lung mass was discovered incidentally on a chest X-ray performed as part of a routine pre-assessment for spinal surgery 5 years following the initial presentation. This was confirmed to be a bronchial carcinoid tumour, which was strongly positive for growth hormone-releasing hormone (GHRH) and somatostatin receptor type 2 by immunohistochemistry. The re-examination of the pituitary specimens asserted the diagnosis of pituitary GH hyperplasia. Complete resolution of the patient’s acromegaly was achieved following right lower and middle lobectomy. Seventeen years following the successful resection of the bronchial carcinoid tumour the patient remains under annual endocrine follow-up for monitoring of the hypopituitarism he developed after the original interventions to his pituitary gland, while there has been no evidence of active acromegaly or recurrence of the carcinoid tumour. Ectopic acromegaly is extremely rare, accounting for <1% of all cases of acromegaly. Our case highlights the diagnostic challenges differentiating between ectopic acromegaly and acromegaly of pituitary origin and emphasises the importance of avoiding unnecessary pituitary surgery and radiotherapy. The role of laboratory investigations, imaging and histology as diagnostic tools is discussed.
Learning points:
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Ectopic acromegaly is rare, accounting for less than 1% of all cases of acromegaly.
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Ectopic acromegaly is almost always due to extra-pituitary GHRH secretion, mainly from neuroendocrine tumours of pancreatic or bronchial origin.
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Differentiating between acromegaly of pituitary origin and ectopic acromegaly can cause diagnostic challenges due to similarities in clinical presentation and biochemistry.
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Serum GHRH can be a useful diagnostic tool to diagnose ectopic acromegaly.
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Pituitary imaging is crucial to differentiate between a pituitary adenoma and pituitary hyperplasia, which is a common finding in ectopic acromegaly.
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Diagnosing ectopic acromegaly is pivotal to avoid unnecessary interventions to the pituitary and preserve normal pituitary function.
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Sackler School of Medicine, Tel-Aviv University, Tel Aviv, 69978, Israel
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Sackler School of Medicine, Tel-Aviv University, Tel Aviv, 69978, Israel
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Search for other papers by Hilla Knobler in
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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
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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.
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Detection of GHRH in the blood and in the tumor-derived medium supports the diagnosis of ectopic GHRH secretion.
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Functional bioactivity of pNET-secreted GHRH can be proved in vitro by releasing GH from human pituitary cells.
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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
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Incidental findings on imaging require thorough investigation to determine the presence of serious pathology.
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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.
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Acromegaly is due to ectopic GHRH-secreting neuroendocrine tumours in <1% of cases, most commonly pancreatic or bronchial lesions.
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Co-secretion of GHRH from a phaeochromocytoma is extremely rare.
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In such cases, the pituitary gland may appear enlarged but pituitary surgery should be avoided and surgical treatment of the neuroendocrine tumour attempted.
