Diagnosis and Treatment > Investigation > GHRH

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Shinichiro Teramoto Department of Neurosurgery, Juntendo University School of Medicine, Tokyo, Japan

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Yuichi Tange Department of Neurosurgery, Juntendo University School of Medicine, Tokyo, Japan

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Hisato Ishii Department of Neurosurgery, Juntendo University Urayasu Hospital, Chiba, Japan

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Hiromasa Goto Department of Metabolism and Endocrinology, Juntendo University School of Medicine, Tokyo, Japan

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Ikuko Ogino Department of Neurosurgery, Juntendo University School of Medicine, Tokyo, Japan

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Hajime Arai Department of Neurosurgery, Juntendo University School of Medicine, Tokyo, Japan

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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:

  • 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.

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Nikolaos Kyriakakis Leeds Centre for Diabetes and Endocrinology, St James’s University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK

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Jacqueline Trouillas Centre de Pathologie Est, Hospices Civils de Lyon, Groupement Hospitalier Est, University of Lyon, Lyon, France

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Mary N Dang Endocrinology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK

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Julie Lynch Leeds Centre for Diabetes and Endocrinology, St James’s University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK

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Paul Belchetz Leeds Centre for Diabetes and Endocrinology, St James’s University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK

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Márta Korbonits Endocrinology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK

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Robert D Murray Leeds Centre for Diabetes and Endocrinology, St James’s University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK

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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:

  • Ectopic acromegaly is rare, accounting for less than 1% of all cases of acromegaly.

  • Ectopic acromegaly is almost always due to extra-pituitary GHRH secretion, mainly from neuroendocrine tumours of pancreatic or bronchial origin.

  • Differentiating between acromegaly of pituitary origin and ectopic acromegaly can cause diagnostic challenges due to similarities in clinical presentation and biochemistry.

  • Serum GHRH can be a useful diagnostic tool to diagnose ectopic acromegaly.

  • Pituitary imaging is crucial to differentiate between a pituitary adenoma and pituitary hyperplasia, which is a common finding in ectopic acromegaly.

  • Diagnosing ectopic acromegaly is pivotal to avoid unnecessary interventions to the pituitary and preserve normal pituitary function.

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