Phaeochromocytoma and Acromegaly: a unifying diagnosis

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.