Most cases of acromegaly are due to pituitary somatotroph adenomas, however a minority (<2%) of cases are due to GHRH hypersecretion (1). Mixed pituitary adenoma and gangliocytoma tumours are rare, and less than 80 cases are described in the literature (2). Most intra-pituitary gangliocytomas are associated with hormonal hypersecretion, commonly growth hormone (GH) excess (2). We report a case of acromegaly secondary to a mixed pituitary adenoma-gangliocytoma, and discuss the possibility of ectopic GHRH secretion from gangliocytomas.
A 60 year old male was referred for assessment of a pituitary mass found following investigation of chronic headaches over the preceding two years. MRI head revealed a 1.9 x 1.7 x 2.4cm right sided pituitary macroadenoma with invasion into the right cavernous sinus but no compression of the optic chiasm.
Examination findings were consistent with acromegalic features. He had no other symptoms or signs of endocrine dysfunction, nor family history of endocrinopathies. Static pituitary hormone testing showed an elevated IGF-1 122 nmol/L and elevated GH 5.2 ug/L. The remaining pituitary hormonal profile was normal. His GH failed to suppress following an oral glucose tolerance test (OGTT) (GH nadir 3.1 ug/L).
He underwent uncomplicated endoscopic trans-sphenoidal resection of the mass. Histopathology revealed a gangliocytoma (composite chromophobe pituitary adenoma and ganglion cells in neutropil). Immunohistochemistry of adenoma cells stained weakly for GH. Immunostaining for GHRH has been requested. An ultra-early (day 2) post-operative OGTT demonstrated suppression of GH to <1ng/ml. This will be repeated at 8-12 weeks post-operative.
In conclusion, we report an uncommon case of a mixed pituitary adenoma-gangliocytoma causing acromegaly. We hypothesise that ganglion cells secrete GHRH, subsequently inducing GH secretion from the adenoma cells. We review the literature to see if these lesions behave differently to classic acromegaly.