Endocrine Abstracts

Case History: A 35-year-old was referred to surgery with a confirmed diagnosis of symptomatic acromegaly. Her GH failed to suppress during an oral glucose tolerance test (OGTT), her IGF-1 and prolactin was high. The histology and immunocytochemistry suggested pituitary hyperplasia. We started to look for conditions associated with pituitary hyperplasia resulting in GHRH production, including the genetic tests for inherited conditions. A solitary nodule was noted in her neck during an examination.

Investigations: She had an ultrasound scan guided fine needle aspiration of the thyroid nodule, and cytology was Thy3f nodule. Her calcitonin level was normal. She had an NMGa68DOTATATE whole body PET CT and this showed a large DOTATATE avid mass from the right adrenal gland compatible with Pheochromocytoma. Her 24 hours total urinary metadrenaline and normetadrenaline was high. Her genetic test for MEN1, CDKN1B, and MEN2 are negative. Her GHRH was markedly high.

Treatment: She had adrenalectomy for pheochromocytoma and remains very well.

Conclusions and points for discussion: Acromegaly is rarely due to an excess of the GH-releasing hormone (GHRH). Ectopic GHRH secretion accounts for <1% of cases of Acromegaly. It is most commonly secondary to gastropancreatic neuroendocrine tumours and bronchial carcinoid tumours. Dynamic pituitary tests are not helpful in distinguishing acromegalic patients with pituitary tumours from those harbouring extra pituitary tumours. When a GHRH secreting tumour is not identified, then the possibility of an underlying genetic syndrome such as MEN1/MEN4, Carney Complex, McCune Albright and X-linked acrogigantism syndrome should be considered. The distinction of pituitary vs extrapituitary Acromegaly is important in planning management. Surgical resection of the tumour secreting ectopic GHRH if possible is the treatment of choice in a patient with the ectopic GHRH syndrome Ectopic GHRH acromegaly should be suspected in a patient with biochemical/clinical features of acromegaly in the presence of co-existing neuroendocrine tumours, or if there is resolution of acromegaly after the surgical resection of the primary neuroendocrine tumour when there is diffuse pituitary enlargement on imaging and persistent acromegaly after surgery if there is histological evidence of somatotroph hyperplasia. Plasma GHRH levels are usually elevated in patients with peripheral GHRH-secreting tumours and are normal or low in patients with pituitary acromegaly