Growth hormone excess of unknown origin
Falinska A; Ling Y; Tanday R; Vakilgilani, T; Todd JF
Imperial Centre for Endocrinology, Imperial College Healthcare NHS Trust , Hammersmith Hospital, Du Cane Road , London UK
A 68 year old patient was noted to have prognathism, broad fingers and toes and coarse facial features during her admission for a hip replacement 2 years ago. Her family noted change to her facial features and she admitted to increase in her shoe size over 10 years. Her past medical history included treated hypertension only. Her oral glucose tolerance test (OGTT) confirmed paradoxical rise of growth hormone (GH) with peak 6.23mcg/L. Her initial IGF-1 was raised at 131nmol/L (6-30nmol/L) with normal remaining pituitary function. Her initial MRI showed a normal anterior pituitary, 8mm lesion in superior-posterior pituitary elevating the pituitary stalk and infundibulum and an incidental finding of sphenoid wing meningiomas. She was referred for transpehnoidal hypophysectomy. The histology showed fibrosis with no evidence of an adenoma.
However her growth hormone burden remained unchanged postoperatively. Post-surgical IGF-1 was 114nmol/L (6-30nmol/L) and again she failed to suppress GH during OGTT. Ga68 DOTATATE PET CT showed no obvious source of ectopic GH or ectopic GH releasing hormone (GHRH). There was increased uptake within the meningioma which is an expected phenomenon. In addition it demonstrated an 8 mm nodule adjacent to the right lung hilum which was investigated further with high resolution CT and confirmed static nodule with a plan to repeat imaging in one year. Repeated CT brain and two brain MRIs confirmed that the posterior- superior pituitary lesion has been excised and the presence of an unchanged 2 meningiomas but did not reveal any new suspicious lesions within pituitary. She was discussed at local pituitary MDT and the decision was to treat her with somatostatin analogues for one year and re-assess.
This patient GH burden could be due to hidden source in pituitary gland or due to ectopic source. Acromegaly caused by either ectopic GHRH or ectopic GH-producing tumours is very rare accounting for <1% of the cases. Its recognition is clinically important as different therapeutic approaches are required.