Silent growth hormone secreting pituitary adenomas: IGF-1 is not sufficient to exclude growth hormone excess.

Circulating insulin-like growth factor-1 (IGF-1) is increasingly being used as a screening test and in ongoing monitoring of treated acromegaly. We here present three cases of women (two of whom were on the oestrogen containing contraceptive pill at the time of presentation) who had normal circulating IGF-1 and no overt clinical features of acromegaly at the time of their pituitary surgery. Postoperatively, all were confirmed to have growth hormone excess in keeping with the presence of active somatotroph pituitary adenomas. We suggest that for optimal patient management, formal evaluation of growth hormone status with oral glucose tolerance testing should ideally be performed on all individuals for whom pituitary surgery is planned.