Acromegaly with negative pituitary MRI and no evidence of ectopic source: the role of transphenoidal pituitary exploration?

Growth hormone (GH) producing adenomas of the pituitary gland are usually macroadenomas (>10 mm in size). Often these adenomas are locally invasive by the time of diagnosis. Acromegaly secondary to a very small pituitary microadenoma not visualized on pituitary magnetic resonance (MR) imaging is rare. We report a patient with acromegaly and an unremarkable pituitary MR imaging who had negative work up for ectopic growth hormone-releasing hormone (GHRH) or GH secreting tumors. Transsphenoidal pituitary exploration revealed a pituitary adenoma located on the left side of the sella against the medial wall of the cavernous sinus extending posteriorly along the floor of the sella all the way to the right side. The acromegaly was treated with resection of the pituitary adenoma and normalization of serum insulin-like growth factor 1 (IGF-1) and GH levels. In a patient with acromegaly and unremarkable pituitary MR imaging, with no evidence of ectopic GH and GHRH production, transsphenoidal pituitary exploration is a reasonable approach and may result in clinical improvement and biochemical cure in the hand of experienced surgeon. This approach may avoid long term medical treatment with its associated cost.