Subclinical Acromegaly due to a Pituitary Cystic Somatotroph Adenoma

Abstract

Excess growth hormone (GH) secretion from a cystic sellar lesion is rare. Indeed, there have been few cases of hormone-secreting pituitary adenomas with a cystic component. We report a rare case of subclinical acromegaly that presented as a cystic sellar lesion on magnetic resonance imaging (MRI). A 34-year-old Caucasian female presented with arthralgias, diaphoresis, paresthesias, cognitive slowing, headaches, presyncope, anxiety, and depression. She underwent evaluation by multiple providers without a diagnosis. Her physical examination was reportedly normal without evidence to suggest acromegaly. While she was undergoing workup for multiple sclerosis, a brain MRI scan revealed a cystic sellar lesion measuring approximately 1.6 × 0.9 cm approaching the optic chiasm. An insulin-like growth factor 1 level was incidentally screened months later and was elevated at 823 ng/mL (reference range is 69 to 227 ng/mL). A subsequent oral glucose tolerance test reported a growth hormone level of 7.5 ng/mL at its nadir (reference range is <1.0 ng/mL). Additional assessment of the pituitary axis reported normal levels of prolactin, luteinizing hormone, follicle-stimulating hormone, thyroid-stimulating hormone, free thyroxine, cosyntropin stimulation test, and a normal 24-hour urinary free cortisol collection. The patient underwent transsphenoidal surgery and her pathology reported a somatroph tumor that stained positive for GH and alpha subunit. No postsurgical complications were noted and postoperative MRIs did not demonstrate evidence of tumor recurrence. Cystic pituitary adenomas can secret GH and may present with no classic clinical features of acromegaly. This case emphasizes the importance of a thorough hormonal evaluation in patients who present with a cystic pituitary incidentaloma.