Subclinical Acromegaly due to a Pituitary Cystic Somatotroph Adenoma

Abstract

Objective: 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. Methods: We report a rare case of subclinical acromegaly that presented as a cystic sellar lesion on magnetic resonance imaging (MRI). Results: 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. Conclusion: 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. Abbreviations: GH = growth hormone; IGF-1 = insulin-like growth factor 1; MRI = magnetic resonance imaging; RCC = Rathke cleft cyst