Endocrine Abstracts

Introduction: Pituitary incidentaloma (PitInc), defined as an unsuspected mass observed on imaging studies performed for unrelated conditions. Most such lesions are not clinically significant at initial evaluation and current guidelines recommend periodic follow-up.

Aim: To present a rare case of delayed onset of acromegaly in a patient with a nonfunctioning PitInc, raising the question of the utility of prolonged follow-up of PitInc.

Methods: Clinical examination, biochemical and imaging studies.

Case report: Following a contrast head CT for headache, a 63 years old female presented with a 11×5 mm intrasellar pituitary mass, no clinical signs of pituitary hypersecretion and normal serum prolactin and IGF-I. Subsequent follow-up showed non-progression of mass size on CT/MRI and normal prolactin/IGF-I. 10 years from initial diagnostic, unexplained hyperkalemia prompted re-evaluation, revealing mild skin hyperpigmentation, absence of other signs of adrenal failure, a small increase in shoe size, without other acromegalic features. IGF-I was high (2.2-2.9 xULN), the GH nadir during OGTT was diagnostic for acromegaly. Review of MRI scans revealed a minimal lesion size progression and cystic changes. Visual fields were normal. The patient was offered surgery but chose to start cabergoline, dose-titrated to 3 mg/week, leading to IGF-I normalization. ACTH was elevated and increased progressively, 8 AM serum cortisol was normal, with subnormal response to Synacthen, suggesting subclinical primary adrenocortical failure. An adrenal CT scan excluded adrenal masses, but revealed a discrete left adrenal non-nodular hyperplasia. Serum 17 HO-progesterone was elevated, suggesting concomitant congenital adrenal hyperplasia. The patient is clinically well on glucocorticoid and mineralocorticoid replacement and hyperkaliemia resolved.

Conclusions: The current PitInc guideline (Endocrine Society 2011) does not specify a maximum follow-up period. Prolonged clinical and hormonal evaluation may be warranted, as delayed onset endocrine disease can occur. In our case, incidental hyperkalemia prompted endocrine re-evaluation revealing multiple endocrine abnormalities.