Recovery rate of adrenal function after surgery in patients with acromegaly is higher than in those with non-functioning pituitary tumors: a large single center study

Purpose: To compare hypothalamus–pituitary–adrenal (HPA) axis integrity at diagnosis and recovery after transsphenoidal surgery (TSS), in acromegaly patients, compared with tumor size matched non-functioning adenoma (NFA) patients. Methods: A retrospective 7-year evaluation of acromegaly patients, who underwent TSS with 52 weeks follow-up at a single institution, was undertaken. 50 acromegaly with complete follow-up data at all points and 50 NFA patients were matched for tumor size; HPA axis was similarly assessed pre-operatively and at 6, 12 and 52 weeks post-operatively. Recovery of HPA axis and gender specific prevalence of adrenal insufficiency (AI), were analyzed in both groups. We also studied AI in acromegaly patients requiring medical therapy post-operatively vs those in remission after surgery. Results: AI remained less prevalent in acromegaly vs NFA (acromegaly, p = 0.01; NFA, p = 0.15) at 52 weeks after surgery, although the prevalence of AI decreased in both groups from baseline by 52 weeks. Additionally, recovery from baseline AI was significantly greater by 52 weeks in acromegaly patients over NFA patients (p = 0.001). Recovery of HPA axis in acromegaly patients remained significant (p = 0.03) despite the need for medical therapy. AI at baseline was proportionately more prevalent in acromegalic males at baseline (p = 0.002) but no gender difference was apparent at 52 weeks (p = 0.35). Conversely, in NFA patients, no gender difference was apparent pre-operatively (p = 0.49), but AI was more prevalent in males at 52 weeks (p = 0.001). Conclusion: In the longest comparative study to date using a standard assessment modality, HPA axis recovery was more frequent in acromegaly compared to NFA patients, independent of tumor size, cavernous sinus invasion (CSI), and body mass index (BMI). HPA axis integrity must be carefully and periodically monitored in acromegaly patients during short- and long-term follow-up to prevent overtreatment with glucocorticoids.