Institutional Protocol for Assessment of Postoperative Hypopituitarism after Endoscopic Transsphenoidal Surgery for Pituitary Adenomas: Importance of Learning Curve on Endocrinological Outcomes

Introduction: One of the major concerns when considering surgical resection of pituitary adenomas is the risk of developing postoperative hypopituitarism requiring long-term hormone replacement therapy (HRT). In general, patients are often pre-emptively placed on postoperative HRT without definitive evidence of hypopituitarism after surgery. This can result in unnecessary HRT and an overestimation of the rate of hypopituitarism in those who have an otherwise normal, functional pituitary gland. With the advent of endoscopic endonasal transsphenoidal surgery (EETS), pituitary adenomas can be removed with higher precision and preservation of the pituitary gland, possibly reducing the need for additional life-long HRT. In the present study, we investigated endocrinological outcomes on patients who underwent EETS for pituitary adenomas, focusing on the incidence of new anterior hypopituitarism (hypocortisolemia and hypothyroidism) and the need for HRT using an institutional protocol.

Materials and Methods: A retrospective chart review was conducted on patients who underwent EETS for pituitary adenoma between December 2009 and May 2015 at our institution. Patient charts were used to collect pre- and post-operative characteristics, hormone laboratory values, and operative and follow-up notes. Ultimately, 101 patients were identified and 20 were excluded because they had preoperative adrenal axis dysfunction, such as pre-existing hypocortisolemia, hypercortisolemia (Cushing’s disease), and pituitary apoplexy. An institutional protocol was implemented postoperatively where HRT was withheld from patients unless they demonstrated anterior hypopituitarism based on biochemical and clinical evidence.

Results: In total, 7 of 81 patients (8.6%) developed new hypopituitarism, specifically hypocortisolemia or hypothyroidism, requiring HRT following EETS for a pituitary adenoma. There did not appear to be any statistically significant correlation between developing new anterior hypopituitarism and tumor size, tumor type (functional versus non-functional), and gender of the patient. The postoperative day 1 serum fasting AM cortisol levels were not significantly different between the new hypopituitarism group and the normal pituitary function group (26.9 versus 38.1 mg/dL, p>0.05). However, the postoperative day 2 serum fasting AM cortisol level in the new hypopituitarism group was significantly lower than in the normal pituitary function group (5.9 versus 19.5 mg/dL, p < 0.05). In addition, the rate of developing new hypopituitarism was significantly higher in the early part of the series (2009–2011) than the later experience (2012–2015) (20.8% versus 3.5%, p < 0.05).

Conclusion: Our strategy of withholding postoperative HRT until there is definitive biochemical and clinical evidence of new anterior hypopituitarism appears to be a safe and useful protocol for determining those who require postoperative HRT. This can avoid unnecessary declaration of hypopituitarism in patients who may have otherwise normal pituitary function. Fasting serum AM cortisol levels obtained on postoperative day 2 appear to be a more useful detector of early hypocortisolism. Furthermore, this study demonstrates the impact of the learning curve and the improvement of endocrinological outcomes with surgeon experience.