Recovery of pituitary function in the late-postoperative phase after pituitary surgery: results of dynamic testing in patients with pituitary disease by insulin tolerance test 3 and 12 months after surgery

The insulin tolerance test (ITT) is considered the gold standard for assessment of GH and ACTH reserve in patients with pituitary disease following pituitary surgery and is usually performed after 6-12 weeks. However, abnormal axes may not be completely recovered by then. The aim of this study was to evaluate dynamic testing 3 and 12 months after transsphenoidal pituitary surgery. Design and patients: Serial dynamic testing was performed in 36 patients (13 women, age 18-78) at 3 and 12 months after transsphenoidal surgery. Results: Compared with 3-month results, median GH peak levels during ITT after 12 months increased by 38% (P < 0.05). In patients initially classified as GH deficiency (GHD), median GH peak increased after 12 months by 23% (P < 0.05). At 3 and 12 months, 36% (13/36) and 47% (17/36) were GH sufficient respectively. Median cortisol peak levels after 12 months increased by 17% (P < 0.01) compared with 3-month ITT. In ACTH-insufficient (AI) patients, peak cortisol levels increased significantly by 12% (P < 0.05) at 12 months, and in ACTH-sufficient patients, peak cortisol levels increased significantly by 13% (P < 0.05). At 12 months, there was recovery from AI in 11% of the patients, and recovery from GHD in 11% of patients. Conclusions: Serial dynamic testing results in a change in classification by ITT results in a relevant proportion of patients. Dynamic testing should be repeated during follow-up.