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.