Determination of Nadir growth hormone concentration cutoff in patients with acromegaly

Objective: The purpose of this study was to define an appropriate nadir growth hormone (nGH) cutoff for patients with acromegaly in remission using the Access Ultrasensitive human growth hormone (hGH) assay (Beckman Coulter, Brea, CA).Methods: This cross-sectional study included 55 acromegalic subjects and 41 healthy adult volunteers. All subjects underwent oral glucose tolerance testing (OGTT) for growth hormones (GHs). An optimal cutoff for nGH for patients with active disease versus those in remission was determined using receiver-operating curve analysis.Results: The nGH of 0.53 ng/mL revealed a sensitivity of 97% (95% confidence interval [CI], 83-100%) and a specificity of 100% (95% CI, 82-100%). All 22 patients with acromegaly in remission suppressed GH to <1 ng/mL, 20/22 (91%) suppressed to <0.4 ng/mL, and 19/22 (86%) of subjects suppressed to <0.3 ng/mL (the maximum nGH measured in our healthy volunteer group).Conclusion: When using the Access Ultrasensitive hGH assay for OGTT, a cutoff of 0.53 ng/mL was found to most accurately differentiate patients with acromegaly in remission from those with active disease.