A 42-year-old woman with acromegaly is found to have a GH level of 8 ng/mL after an oral glucose tolerance test (OGTT). Which of the following best explains the failure of glucose suppression?

Explanation

## GH Suppression Test in Acromegaly **Diagnostic Principle:** In healthy individuals, oral glucose load suppresses GH to <1 ng/mL within 30–60 minutes. Failure of suppression (GH >1 ng/mL) is diagnostic of acromegaly. **Key Point:** GH-secreting adenomas produce GH autonomously, independent of normal physiologic feedback mechanisms. Glucose suppression fails because: - The tumor cells are not responsive to glucose-induced somatostatin release - Autonomous hormone secretion overrides normal inhibitory signals - This is pathognomonic for GH-secreting adenoma **Clinical Pearl:** The OGTT is the gold standard confirmatory test for acromegaly. Failure of GH suppression to <1 ng/mL confirms autonomous GH production. **Mnemonic:** **OGTT-GH** = Gold standard for acromegaly diagnosis.