A 44-year-old man has coarse facial features, enlarged hands, and a jaw that has changed dentures twice in three years. IGF-1 level is elevated above the age-matched reference range. Which result on a 75 g oral glucose tolerance test confirms the diagnosis of acromegaly?
- A Failure of growth hormone to fall below 1 ng/mL during the test ✓
- B Growth hormone rising more than twofold from baseline
- C Failure of growth hormone to rise above 5 ng/mL at any point
- D Two-hour glucose exceeding 200 mg/dL regardless of growth hormone values
Correct answer: A. Failure of growth hormone to fall below 1 ng/mL during the test
Explanation
In healthy subjects oral glucose suppresses growth hormone to less than 1 ng/mL (less than 0.4 ng/mL with ultrasensitive assays). Failure to suppress below this threshold, together with a raised age-adjusted IGF-1, establishes acromegaly. Glucose paradoxically may not suppress GH in acromegalics; diabetes mellitus occurs commonly but glucose values alone do not confirm the diagnosis.
Reference: Williams Textbook of Endocrinology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.