A 46-year-old man has headache, increased shoe size, and hypertension. Random growth hormone is 4 ng/mL and IGF-1 is elevated above age-matched norms. Which result confirms the diagnosis of acromegaly?

• A Suppression of GH below 0.5 ng/mL after glucose load
• B A single random GH level above 2 ng/mL
• C Failure of GH to suppress below 1 ng/mL during a 75 g oral glucose tolerance test ✓
• D Blunted prolactin response to TRH stimulation

Explanation

In acromegaly, GH secretion is autonomous and paradoxically fails to suppress, remaining above 1 ng/mL during an oral glucose tolerance test. C random GH value alone is unreliable because GH pulsatility can produce normal values between pulses, so it cannot confirm or exclude disease. Elevated IGF-1 screens for the condition but the glucose-suppression test establishes it.

Reference: Williams Textbook of Endocrinology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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