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If you suspect that a patient may have acromegaly, what test should you order?
- The single best screening test for acromegaly is the plasma level of IGF-1. Unlike GH levels, which are pulsatile and higher at night, samples can be drawn any time of day.
- In adults, acromegaly is essentially the only condition that causes elevated IGF-1 levels.
- In children, IGF-1 levels are more difficult to interpret because growing children normally have high levels. IGF-1 levels may be less accurate in mild acromegaly, malnutrition, or hepatic or renal disease.
The patient’s IGF-1 level is not elevated, but you still think that she may have acromegaly. What other test should you order?
- The gold standard test to rule out acromegaly is the measurement of serum GH levels in the fasting state and after glucose suppression.
- Healthy subjects suppress GH levels to < 1 mcg/L 2 hours after an oral glucose load (75 g), whereas patients with acromegaly show insufficient suppression in GH levels.
- This test may be unreliable in patients with diabetes mellitus, hepatic or renal disease, obesity, pregnancy, or in patients receiving estrogen therapy.
