This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders of pituitary gland, Subject name: Medicine
Which is the screening test for acromegaly? 
Select and explain. 
A. Serum IGF-2, B. Oral glucose tolerance test, C. GH levels, D. Serum IGF-1
D: Serum IGF-1
Answer: D: Serum IGF-1 
Explanation: The screening test for acromegaly is Serum IGF-1 levels. IGF-2 is responsible for prenatal growth. Oral glucose tolerance test with GH obtained at 0, 30 and 60 minutes. Normal people can supress growth hormone to <1g/L. Due to pulsatile nature of GH secretion, measurement of a single random value is not useful for diagnosis or exclusion of acromegaly.