Giustina et al developed consensus criteria for evaluating patients for acromegaly. Acromegaly can be excluded based on results of biochemical tests. The authors are from multiple universities in Europe and the United States.
Measures:
(1) random fasting or random growth hormone level
(2) nadir growth hormone during an oral glucose tolerance test (OGTT, 75 gram, with glucose measurements every 30 minutes up to 2 hours)
(3) serum insulin growth factor I (IGF-I) levels
(4) mean integrated 24 hours growth hormone level
Criteria for exclusion of acromegaly using biochemical tests:
(1) random serum growth hormone concentration < 0.4 µg/L AND serum IGF-1 within normal reference range for age and gender
(2) nadir serum growth hormone concentration during the OGTT is < 1.0 µg/L AND serum IGF-1 within normal reference range for age and gender
(3) mean integrated 24-hour growth hormone level < 2.5 µg/L
where:
• The mean integrated 24-hour growth hormone level is usually not performed since the oral glucose tolerance test is more cost effective.
• The oral glucose tolerance test is used to suppress growth hormone release.
The recommended sequence of testing is:
(1) Measure random GH and IGF-1 levels. If both normal then acromegaly is excluded.
(2) If the random GH is elevated, then GH suppression with the oral GTT is performed. If criteria 2 is met then acromegaly is excluded.
(3) If acromegaly is not excluded then additional studies are warranted.
Conditions associated with a failure for growth hormone nadir during OGTT (false positive test):
(1) diabetes mellitus
(2) liver disease
(3) renal disease
(4) adolescence
(5) anorexia nervosa
Occasional patients with acromegaly may show a nadir in the growth hormone to < 1 µg/L during the OGTT, but the IGF-I levels will be elevated and there may be clinical findings suggestive of acromegaly.
Specialty: Endocrinology, Clinical Laboratory
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