Diagnosis and Management of Acromegaly

Initial Screening and Diagnosis

The diagnosis of acromegaly requires measuring serum IGF-I levels as the initial screening test, followed by an oral glucose tolerance test (OGTT) with GH measurement, where failure to suppress GH to <1 μg/L during OGTT confirms the diagnosis, as recommended by clinical guidelines 1
Measure serum IGF-I levels as the first-line screening test when acromegaly is clinically suspected, using age-specific, sex-specific, and (in adolescents) Tanner stage-specific reference ranges 1
An elevated IGF-I level warrants confirmatory testing with OGTT, which is the gold standard diagnostic test for acromegaly 1

Normal individuals suppress GH to <1 μg/L during OGTT using modern sensitive assays, and failure to suppress GH to this level confirms acromegaly 1
With ultrasensitive assays, the suppression cutoff may be as low as 0.4 μg/L, and both GH and IGF-I must be evaluated together at baseline and during follow-up 1
Discordant results between GH and IGF-I require careful clinical correlation, as IGF-I correlates linearly with GH only up to 4 μg/L, then plateaus around 10 μg/L 2, 3

Suspect acromegaly in patients presenting with systemic manifestations such as joint pain, headache, excessive sweating, visual field defects, and cardiovascular complications like hypertension and left ventricular hypertrophy 4, 5
In children and young people, test for GH excess when there is height >2 standard deviation scores (SDS) above age-adjusted and sex-adjusted norms, or persistently elevated growth velocity (>2 SDS) with acromegalic features 4

Contrast-enhanced pituitary MRI is essential after biochemical confirmation to identify and characterize the pituitary adenoma, and to assess tumor volume, extension, and relationship to surrounding structures 4
Once acromegaly is diagnosed, evaluate for cardiovascular complications like left ventricular hypertrophy and valvular disease using echocardiography, and for sleep apnea using polysomnography or sleep study 5
Metabolic complications like diabetes mellitus should be evaluated using glucose tolerance testing, and colonoscopy should be performed starting at age 40 due to increased colorectal neoplasia risk 1, 5

Do NOT use GH suppression during OGTT for monitoring patients on medical therapy, as results are inconsistent and unreliable in this setting, and ensure proper assay selection and interpretation using method-specific reference ranges 1, 2, 3, 6, 7