What is the workup for acromegaly?

Workup for Acromegaly

The definitive workup for acromegaly includes biochemical testing with insulin-like growth factor I (IGF-I) measurement and an oral glucose tolerance test (OGTT) to assess growth hormone (GH) suppression, followed by pituitary imaging. 1

Initial Biochemical Testing

• Measure serum IGF-I levels, which should be elevated in acromegaly and correlate with clinical features and disease severity 1, 2
• Perform an oral glucose tolerance test (OGTT) with 75g glucose load and measure GH levels at baseline and over 2 hours 1, 3
• Using modern sensitive assays, failure to suppress GH to <1 μg/L during OGTT confirms acromegaly 4, 1
• Random GH <0.4 μg/L and normal age/gender-matched IGF-I levels exclude acromegaly; if either is abnormal, proceed with OGTT 3

Imaging Studies

• Once biochemical diagnosis is confirmed, perform magnetic resonance imaging (MRI) of the pituitary to identify and characterize the adenoma 2, 5
• MRI should assess tumor size, location, and relationship to surrounding structures, particularly optic chiasm and cavernous sinuses 2
• In rare cases where no pituitary adenoma is identified, consider imaging to look for ectopic growth hormone-releasing hormone (GHRH) secretion 2

Assessment of Disease Complications

• Echocardiography to evaluate for cardiac hypertrophy and dysfunction, as heart failure is the most common cause of death in untreated acromegaly 1, 2
• Sleep apnea testing due to high prevalence of sleep-disordered breathing 2
• Metabolic evaluation including glucose tolerance test (separate from diagnostic OGTT) to assess for diabetes 5
• Rheumatologic assessment for joint involvement and arthropathy 2
• Visual field testing if tumor is compressing the optic chiasm 5

Important Considerations

• There may be discordance between GH and IGF-I levels in approximately 15% of patients, so both tests are important for diagnosis 3
• The clinical significance of slightly elevated IGF-I levels remains to be established 4, 1
• Early diagnosis is critical as prolonged exposure to excess GH/IGF-I leads to progressive somatic disfigurement and systemic manifestations associated with increased mortality 2, 5
• Diagnosis is often delayed by 4-10 years after disease onset due to insidious progression of symptoms 2

Common Pitfalls

• Relying solely on random GH measurements is inadequate; OGTT with GH suppression testing is essential 1, 3
• Failure to use age and gender-specific reference ranges for IGF-I can lead to misdiagnosis 3
• Not recognizing that modern, sensitive GH assays require different cut-off values than older assays 4
• Overlooking the need for comprehensive evaluation of comorbidities that determine prognosis 2, 5