Investigations of acromegaly

The investigations in acromegaly should include:

• insulin-like growth factor 1 levels:
  • a better test than growth hormone levels because IGF-1 levels are less variable
  • also raised in pregnancy and puberty
    
    
• failure of growth hormone to be suppressed by 75 g oral glucose - false positive tests occur in poorly controlled diabetes mellitus, anorexia nervosa, hypothyroidism, Cushing's
  
  
• MRI / CT scan may reveal pituitary adenoma
  
  
• chest and abdominal radiology:
  • to detect an ectopic source of growth hormone
  • may detect cardiomegaly due to cardiomyopathy
    
    
• hands radiology reveals:
  • tufting of terminal phalanges
  • increased joint spaces due to cartilage hypertrophy
    
    
• assessment of pituitary function
  
  
• calcium - hypercalciuria is common in acromegaly due to a direct renal tubular action of growth hormone; if there is moderate or severe hypercalcaemia then this is suggestive of hyperparathyroidism (MEN-I)
  
  
• phosphate is often raised

Note that isolated GH measurement may show raised levels - however random levels are not diagnostic because levels vary with the time of day and other factors.