growth hormone (GH) suppression test; glucose challenge test for acromegaly

Indications

• assessment of acromegaly

Reference interval

• suppression of serum GH to < 0.2 ng/mL

Clinical significance

• no or incomplete suppression from high baseline level in acromegaly or gigantism
• patients with acromegaly typically have baseline levels > 10 ng/mL
• paradoxical rises in GH are possible in patients with acromegaly.
• patients with liver disease, uremia or heroin addiction may fail to suppress
• partial suppression may be seen in patients with anorexia nervosa

Increases

(increases in serum GH post suppression with glucose)

• acromegaly or gigantism
• liver disease, uremia or heroin addiction
• anorexia nervos

Procedure

• overnight fast:
• 75 or 100 g of glucose PO or 1.75 g/kg
• measure serum glucose & serum growth hormone at 0, 30, 60, 90, 120 & 150 minutes

Interpretation

• serum growth hormone of < 0.2 ng/mL is a normal response
• serum growth hormone > 1.0 ng/mL or > 0.3 ng/mL with ultra- sensitive assay is diagnostic for acromegaly
• other interpretations
  • elevated serum GH 1-2 hours after 100 g of glucose (failure to suppress to < 1 ng/mL)
  • elevated serum GH 30, 60 & 90 minutes after a glucose load (failure to suppress to < 5 ng/mL)
  • elevated serum GH 30, 60,90, 120 & 150 minutes after 75 glucose load (failure to suppress to < 1 ng/mL)

More general terms

• glucose challenge (tolerance) test

Additional terms

• acromegaly
• growth hormone (GH) stimulation test
• growth hormone (somatotropin) in serum