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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 [1] 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 [1] - other interpretations - elevated serum GH 1-2 hours after 100 g of glucose (failure to suppress to < 1 ng/mL) [3] - elevated serum GH 30, 60 & 90 minutes after a glucose load (failure to suppress to < 5 ng/mL) [2] - elevated serum GH 30, 60,90, 120 & 150 minutes after 75 glucose load (failure to suppress to < 1 ng/mL) [2]

Related

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

General

glucose challenge (tolerance) test

References

  1. Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
  2. Medical Knowledge Self Assessment Program (MKSAP) 17, American College of Physicians, Philadelphia 2015
  3. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 195-96