What is the role of provocative testing in the workup of hyposomatotropism (growth hormone deficiency [GHD])?

Updated: Jan 24, 2019
  • Author: Sunil Kumar Sinha, MD; Chief Editor: Robert P Hoffman, MD  more...
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Answer

Provocative GH testing is criticized for several reasons, including the following [60] :

  • None of the tests reproduces the physiologic secretory pattern of GH because they involve the use of pharmacologic stimuli to indirectly assess physiologic GH production.

  • Individual clinicians assign what are essentially arbitrary definitions for subnormal responses (ie, cutoffs for peak serum GH values) to provocation.

  • The reproducibility of provocative tests and GH RIAs is limited. Many pediatric endocrinologists apply other clinical criteria (eg, growth velocity Z score below -2) and do not perform provocative GH tests to diagnose GHD.

Despite limitations, provocative GH tests remain helpful ways to measure GH reserve. Pediatric endocrinologists use physiologic stimuli (eg, strenuous exercise, fasting, deep sleep) and pharmacologic stimuli (eg, clonidine, levodopa-propranolol, glucagon, arginine, insulin) to provoke GH secretion. In euthyroid children, all of the tests must be performed after overnight fasting.

To improve diagnostic sensitivity and specificity, at least 2 provocative tests are performed. Immediately before and during the earliest phases of puberty, GH production is often indistinguishable in unaffected children and in children with GHD. Serum GH concentrations typically rise during puberty. Many investigators suggest that children approaching puberty should be given gonadal steroids to prime the growth hormone-releasing hormone (GHRH)-GH axis before testing.

Most clinicians use a peak serum GH concentration of more than 10 ng/mL (30 IU) to exclude GHD in children. Specific provocative tests are described below.


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