Keywords

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FormalPara Indication:
  1. 1.

    In order to evaluate patients with suspected GH deficiency

  2. 2.

    In order to assess growth hormone reserve when insulin tolerance test is contraindicated/not preferred

FormalPara Preparation:

NPO except water after midnight and during test

Confirm testing with physician prior to proceeding.

FormalPara Materials needed:

Five gold top tubes

GHRH

Arginine

figure a

Confirm the medication doses with physician.

FormalPara Assay for GH:

GH:Immunoenzymatic Assay

FormalPara Precautions:

Facial flushing occurs immediately after administration of GHRH in about half of the patients. Paresthesias, nausea, and abnormal taste sensation occur in 5–10 % patients [1].

FormalPara Interpretation:

Serum growth hormone (< 4.1 ng/mL) confirms the diagnosis of growth hormone deficiency with 95 % sensitivity and 91 % specificity compared to 96 % sensitivity and 92 % specificity of ITT (GH < 5.1 ng/mL) in patients with BMI > 30 [1].

Suggested GH cut-offs based on BMI [2]

BMI < 25 kg/m2

Peak GH < 11.5 mcg/L

BMI 25–30 kg/m2

Peak GH < 8 mcg/L

BMI > 30 kg/m2

Peak GH < 4.1 mcg/L

FormalPara Caveats:

  • The ARG–GHRH test performs equally well in diagnosing GHD, indicating that it provides an ideal alternative to the ITT [1].

  • This test can give a falsely normal GH response in patients with GHD of hypothalamic origin, e.g., those having received irradiation of the hypothalamic-pituitary region because GHRH directly stimulates the pituitary [3].

  • Decreased responsiveness to stimulation tests such as GHRH, ITT, and ARG–GHRH has been demonstrated in subjects with obesity and/or abdominal adiposity [4].

FormalPara Procedure:

Completed as outpatient.

  1. 1.

    Check the Dynamic Testing Order Sheet.

  2. 2.

    Establish hep-lock.

  3. 3.

    Draw baseline, timed samples after 30 min of patient rest for GH

  4. 4.

    Inject 1 mcg/kg of GHRH IV in a single push followed immediately by 0.5 g/kg (to a maximum of 30 g) of arginine HCl IV infusion over 30 min as ordered by physician and followed by 10 cc saline flush.

  5. 5.

    Note the time of GHRH and arginine injection.

  6. 6.

    Obtain samples for GH at: 30, 0, 60, 90, and 120 min.

Patient label:▁

Documentation for medication orders:▁

Ordering provider’s signature: ▁ Date:▁

GHRH–arginine test

Time

Growth hormone

Basal (after 30 min of rest)

  

Post-30 min

  

Post-60 min

  

Post-90 min

  

Post-120 min