GHRH–Arginine GH Stimulation Test

Confirm the medication doses with physician.

Assay for GH:

GH:Immunoenzymatic Assay

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].

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

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].