Growth hormone stimulation

Specimen:

The patient should be fasting.

2 mL blood in a lithium heparin or plain tube taken at intervals, as indicated.

Method:

Glucose - spectrophotometry.

Growth hormone - immunoassay.

Protocol:

Exercise, arginine-insulin: recommend specialist assessment.

L-dopa and clonidine are used in provocative tests.

Reference Interval:

Peak growth hormone > 20 mU/L (10 µg/L).

Application:

Diagnosis of growth hormone deficiency.

The arginine-insulin test may be done as an initial test or following a negative exercise test.

Interpretation:

Plasma glucose must decrease to < 2.2 mmol/L for the arginine-insulin test to be valid.

A growth hormone level of > 20 mU/L, with either test, excludes growth hormone deficiency.

Reference:

Hintz RL. J Pediatr Endocrinol Metab. 2003; 3: 631-5.