Objective of the test
Investigation of somatotropic function in cases of growth retardation by testing stimulation of serous growth hormone secretion.
L-Dopa, or levodopa, acts through stimulation of somatocrinin or GHRH, which in turn stimulates synthesis of hGH. It is a little-used first-line test.
Note: The L-DOPA test can also be used to investigate prolactin secretion in adults.
Preparation of the patient
Subject fasting for 12 hours and at rest for 30 minutes.
Organise medical monitoring for the duration of the test due to adverse effects in the form of hypotension, nausea, and psychiatric disorders.
Do not perform the test on patients with suspected cardiovascular decompensation or who are susceptible to decompensation.
Product
LEVODOPA® or LARODOPA®
Dose
For stimulation of hGH, the following doses are used:
- 125 mg per os for children < 30 kg
- 250 mg per os for children > 30 kg
- 500 mg per os above 50 kg
Protocol
Allow for 6 dry tubes for measurement of hGH and 1 EDTA tube for possible measurement of IGF-1.
- T-30 minutes: Collect one tube for hGH
- T0: Collect one tube for hGH and one tube for IGF-1
- Administer the L-DOPA by oral route
- T30, T60, T90, T120 minutes: Collect one tube for hGH at each time interval
Samples
Following centrifugation of the samples, the serum is frozen at -20°C.
Measurement
- hGH
- IGF-1
