The impact of the L-dopa test on cortisol response and its comparison with the insulin tolerance test (comparative clinical study).

Insulin tolerance tests (ITTs), glucagon tests, and low or standard-dose adrenocorticotropic hormone tests are used to evaluate the hypothalamic-pituitary-adrenal (HPA) axis. While ITT is considered the gold standard test for stimulating both the cortisol and growth hormone axis, its use in young children carries a risk of hypoglycemia, making it potentially unsafe. Recent studies indicate that L-dopa stimulates the release of adrenocorticotropic hormone and cortisol. This study aimed to evaluate the L-dopa test-evoked cortisol response in short children and compare it with the ITT. L-dopa and ITTs were used as growth hormone stimulation tests. Blood samples were collected from the subjects at 0, 30th, 60th, 90th, and 120th minutes to analyze growth hormone and cortisol levels. A serum cortisol level of >18 µg/dL in both tests was considered an adequate response for the HPA axis. All cases (100%) in the ITT showed a peak cortisol response more significant than 18 µg/dL. In comparison, an adequate cortisol response was achieved in 18 cases (90%) in the L-dopa test. When the time to reach peak cortisol levels was evaluated, in the L-dopa test, it was at the 120th minute in 70% of the cases (14 cases), and in the ITT, it was at the 60th minute in 65% of the cases (13 cases). The L-dopa stimulation test effectively controlled the HPA axis and stimulated cortisol levels similarly to ITT. In situations where the use of ITT is risky, the L-dopa test can be employed to monitor the HPA axis.