L-Dopa Stimulates Cortisol Secretion through Adrenocorticotropic Hormone Release in Short Children.

BACKGROUND/AIMS: We recently showed that L-Dopa administration is a potent stimulator of cortisol secretion in children with short stature. Herein, we examined whether adrenocorticotropic hormone (ACTH) is implicated in the mechanism by which cortisol is stimulated during the L-Dopa test.

METHODS

Nineteen children with short stature who fulfilled the auxological criteria for growth hormone (GH) deficiency and had a subnormal GH response to glucagon stimulation underwent a second GH stimulation test (L-Dopa test). Serum GH, cortisol and plasma ACTH were determined at baseline and every 30 min up to 120 min after oral L-Dopa administration. Peak values of GH >10 ng/ml, cortisol >18 μg/dl and ACTH >52 pg/ml were considered as normal response.

RESULTS

Normal response rates were 10.5% (2/19) for GH, 94.7% (18/19) for cortisol and 68.4% (13/19) for ACTH. Among the children with a normal response in ACTH, its concentration increased from a basal value (mean ± standard deviation) of 23.3 ± 9.6 to 290.3 ± 221 pg/ml, almost always 90-120 min after L-Dopa administration. Mean peak cortisol was 36.2 ± 9.1 μg/dl, and it peaked almost simultaneously with ACTH.

CONCLUSION

Our data suggest a stimulatory effect of the dopaminergic system on the hypothalamic-pituitary-adrenal axis.