The Levodopa Test of Growth Hormone Reserve in Children

The efficiency of levodopa administration as a test of growth hormone (GH) reserve in children was studied. Growth hormone levels increased during the levodopa test in 20 of 21 control children to levels comparable to those observed during insulin provocation. All ten hyposomatotropic subjects released lesser amounts of GH in response to levodopa treatment. Side effects were limited to occasional nausea or emesis or both. Thus, the levodopa test proved as reliable as the insulin tolerance test (ITT), while the dangers of the ITT were avoided. Studies of plasma cortisol, thyrotropin, prolactin, and gonadotropin levels supported the view that levodopa provokes GH discharge via stimulation of hypothalamic GH-releasing factor. The levodopa test does not require the attendance of a physician and is a good means of screening for GH-deficiency.