THE EFFECT OF L-DOPA WITH AND WITHOUT DECARBOXYLASE INHIBITOR ON GROWTH HORMONE SECRETION IN CHILDREN WITH SHORT STATURE

Abstract The efficiency of L-dopa alone and L-dopa plus a dopa-decarboxylase inhibitor (carbidopa) in provoking growth hormone (GH) secretion was studied in 40 children with short stature. By preventing the extracerebral metabolism, carbidopa increases the availability of L-dopa to the brain. The study was designed as paired series of growth hormone stimulation tests in which the effect of L-dopa alone, in different dosage schedules, was compared with the same dose level of L-dopa plus carbidopa. When L-dopa was given in full dose (125–500 mg), there was no significant difference in the serum GH concentrations at any time of sampling. In the lower dose level, the stimulant effect of L-dopa alone tended to be exceeded by the combination of L-dopa and carbidopa. The serum GH responses to the different schedules indicate that an optimal hypothalamic dopamine concentration for GH release could be achieved with a considerably lower dose of L-dopa than those employed in previously reported studies. When L-dopa is combined with a dopa decarboxylase inhibitor, the children have the advantage of less side effects in the form of nausea and vomiting.