The effects of l-dopa administration on the prolactin levels in short-stature subjects]

In this study, on the basis of the inhibiting action of l-dopa administration on prolactin (PRL) secretion, we evaluated in a number of short children the levels of PRL during the provocative stimuli test with l-dopa in order to identify an index able to give reliability to the test and to investigate whether some differences may exist among the subjects showing a different response in growth hormone (GH) secretion to l-dopa. We examined 76 subjects (44 boys and 32 girls) with chronological age from 4.5-15.17 years. The subjects, on the basis of the GH peaks during two provocative stimuli tests [l-dopa and insulin-induced hypoglycemia (IIH)], were subdivided into 3 groups: group 1 (n = 24) with both deficient responses (peak less than 10 ng/ml); group 2 (n = 28) with discordant responses and further subdivided into group 2a (n = 14) with normal responses to IIH and 2b (n = 14) with a normal response to l-dopa; group 3 (n = 24) with both normal responses. PRL levels peaked between times -20' (58 cases) and +20' (2 cases) whereas nadir occurred between +80' (4 cases) and +120 (48 cases) without any significant difference (p = ns) among the groups. PRL levels significantly decreased in all groups, also in those with a deficient response to l-dopa (1 and 2a); furthermore no significant correlation between PRL and GH levels was demonstrated. In conclusion, this study showed the importance of PRL evaluation during l-dopa test in order to give reliability to the test and did not demonstrate any difference in PRL levels among the examined groups of short children.