Interaction of L-dopa and GHRH on GH secretion in normal men

摘要: To determine how L-dopa stimulates GH secretion, we investigated its interaction with GHRH in vivo. Six normal men were studied on 4 occasions: 1) L-dopa-TRH: 500 mg orally followed by 200 µg TRH 60 min later; 2) L-dopa-GHRH-TRH: 100 1-44 iv 30 after iv; 3) GHRH-TRH: at 0 min, later 4) test: as a bolus. After L-dopa-TRH GH-levels increased significantly from 0.6 µg/l to 25.8 ± 9.6 (SE) min. Only slight TSH and no PRL increase was observed L-dopa-TRH. L-dopa-GHRH-TRH the GH-increase higher (45.7 11.1 µg/l) compared alone. GHRH-TRH 52.5 12.1 µg/l, which not different obtained when given. serum 6.3 0.7 µU/ml 715 136 µU/ml, respectively, responses The only also (TSH-max: 5.7 0.5 µU/ml; PRL-max: 899 154 µU/ml) Our results show that combination of leads same response only. However, both are than one This observation indicates stimulatory effect secretion is mediated endogenous GHRH. inhibition administration, however, due direct action metabolite dopamine anterior pituitary.