Lack of an effect of melatonin on the basal and L-dopa stimulated growth hormone secretion in men.
The oral administration of melatonin to men has been reported to cause a rapid and significant elevation of serum GH, and to inhibit GH release after stimulation by L-Dopa. We studied the effect of melatonin i.v. on the basal and L-Dopa stimulated GH secretion in four young men. Each subject's control response to L-Dopa was first studied by an oral administration to 500 mg of L-Dopa under a placebo infusion and was followed 2 weeks later by a similar study under melatonin infusion, 2.1 mg/min (total dose of 500 mg). The infusion of melatonin was given for a 4-hour period, 2 hours before and 2 hours after the L-Dopa stimulation. Blood samples for GH were obtained at 30-min intervals. Basal values of serum GH did not rise under the melatonin infusion and peak GH values following L-Dopa stimulation during the control infusion and the melatonin infusion also did not differ (2 +/- 0.5 to 22 +/- 6 and 2 +/- 0.8 to 25 +/- 4 ng/ml respectively). Our data suggest that under an acute constant infusion melatonin does not stimulate GH secretion, nor does it interfere with the L-Dopa stimulated GH response in men.
D000328:Adult; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D007980:Levodopa; D008297:Male; D008550:Melatonin
D007980:Levodopa; D013006:Growth Hormone; D008550:Melatonin