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Effect of repetitive (triple) LRH/TRH administration at different times of the day on testosterone serum levels

Abstract:

To elucidate the effect on testosterone serum levels of simultaneous increases of luteinizing hormone (LH) and prolactin (PRL), 8 healthy men were challenged i.v. with a triple stimulation with 50 μg of LH-releasing hormone (LRH) and 100 μg of thyrotropin-releasing hormone (TRH) in a single bolus at 0, 90 and 180 min, receiving the first pulse of hypothalamic hormones either at 02.00 h (02.00 h test) or at 09.00 h (09.00 h test). In addition, a placebo was injected instead of LRH-TRH to evaluate the spontaneous hormonal changes during both periods of study. When LRH/TRH were injected at 90-min intervals a significant increase in testosterone occurred during the 02.00 h test, while the LH and PRL peaks induced by LRH/TRH during the 09.00 h test were not followed by a distinct testosterone release.