Basal and LHRH-stimulated gonadotropin levels and the circadian rhythm of testosterone and the effect of exogenous testosterone thereon.
In seven eugonadal men, aged 20-26 years, a fall in plasma and saliva testosterone (T) levels between 8.00 and 16.00 h of the day was observed, but plasma oestradiol-17 beta levels did not show a significant variation. These findings substantiate the existence of a circadian rhythm in T levels. Concurrent with the decrease of T levels over the day, a small but significant rise in basal LH, but not in LHRH-stimulated LH levels were observed. Then the fall of plasma and saliva T levels over the day was prevented by the administration of 80 mg testosterone undecanoate (Andriol, Organon) by mouth at 8.00 h. A rise in plasma T and even more in saliva T levels was measured, which persisted till at least 16.00 h. At this hour basal LH, but not LHRH-stimulated LH levels appeared to be slightly, though significantly depressed. From our data we conclude that fluctuations of T levels of the magnitude of 25% around the baseline values, affect slightly basal LH levels, but not LHRH-stimulated LH levels.
D000328:Adult; D002940:Circadian Rhythm; D004958:Estradiol / Q000097:blood; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007987:Gonadotropin-Releasing Hormone; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D012016:Reference Values; D012463:Saliva / Q000032:analysis; D013739:Testosterone / Q000031:analogs & derivatives / Q000032:analysis* / Q000494:pharmacology; D013997:Time Factors
D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; C010792:testosterone undecanoate