title: The pulsatile secretion of bioactive luteinising hormone in normal adult men.
abstract: We have studied bioactive and immunoreactive LH pulsatility in 11 normal men. The temporal relationship of plasma LH, testosterone, and FSH were also investigated. Blood samples were taken at 10-minute intervals for 6 h and bioactive LH levels were determined using an in vitro mouse Leydig cell bioassay. Testosterone, LH and FSH were determined by standard radioimmunoassay. Twenty-two bioactive LH pulses were detected (amplitude 8.5 +/- 4.9 IU/l, mean +/- SD) with a frequency of 2 +/- 0.8/6 h compared with only 18 immunoreactive LH pulses (amplitude of 3.6 +/- 1.8 IU/l) and a frequency of 1.6 +/- 0.5/6 h. Bioactive:immunoreactive LH ratios increased (p less than 0.01) from the preceding pulse nadirs (2.26, range 1.66-4.28) to the pulse peaks (2.71, range 1.99-4.67). Twenty FSH pulses (seen in all but one subject) of low amplitude (0.7 +/- 0.6, median 0.5 IU/l) were also present. There was a close temporal relationship between testosterone and FSH secretion with bioactive and immunoreactive LH pulses with lags of 30-60 and 0 min, respectively. We conclude that immunoreactive LH pulses are discordant from bioactive LH pulses in 18% of occasions. Further, the mean amplitude of bioactive episodes were approximately 2.6 times greater than that of immunoreactive episodes, whereas interpulse period and pulse duration were similar. The increase in bioactive:immunoreactive ratio at pulse peaks may indicate that in normal men LH pulses are enriched with a more biopotent form of the molecule.
authors.affiliation: Department of Medicine (Clinical Biochemistry), University of Manchester, Hope Hospital, Salford, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Talbot
authors.forename: R S
authors.initials: RS
authors.lastname: Rodger
authors.forename: S M
authors.initials: SM
authors.lastname: Shalet
authors.forename: M D
authors.initials: MD
authors.lastname: Littley
authors.forename: W R
authors.initials: WR
authors.lastname: Robertson
mesh_terms: D000328:Adult; D000818:Animals; D001681:Biological Assay; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007985:Leydig Cells / Q000378:metabolism; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D008297:Male; D051379:Mice; D010507:Periodicity; D011863:Radioimmunoassay; D013739:Testosterone / Q000097:blood; D013997:Time Factors
chemical_list: D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone