title: Sensitive immunoassay and in vitro bioassay demonstrate constant bioactive/immunoreactive ratio of luteinizing hormone in healthy boys during the pubertal maturation.
abstract: The quality of serum LH was assessed during pubertal maturation in boys by measuring immunoreactive (I) LH by a time-resolved immunofluorometric assay (IFMA, Delfia), and bioactive (B) LH by a sensitized in vitro bioassay. Seven samples were collected at 3-mo intervals from 14 healthy boys (median starting age 11.8 y) during pubertal maturation from Tanner stage I-III or II-IV (n = 7 for each). The mouse Leydig cell in vitro bioassay was sensitized 10-fold, to 0.05-0.1 IU/L, by including 1.5 mumol/L of forskolin in the incubation medium. The I- and B-LH levels showed good linear correlation throughout the concentration range analyzed. Mean I-LH increased between the pubertal stages I-IV from 0.42 to 2.24 IU/L and that of B-LH from 1.35 to 5.04 IU/L. No concomitant change occurred in the B-LH/I-LH (B/I) ratio, which was 2.84 +/- 0.54 in stage I and 2.58 +/- 0.48 in stage IV (mean +/- SEM, n = 7). Although the B/I ratios of LH varied from 0.59 to 5.85 in the samples analyzed, the intraindividual variation was small (mean coefficient of variance, 22%). In conclusion, IFMA and sensitized in vitro bioassay showed in healthy boys a similar 4-5-fold increase in the mean LH concentration during pubertal maturation, with no concomitant change in the B/I ratio. The sensitized in vitro bioassay of LH is useful for analysis of the low peripubertal LH levels. The good correlation between the I-LH and B-LH levels, and the lack of change in LH B/I ratio, indicate that IFMA correctly estimates the LH levels upon evaluation of pubertal maturation.
authors.affiliation: Department of Physiology, University of Turku, Finland.
authors.forename: I T
authors.initials: IT
authors.lastname: Huhtaniemi
authors.forename: A M
authors.initials: AM
authors.lastname: Haavisto
authors.forename: R
authors.initials: R
authors.lastname: Anttila
authors.forename: M A
authors.initials: MA
authors.lastname: Siimes
authors.forename: L
authors.initials: L
authors.lastname: Dunkel
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods*; D002478:Cells, Cultured; D002648:Child; D005576:Colforsin / Q000494:pharmacology; D015200:Fluoroimmunoassay / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D007985:Leydig Cells / Q000166:cytology; D016014:Linear Models; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D051379:Mice; D011627:Puberty; D012680:Sensitivity and Specificity
chemical_list: D005576:Colforsin; D007986:Luteinizing Hormone