Effects of acute stimulation with luteinizing hormone-releasing hormone (LRH) on biologically active and immunoreactive serum luteinizing hormone (LH) in pubertal boys.

The responses of biologically active LH (BIO-LH) and immunoreactive LH (RIA-LH) to acute stimulation with LRH (0.1 mg iv) were studied in 8 pubertal boys (9-15 years, 2nd-4th Tanner's stage), and in 10 healthy adult men (20-46 years). Serum levels of BIO-LH were assessed by an in vitro bioassay method based upon testosterone production by mechanically dispersed mouse Leydig cell preparations. In pubertal boys the mean BIO-LH/RIA-LH (B/I) ratio of basally secreted LH was significantly lower than in adult men (1.2 +/- 0.2 (SEM) and 2.2 +/- 0.2 respectively, P less than 0.01). After acute administration of LRH the mean B/I ratio of circulating LH showed a significant increase from the basal value in pubertal boys (2.6 +/- 0.2, P less than 0.01 vs basal values), whereas no significant difference in LH B/I ratios were demonstrated throughout the study period in adult men (2.1 +/- 0.1, P = NS vs basal values). In agreement with this finding, the mean relative maximum response for BIO-LH (BIO-LH delta %) was higher in pubertal boys than in adult men (1702.7 +/- 500.3 and 499.6 +/- 65.4% respectively, P less than 0.05), whereas the mean RIA-LH delta % was similar in both groups (609.1 +/- 85.1 and 534.1 +/- 75.5% respectively, P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)