Pulsatile Release of Bioactive Luteinizing Hormone in Prepubertal Girls: Discordance with Immunoreactive Luteinizing Hormone Pulses

Abstract

An assessment of pulsatile secretion of luteinizing hormone (LH), measured by both immunoassay (I-LH) and rat interstitial cell testosterone production bioassay (B-LH), as well as of follicle-stimulating hormone and glycoprotein hormone alpha-subunit was carried out in seven normal prepubertal and six normal premenarcheal pubertal girls. Samples were obtained at 20-min intervals for a 6-h period. The hormone secretion profiles were analyzed by several computerized methods yielding pulse frequency and amplitude, interpulse basal levels, and percentage increments, with bio/immuno ratios calculated for peak and basal concentrations. In these prepubertal girls, mean B-LH levels were 12% of I-LH, with B/I ratio of 0.13; 30% of samples were below assay sensitivity (0.10 mIU/ml) for B-LH, but all I-LH (1.25 mIU/ml) were detectable. In the pubertal group, B-LH levels were 30% of I-LH, with mean B/I ratio of 0.24 and undetectable B-LH in 29% of samples. Pulsatile secretion in prepubertal girls was found in five of seven (1/150 min) for B-LH and six of seven (1/212 min) for I-LH; only two of six pubertal girls had detectable pulses. Discordance of B- and I-LH pulses were frequent, with 56% of B-LH pulses lacking an I-LH pulse and 47% of I-LH pulses not having a B-LH pulse. These data demonstrate that both B- and I-LH are secreted episodically in prepubertal girls; I-LH-like material is present in higher concentrations than B-LH in these girls; and substantial discordance of B- and I-LH pulses exist.(ABSTRACT TRUNCATED AT 250 WORDS)