Serum gonadotropin isoforms become more basic after an exogenous challenge of gonadotropin-releasing hormone in children undergoing pubertal development.

Recent clinical studies have questioned whether there is a qualitative change in the circulating isoforms of LH and FSH after stimulation by GnRH. The present study investigated the median charge of serum gonadotropin isoforms before and after an exogenous challenge of 100 micrograms GnRH in 10 girls and 10 boys undergoing pubertal development. All of the children had basal serum levels of LH and FSH and responses 30 and 60 min after GnRH treatment that were considered normal for puberty. LH and FSH in serum and eluates after electrophoresis in 0.10% agarose suspension were measured with sandwich fluoroimmunoassays. The increases in serum gonadotropin concentrations were generally similar for both sexes, but girls had significantly (P < 0.05) higher LH levels at 30 and 60 min than boys and a larger (P < 0.05) relative increase in serum FSH levels after GnRH treatment. In terms of the median charge of serum isoforms, the girls had significantly less negative (i.e. more basic) isoforms of LH (P < 0.05) and ...