Laboratoire de biochimie-hormonologie, centre de biologie pathologie, CHRU de Lille, Lille
- Key words: LH, FSH, isoforms, N-glycans, bioactivity
- DOI : 10.1684/mte.2017.0665
- Page(s) : 181-8
- Published in: 2017
The gonadotropins LH and FSH are pituitary glycoprotein hormones that exhibit both structural macro- and micro-heterogeneity. The latter is due to a variability in the nature and number of terminal motifs (sialic acids, sulphate groups) of their N-glycans. Thus the pituitary synthesizes and releases in the bloodstream a dozen of isoforms or isoglycoforms of LH and FSH, each having a specific pI. This isoform profile varies according to key stages of reproductive life (puberty, menopause), during the menstrual cycle and is dependent on the level of blood estradiol. Overall, the less acid isoforms are the most active in vitro in cellular systems whereas in vivo the isoforms richest in sialic acid terminal motifs have the longest half-life. This explains why, according to the mode of production (extraction of urine, recombinant hormone produced in animal or human cells), the isoform profile of gonadotropins used in therapy will be different which will affect their biological activity. Similarly, the structural heterogeneity of LH and FSH explains the great inter-methods variability in the results found in clinical biology.