Gonadotrophin heterogeneity and biopotency: implications for assisted reproduction

The extensive heterogeneity of the gonadotrophin hormones, folliclestimulating hormone (FSH) and luteinizing hormone (LH), is due primarily tothe heterogeneous nature of their carbohydrate side- chains, in particularsialic acid residues. In this review, we discuss the role of carbohydratechains in receptor binding and activation, biological activity, andmetabolic half-life. The synthesis and secretion of the various glycoformsof both FSH and LH appear to be under endocrine control withgonadotrophin-releasing hormone (GnRH), oestradiol and testosterone playingimportant roles. Evidence for different glycoforms having variablebiopotency or different encoded functions is increasing, and the productionand secretion of more or less acidic gonadotrophin species in differentphysiological states may represent an important mechanism whereby thepituitary regulates gonadal cell and organ function. This has potentialimportance for the development of new pharmaceutical reagents and newtherapeutic regimens in assisted reproduction. It is envisaged that the useof existing and new forms of FSH/LH will allow patients to be treated in amore controlled and physiological manner, with treatment regimensindividualized to the needs of the patient.