What is the Clinical Relevance of Follicle-Stimulating Hormone Isoforms in Fertility Treatment?

Follicle-stimulating hormone, both naturally synthesized and as commercial preparations, exists as different isoforms. Variation in the process of glycosylation, particularly in the number of terminal sialic-acid residues, gives rise to isoforms of varying acidic profiles with differences in half-life and bioactivity. Based on the known follicle-stimulating hormone isoform variation across the reproductive cycle, it is possible that the follicle-stimulating hormone isoform profile used in controlled ovarian stimulation may impact follicular recruitment and clinical treatment outcomes. In light of the uncertainty regarding the clinical relevance of follicle-stimulating hormone isoforms in fertility treatment, published studies exploring this topic are reviewed.