Variation in the biologic and biochemical characteristics of human menopausal gonadotropin

Lot differences in the biopotency of human menopausal gonadotropin (hMG) were evaluated and the potential biochemical basis was investigated. The in vivo biopotency of hMG was assessed by a unique bioassay that evaluates the number of ova shed in the cyclic hamster in response to hMG administration. Significant variation in hMG lots was observed using this assay. When subjected to chromatofocusing, hMG displayed five immunoreactive follicle-stimulating hormone (FSH) isohormones and nine luteinizing hormone (LH) isohormones. The relative distribution of FSH, but not LH isohormones, was slightly but significantly different between the lots tested. These data indicate that significant differences exist in the ability of commercially available hMG to stimulate follicular development and ovulation. The biochemical basis for these differences in in vivo biopotency remains to be elucidated.