THE INTERNATIONAL REFERENCE PREPARATION OF HUMAN PITUITARY LUTEINIZING HORMONE, FOR IMMUNOASSAY

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Abstract
The preparation and nature of the International Reference Preparation of Human Pituitary Luteinizing Hormone for Immunoassay are described. A collaborative assay of this material (coded 68/40) in terms of the International Reference Preparation of Human Pituitary Gonadotropins (FSH [follicle stimulating hormone] and LH [luteinizing hormone] (ICSH)), for Bioassay (coded 69/104) was carried out by 12 laboratories in 7 different countries, using different bioassay and immunoassay methods. The weighted combined potency estimate (with 95% confidence limits) was 52.1 (46.3-58.7) IU/ampoule with male accessory reproductive organ weight gain assays; 80.2 (73.2-87.9) IU/ampoule with ovarian ascorbate depletion assays; 127 (124-129) IU/ampoule with in vitro Leydig cell testosterone production assays; and 124 (121-126) IU/ampoule with testis receptor binding assays. Immunoassay estimates in terms of the same standard were heterogeneous and gave an unweighted mean potency estimate of 33.2 IU with 95% confidence limits of 14.8-74.4 IU/ampoule. Estimates from different methods gave significantly different results, and the reasons for this are discussed in terms of the differences between the materials being compared and the methods used in the comparison. These data illustrate the conceptual difficulties involved in comparing heterogeneous reference preparations, especially by both bioassay and immunoassay, and some of the causes of inevitable discontinuity of assay results.