Hereditary abnormality of luteinizing hormone resulting in discrepant serum concentrations determined by different assays.

We herein report familial defects in the molecular structure of luteinizing hormone (LH). The propositus was a 29-year-old women with repeated abortion in whom the serum LH concentration was extremely low determined by an immunoradiometric assay utilizing two monoclonal antibodies for the intact LH dimer and beta-subunit of LH (SPAC-S kit). Further studies on the serum LH concentration in this propositus by five different assay systems gave various results ranging from low to normal values. Bioassay of the propositus's LH using C57 black mice showed normal in biological activity. These data suggest that LH in the propositus is abnormal in terms of its molecular structure located in the bond region between alpha and beta subunits. A family study showed that the bioactivity of LH was normal in all family members. The serum LH was not detected in either the propositus or her brother with the SPAC-S kit even after the administration of LHRH, while the serum LH concentrations in the father, mother and sister were approximately half the normal range, indicating that the defect is hereditary and the mode of inheritance is autosomal dominant: the propositus and brother were homozygously affected, and the parents and sister heterozygously affected.