DETERMINATION OF A COMMON GENETIC VARIANT OF LUTEINIZING-HORMONE USING DNA HYBRIDIZATION AND IMMUNOASSAYS

OBJECTIVE An immunologically anomalous form of LH, due to two point mu tations in codons 8 and 15 of the LH beta gene, has previously been de scribed. LH status, i.e. the discrimination between wild-type (WT) and variant (V) LH, is usually determined by immunoassays, which can be u nreliable at low serum concentrations of LH. A DNA hybridization assay was therefore developed to score the LH genotype in all subjects, ind ependent of their serum LH concentrations. To evaluate the performance of the hybridization method, and to expand our observations of the wo rldwide occurrence of the V-LH, we determined its frequency in additio nal populations. To confirm the connection between the anomalous immun oreactivity and the V-LH beta gene, we also sequenced the LH beta subu nit gene of a homozygous person. DESIGN According to the ratio of two immunoassays, one detecting only WT-LH and the other detecting equally WT and V-LH, individuals can be classified as homozygotes for the V-L H beta allele, heterozygotes or WT. DNA samples from persons with know n LH status, according to the immunoassays, were used for the developm ent and evaluation of a new allele-specific DNA hybridization assay. T his assay, and PCR and restriction fragment length polymorphism analys is, were used to determine the frequency of the V-LH beta allele in DN A samples obtained from eight populations. PATIENTS Ambulatory adult m en and women, apparently healthy and with no endocrine disorders. RESU LTS The LH genotyping by immunoassays and by the new hybridization met hod gave identical results with all samples analysed (n = 25). The V-L H beta subunit was observed to always have the two point mutations, an d to be identical with the ones previously reported. The V-LH beta car rier frequency in the DNA samples collected from various populations v aried between 0 and 53.5%. CONCLUSIONS The immunoassay technique and t he hybridization assay can be used as alternatives to determine the LH status. A great variation in carrier frequency of the V-LH beta allel e is observed in different populations.