A common variant of the LHb subunit has a varying prevalence in various ethnic groups. The consequences of the presence of mutated luteinizing hormone (LH) concern borderline alterations in pituitary/gonadal function that could be mediated by an altered action of variant LH on gonadal steroidogenesis. A comparison of plasma concentrations of gonadal steroid sex hormones was completed in women heterozygous for variant LH and in women with the wild type of LH in three different age ranges. The sample was a randomly selected group of 177 normal women 16 to 72 years old. Variant LH was determined by immunofluorimetric methods using two combinations of monoclonal antibodies. The ratios of LH measured by the two assays indicated whether the subject was wild type homozygote, heterozygote or homozygote for the variant LHb allele. The carriers of the variant LH allele in the group of postmenopausal women showed higher serum testosterone levels than those with the wild type LH. This is in agreement with the clinical observations made previously showing a slightly higher androgenic action in the population with variant LH. No differences were detected in serum LH, FSH, epitestosterone and sex hormone binding globulin (SHBG).