Pituitary response to luteinizing hormone-releasing hormone in women with variant luteinizing hormone
European Journal of Endocrinology
Objective: To assess the LH response of the pituitary gland to GnRH stimulation in healthy women with a mutant b-subunit (Trp8 to Arg8 and Ile15 to Thr15). Design: Clinical study. Patients: We studied 40 healthy non-pregnant Japanese women of known zygosity for the LH b-subunit gene (3 homozygotes for the mutant gene, 17 heterozygotes, and 20 homozygotes for the wild type). All women had normal ovulatory cycles. Measurements: Serum LH status was determined by comparing LH immunoassays results
... unoassays results using a monoclonal antibody recognizing only wild-type LH with those from a polyclonal antibody assay recognizing both variant and wild-type LH. The ratio of monoclonal to polyclonal immunoassay results determined the serum LH status. LH secretion in response to a GnRH stimulation test was measured. Results: All women with the wild-type LH showed a normal response of LH to GnRH according to both assays. Over the time course of the response, the ratios in women with wild-type LH showed no remarkable changes. The response curves in women heterozygous for the mutant peaked 15±30 min after GnRH injection; their response patterns included a statistically signi®cant decrease in the rates of response at 15 min after injection. Conclusions: There are the differences in circulatory kinetics between the two LH forms and in regulation of the two types of LHb genes. The maximal response of the variant LH to pituitary stimulation with GnRH appears to be greater than that of wild-type LH. Figure 2 Mean (6S.D.) concentrations of serum LH in the GnRH stimulation test, as measured by the Immulyze and SPAC-S methods. (A) Women with wild-type LH. (B) Women heterozygous for variant LH b-subunit. Within a group, values with different superscript letters are signi®cantly different (P<0.01, ANOVA), and asterisks (*) denote a pair of mean values that are signi®cantly different (P<0.01, ANOVA). §P<0.0001, ³P<0.001, ¶P<0.01, ²P<0.05 compared with before injection. **P<0.001 compared with LH by SPAC-S.