The Role of GnRH Receptor Autoantibodies in Polycystic Ovary Syndrome

Abstract

Objective: Is polycystic ovary syndrome (PCOS) associated with activating autoantibodies (AAb) to the second extracellular loop (ECL2) of gonadotropin-releasing hormone receptor (GnRHR)?

Design and methods: We retrospectively screened sera from 40 patients with PCOS and 14 normal controls (NCs) with regular menses using enzyme-linked immunosorbent assay (ELISA) for the presence of GnRHR-ECL2-AAb. We obtained similar data from 40 non-PCOS ovulatory but infertile patients as a control group (OIC) of interest. We analyzed GnRHR-ECL2-AAb activity in purified immunoglobulin (Ig)G using a cell-based GnRHR bioassay.

Results: The mean ELISA value in the PCOS group was markedly higher than the NC (P = .000036) and the OIC (P = .0028) groups. IgG from a sample of 5 PCOS subjects, in contrast to a sample of 5 OIC subjects, demonstrated a dose-dependent increase in GnRHR-stimulating activity qualitatively similar to the acute action of the natural ligand GnRH and the synthetic agonist leuprolide. The GnRHR antagonist cetrorelix significantly suppressed (P < .01) the elevated GnRHR activity induced by IgG from 7 PCOS patients while the IgG activity level from 7 OIC subjects was unchanged. Five other OIC subjects had relatively high ELISA values at or above the 95% confidence limits. On further study, 3 had normal or low activity while 2 had elevated IgG-induced GnRHR activity. One suppressed with cetrorelix while the other did not. The copresence of PCOS IgG increased the responsiveness to GnRH and shifted the dosage response curve to the left (P < .01).

Conclusions: GnRHR-ECL2-AAb are significantly elevated in patients with PCOS compared with NCs. Their presence raises important etiological, diagnostic, and therapeutic implications.

Keywords: GnRH receptor; autoantibodies; polycystic ovary syndrome.

Figure 1.

ELISA detection of GnRHR autoantibodies in patients with PCOS, ovulatory infertile controls (OICs), and normal controls (NC). The box plots indicate the median optical density (OD) value (middle black line) and the 75th and 25th percentiles (upper and lower edges, respectively). Mean OD value is indicated by the blue diamonds and the estimated 95th (solid) and 99th (dashed) percentiles are indicated by the blue lines. PCOS vs NC: P = .000036, unpaired t-test; PCOS vs OIC: P = .0028, paired t-test; OIC vs. NC: P = .077, unpaired t-test. MFI, male factor infertility.

Figure 2.

Dose–response curves of GnRH and leuprolide in the calcium flux assay. Both agonists were tested at concentrations from 10^–10 to 10^–6 M. The data are the mean ± standard error of the mean for 3 assays run in triplicate. The 10^–10 M concentrations were not significantly different from the buffer baseline value, which was arbitrarily assigned a value of 100% for both agonists. The 2 response curves were performed in the same assay. There was a significant dosage response for each agonist.

Figure 3.

The dosage effects of serum IgG from PCOS and OIC subjects on GnRHR activation in the calcium flux assay. There was a significant dosage-dependent increase in PCOS IgG-induced GnRHR activation with a maximal effect at 100 to 150 μg/mL. The OIC IgG activity was not significantly different from the buffer baseline activity and no dosage effect was noted. P < .05, **P < .01 vs OIC, n = 5.

Figure 4.

The effect of GnRHR blockade on serum IgG-induced GnRHR activation in the calcium flux assay. The selective GnRHR blocker cetrorelix (10^–7 M) effectively suppressed the mean elevated GnRHR activity from the PCOS IgG (100 μg/mL, n = 7) to levels not significantly different for the baseline buffer alone. Cetrorelix produced no significant change in the already low mean GnRHR activity in the OIC IgG (100 μg/mL, n = 7). **P < 0.01.

Figure 5.

The effect of cetrorelix on GnRHR activation induced by serum IgG from the five OIC subjects with the highest ELISA OD values. Two of these OIC subjects had an elevated GnRHR activity. One suppressed with cetrorelix (10^–7 M) to levels not significantly different from the buffer baseline while the other did not change. The other 3 of these 5 OIC subjects had relatively low baseline GnRHR activity near that for the baseline buffer values. Two were unchanged by cetrorelix blockade while the third had a small decrease clearly into a level not different from the buffer alone. The absence of a significant decrease in 4 of these 5 subjects following cetrorelix is quite similar to that observed in the control subjects in Fig. 4.

Figure 6.

The effects of PCOS and OIC IgG on GnRH-induced GnRHR activation in the calcium flux assay. The addition of a constant concentration of PCOS IgG (100 μg/mL, n = 7) significantly increased the GnRHR-induced activity dosage response of GnRH alone (10^–9 to 10^–6 M). Addition of a constant concentration of OIC IgG (100 μg/mL, n = 7) had no significant effect on the GnRH dosage response curve. There was no significant rise in the 10^–9 M values compared with the 10^–8 M values in this particular group of transfected cells, although there was a small difference in activity the presence of the PCOS IgG. This leftward shift of the GnRH curve in the presence of a constant concentration of PCOS IgG compared with the GnRH and GnRH + OIC IgG is significantly more than additive. **P < 0.01 vs GnRH or GnRH + OIC IgG alone.