The utility of the gonadotrophin releasing hormone (GnRH) test in the diagnosis of polycystic ovary syndrome (PCOS)

Abstract

INTRODUCTION: Polycystic ovary syndrome (PCOS) is characterised by increased frequency of hypothalamic GnRH pulses leading to
a relative increase in LH synthesis by the pituitary. As GnRH stimulation can reveal a relative LH excess, we have endeavoured to assess
whether GnRH test might be useful in the diagnosis of PCOS.

MATERIAL AND METHODS: The study involved 185 subjects: a PCOS group, n = 151, all with oligo- or amenorrhoea, aged (mean ± SD) 24.8 ±
± 5.4 years, BMI 24.5 ± 6.0 kg/m²; and regularly menstruating controls, n = 34, aged 26.6 ± 5.0 years, BMI 24.6 ± 5.5 kg/m². In 121 subjects
with PCOS and in 32 controls, serum LH and FSH were measured before (0 minutes) and 30 and 60 minutes after GnRH stimulation
(100 μg i.v.). Insulin resistance was assessed by HOMA and Insulin Resistance Index derived from glucose and insulin concentrations
during 75 gram oral glucose tolerance test.

RESULTS: Women with PCOS had higher testosterone (p = 0.0002), androstendione (p = 0.0021), 17OH-progesterone (p < 0.0001) and were
more insulin resistant. Raised concentrations of at least one androgen were, however, found only in 58.1% of women with PCOS. Baseline
and stimulated LH concentrations were higher in PCOS (9.09 ± 5.56 vs 4.83 ± 1.71 IU/L, 35.48 ± 31.4 vs 16.30 ± 6.68 IU/L, 33.86 ± 31.8 vs
13.45 ± 5.2 IU/L, at 0, 30 and 60 mins post GnRH, respectively, p < 0.0001). There was no difference in baseline or stimulated FSH concentrations
between groups. Relative increases of LH or FSH in comparison to respective baseline values were similar in both groups. There
was, however, a marked increase in LH/FSH ratio in PCOS in comparison to controls (LH0 min/FSH0 min 1.59 ± 0.95 vs 0.76 ± 0.2, LH30 min
/FSH30 min 4.07 ± 3.0 vs 1.89 ± 0.79, LH60 min/FSH60 min 3.56 ± 2.58 vs 1.55 ± 0.63, p < 0.0001 at all time points). Further analysis revealed that
LH30 min/FSH30 min > 2.11 or LH60 min/FSH60 min > 1.72 had 78.3% and 87.5% sensitivity and 81.7% and 81.3% specificity for the diagnosis of
PCOS, respectively.

CONCLUSIONS: Women with PCOS have higher baseline and GnRH-stimulated LH concentrations. GnRH stimulation results in an increase
in LH/FSH ratio in women with PCOS. Therefore we postulate that this phenomenon might be potentially useful as an additional tool in
the diagnosis of PCOS. (Pol J Endocrinol 2011; 62 (2): 120–128)