Bioactive LH in women with polycystic ovaries and the effect of gonadotrophin suppression

Mechanisms of hypothalamic-pituitary-gonadal disruption in polycystic ovarian syndrome

Although the pathogenesis of polycystic ovarian syndrome (PCOS) is still controversial, a series of investigations has demonstrated an array of neuroendocrine abnormalities as a major component of the syndrome. From a neuroendocrine perspective, patients with PCOS exhibit an accelerated frequency and/or higher amplitude of LH pulses, augmentation of LH secretory burst mass, and a more disorderly LH release. Elevated in vitro LH bioactivity and a preponderance of basic LH isoforms, which correlate positively with elevated serum 17-hydroxyprogesterone, androstenedione, and testosterone concentrations, also characterize adolescents with PCOS. Heightened GnRH drive of gonadotropin secretion and a steroid-permissive milieu appear to jointly promote elevated secretion of basic LH isoforms. Positive feedback is implied, because hypersecretion of highly bioactive LH in PCOS probably contributes to inordinate androgen output. However, the precise nature of feedback disruption remains uncertain. Indeed, recent data suggest that PCOS is marked by anomalies of both feedforward and feedback signaling between GnRH/LH and ovarian androgens. From a single hormone perspective, the individual patterns of LH and androstenedione release are consistently more irregular in patients with PCOS. Bihormonal analysis has disclosed concomitant uncoupling of the pairwise synchrony of LH and testosterone, LH and androstenedione, and testosterone and androstenedione secretion. The foregoing ensemble of findings points to deterioration of both orderly uniglandular and coordinate bihormonal output in PCOS. Additional studies are needed to establish the primary pathophysiologic mechanisms underlying this disorder.

Role of the mutations Trp8 => Arg and Ile15 => Thr of the human luteinizing hormone beta-subunit in women with polycystic ovary syndrome

OBJECTIVE

To evaluate the clinical significance of LH in the form of a mutant beta-subunit in women with polycystic ovary syndrome (PCOS).

DESIGN

Prospective, controlled study.

SETTING

University hospital.

PATIENT(S)

Thirty healthy women and 30 women with PCOS.

INTERVENTION(S)

Clinical, ultrasonographic, and hormonal findings were used to define PCOS. Nucleotide mutations within codons 8 and 15 in the LH beta-subunit gene (Trp8 => Arg and Ile15 => Thr) were analyzed with the use of polymerase chain reaction and subsequent restriction fragment length polymorphism.

MAIN OUTCOME MEASURE(S)

Serum levels of gonadotropins, androgens, E2, and prolactin were determined, and the results of restriction fragment length polymorphism were analyzed.

RESULT(S)

Five women in the control group and one woman in the PCOS group were found to be affected by the LHbeta gene mutations. No difference was observed in serum androgen and E2 levels between the affected women and 25 healthy women who were homozygous for the wild-type LH. However, women whose serum LH levels were < or = 5.1 mIU/mL had a higher risk of having mutant LH.

CONCLUSION(S)

The frequency of LH mutations in women with PCOS is similar to that in healthy women. The presence of the variant does not cause any significant change in serum levels of androgens and E2.

Prevalence of an immunological LH beta-subunit variant in a UK population of healthy women and women with polycystic ovary syndrome

OBJECTIVE

An immunological LH beta-subunit variant has been described, which is undetectable using monoclonal antibodies directed to the intact LH molecule alone. Subjects have been found homozygous or heterozygous for nucleotide mutations within codons 8 and 15 in the LH beta-subunit gene. The prevalence of the variant LH beta-subunit has been estimated in a healthy UK population of women of reproductive age and in women with polycystic ovary syndrome (PCOS). The relationship of the variant molecule to the clinical and hormonal parameters of the subjects has been evaluated.

DESIGN

The control and PCOS subjects were screened for the presence of the mutation by using a ratio of two immunofluorometric assays using monoclonal antibodies (Mab). One assay, not detecting the LH variant, uses a Mab directed to the intact LH molecule and a beta-specific Mab. The other assay, detecting both the variant and wild-type LH, uses two beta-subunit specific Mabs. The mutations in the LH beta-subunit gene were confirmed by restriction fragment length polymorphism. The relationship of the presence of the variant to the clinical and hormonal parameters was assessed by ANOVA.

PATIENTS

Two hundred and twelve normal ovulatory women, of whom 66 (31%) were obese (body mass index > 25) and 146 (69%) non-obese, and 153 women with PCOS, 115 (75%) obese and 38 (25%) non-obese participated in the study.

RESULTS

The variant LH was detected in 31 (15%) controls and 32 (21%) PCOS subjects (P = 0.124) using specific Mab. Obese PCOS had a higher incidence of the heterozygous LH variant compared to obese controls (odds ratio 2.5, P = 0.03), and compared to non-obese PCOS (odds ratio 6.3, P = 0.01). The previously described two mutations in codon 8 and codon 15 were present in all subjects detected to be mutant hetero of homo-zygous by RFLP. There was no relationship between the presence of the variant LH and the clinical and hormonal parameter in the PCOS subjects; however, in the controls the presence of the variant LH was associated with a higher serum total testosterone (P = 0.046), oestradiol (P = 0.03) and SHBG (P = 0.002).

CONCLUSIONS

The results of this study show that the variant LH beta-subunit is a common polymorphism occurring in 15% of a healthy UK population of women. The prevalence was not higher in women with PCOS, though it was over represented in obese women with PCOS. The presence of the variant did not alter the clinical or hormonal expression of the disorder in women with PCOS. Its presence in the controls was however associated with higher serum oestradiol and probably secondary elevation of SHBG and testosterone, suggesting that the variant form of LH may be associated with subtle changes in the function of the hypothalamic-pituitary-gonadal axis.

Which hormone tests for the diagnosis of polycystic ovary syndrome?

OBJECTIVE

To assess the frequency of abnormal values for hormone measurements commonly used in the biochemical diagnosis of polycystic ovary syndrome (PCOS).

DESIGN

Hormone measurements in 63 unselected women with clinical and ultrasound diagnosis of PCOS attending gynaecological and general endocrine clinics in a District General Hospital were compared with those from a group of 20 normal ovulatory controls in the early follicular phase of their cycles.

MEASUREMENTS

Serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), LH/FSH ratio, total testosterone, derived free testosterone, sex hormone binding globulin, androstenedione, and dehydroepiandrosterone (DHEA) were measured by radioimmunoassays. LH and FSH measured by two different assays.

RESULTS

The mean serum LH and LH/FSH ratio were significantly (P less than 0.01) higher in the women with PCOS compared with the normal group, but these two measurements were in the abnormal range for only 35% and 41-44%, respectively. Absolute gonadotrophin values were significantly different using the two assay methods, which employed the same reference preparation as standard. Mean serum total testosterone concentration was significantly higher in the PCOS group and was the most frequently (70%) abnormal biochemical marker for PCOS. Sex hormone binding globulin (SHBG) did not differ significantly between the two groups but showed a negative correlation with body mass index in women with PCOS. The combination of SHBG and testosterone to derive a free testosterone value did not further aid the biochemical diagnosis of PCOS. Androstenedione was significantly higher in the PCOS group than in the control group, with a frequency of 53%. There was no significant difference in DHEA-S between the two groups.

CONCLUSION

When typical ovarian ultrasound appearances plus the clinical features of oligomenorrhea and/or hirsuitism were used to define PCOS total testosterone was the best single hormonal marker of the condition. Testosterone, androstenedione or LH, either alone or in combination, were raised in 86% of women with PCOS and these should be the definitive hormonal tests. Using LH/FSH ratio as a biochemical criterion for diagnosis of PCOS should be abandoned because of its low sensitivity. To be of value the normal range for all hormones should be precisely defined in a group of regularly ovulating women in the early follicular phase of the cycle for the assay used in each laboratory.

Changes of bioactive luteinizing hormone after laparoscopic ovarian cautery in patients with polycystic ovarian syndrome

The serum levels of bioactive luteinizing hormone (LH), immunoreactive LH, follicle-stimulating hormone, androstenedione (A), and testosterone (T) were determined in nine anovulatory women with polycystic ovarian syndrome (PCOS) before and after laparoscopic ovarian cautery. Eight ovulated spontaneously and three conceived after treatment. Before treatment, the mean (+/- SEM) levels of bioactive LH, immunoreactive LH, A, and T were 51.4 +/- 8.6 mIU/mL, 36.0 +/- 4.5 mIU/mL, 1.98 +/- 0.35 ng/mL, and 1.18 +/- 0.13 ng/mL, respectively, which were significantly higher than those of five control women (19.2 +/- 1.6 mIU/mL, 21.4 +/- 1.2 mIU/mL, 0.54 +/- 0.03 ng/mL, 0.28 +/- 0.03 ng/mL). After treatment, the mean levels of these hormones had significantly decreased. Decreases in the levels of these hormones by laparoscopic ovarian cautery in women with PCOS may result in both restoration of the ovulatory cycle and achievement of pregnancy.