Associations of menstrual cycle irregularities with age, obesity and phenotype in patients with polycystic ovary syndrome

INTRODUCTION

Polycystic ovary syndrome is the commonest endocrine disorder in women of reproductive age and the leading cause of anovulatory infertility.¹ However, PCOS is a heterogeneous disorder and not all women with PCOS are anovulatory.^1,2 Indeed, according to the European Society for Human Reproduction and Embryology (ESHRE) and the American Society for Reproductive Medicine (ASRM) definition of PCOS, at least two of the following three features should be present to establish the diagnosis of PCOS: a) oligo- or anovulation, b) biochemical hyperandrogenemia or clinical manifestations of hyperandrogenemia and c) polycystic ovaries on ultrasound, resulting in four different PCOS phenotypes.² Therefore, ovulatory women with hyperandrogenemia and polycystic ovaries (phenotype 3) are considered to suffer from PCOS.² However, it is unclear whether the severity of menstrual cycle irregularity, a surrogate marker of anovulation, differs between the three different anovulatory PCOS phenotypes.

Small retrospective studies reported a restoration of ovulation with ageing in women with PCOS.^3-5 However, none of these studies described in detail the menstrual cycle pattern in different age groups of PCOS patients.^3-5 In addition, women with PCOS are frequently obese¹ and obesity is associated with menstrual cycle abnormalities in the general population.^6-8 On the other hand, studies in women with PCOS yielded contradictory results regarding the relationship between obesity and menstrual cycle pattern.^4,9-12

We aimed to assess in a large population of women with PCOS the association between menstrual cycle pattern and age, obesity and PCOS phenotype.

PATIENTS AND METHODS

Patients

We studied 1,297 women with PCOS [age 24.3±5.8 years, body mass index (BMI)]. Diagnosis of PCOS was based on the revised Rotterdam criteria, which require the presence of at least two of the following three features: a) oligo- or anovulation (<8 spontaneous hemorrhagic episodes/yr), b) biochemical hyperandrogenemia (defined in our population as early follicular phase testosterone >60 ng/dl, corresponding to the mean+2 SD testosterone levels in 200 control subjects measured in our laboratory) or clinical manifestations of hyperandrogenemia (Ferriman-Gallwey score ≥8) and c) polycystic ovaries on ultrasound (≥12 small follicles in at least one ovary and/or ovarian volume >10cm³).²

None of the women studied had galactorrhea or any endocrine or systemic disease that could possibly affect reproductive physiology. No woman reported use during the last semester of any medication that could interfere with the normal function of the hypothalamic-pituitary-gonadal axis. When basic 17α-hydroxyprogesterone (17α-OHP) levels were >1.5 ng/ml, the Synacthen test (0.25 mg/1ml; Novartis Pharma S.A., Rueil-Malmaison, France) was performed to rule out congenital adrenal hyperplasia. Other causes of hyperandrogenemia, including prolactinoma, Cushing’s syndrome and androgen secreting tumors were also excluded.

Study protocol

In all women, weight, height, waist circumference (W) and hip circumference (H) were measured. Body weight was measured with an analog scale and in light clothing; height was measured barefoot with a stadiometer. The BMI was calculated by dividing weight (in kg) by height squared (in m) to assess obesity. The W was obtained as the smallest circumference at the level of the umbilicus and the H was measured at the level of the widest diameter around the buttocks. The W to H ratio (W/H) was calculated by dividing W by H.

Baseline blood samples were collected between days 3 and 7 of the menstrual cycle in women with regular menstrual cycles and after a spontaneous bleeding episode in women with menstrual cycle abnormalities, after an overnight fast. The circulating levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), total testosterone (T), Δ₄-androstenedione (Δ₄-A), dehydroepiandrosterone sulfate (DHEA-S), 17α-OHP, sex hormone-binding globulin (SHBG), glucose and insulin were measured. Immediately after baseline blood sampling, an oral glucose tolerance test (OGTT) was performed; 75 g of glucose were administered orally and serum glucose levels were determined after 30, 60, 90 and 120 min. On the same day, transvaginal ultrasonography was performed and the volume of each ovary was determined as well as the number of small follicles (measuring 2-9 mm in diameter) in each ovary.

The study population was divided according to: a) age ≤20 years old (n=381), 21-30 years old (n=717) and >30 years old (n=199), b) BMI in normal weight (i.e. with BMI <25 kg/m²; n=679), overweight (i.e. with ΒΜΙ 25-29.9 kg/m²; n=277) and obese (i.e. with BMI ≥30 kg/m²; n=341), c) W in women with and without abdominal obesity [i.e. with W ≥ or <80 cm (n=652 and n=645, respectively) or with W ≥ or <88 cm (n=431 and n=866, respectively)] and d) PCOS phenotype in women with phenotype 1 (i.e. with oligo- or anovulation, hyperandrogenism and polycystic ovaries; n=653), phenotype 2 (i.e. with oligo- or anovulation and hyperandrogenism but without polycystic ovaries; n=408), phenotype 3 (i.e. with hyperandrogenism and polycystic ovaries but without oligo- or anovulation; n=131) and phenotype 4 (i.e. with oligo- or anovulation and polycystic ovaries but without hyperandrogenism; n=105).²

The pattern of menstrual cycles was divided as described previously¹³ into: a) single cycle irregularities (primary amenorrhea, secondary amenorrhea, oligomenorrhea, polymenorrhea; n=148), b) multiple cycle irregularities (secondary amenorrhea alternating with oligomenorrhea, secondary amenorrhea alternating with polymenorrhea, oligomenorrhea alternating with polymenorrhea; n=254), c) regular menstrual cycles alternating with a single cycle irregularity (secondary amenorrhea, oligomenorrhea or polymenorrhea; n=764) and d) regular menstrual cycles (n=131). Primary amenorrhea was defined as absence of menstruation by the age of 16 years. Secondary amenorrhea was defined as absence of vaginal bleeding for at least six months after a period of established menstruation. Oligomenorrhea was defined as cycle length >35 days or <8 cycles/year. Polymenorrhea was defined as cycle length ≤21 days. Regular menstrual cycles were defined as cycle length 28±4 days.

Methods

Serum FSH, LH, PRL, androgen, 17α-OHP, SHBG, glucose and insulin levels were measured as previously described.¹⁴ Free androgen index (FAI) was determined as follows: FAI = T (nmol/l) x 100 / SHBG (nmol/l).¹⁵ The homeostasis model assessment of insulin resistance (HOMA-IR) index was calculated as follows: HOMA-IR = fasting insulin (μIU/ml) x fasting glucose (mg/dl) / 405.¹⁶ The quantitative insulin sensitivity check index (QUICKI) was calculated according to the following formula: QUICKI = 1 / [logInsulin (μIU/ml) + logGlucose (mg/dl)].¹⁷

Transvaginal ultrasonography

Transvaginal ultrasound scans of the ovaries were performed in all women by an experienced sonographer. Ovarian volume was calculated by the formula: V = (π/6) × D_length x D_width × D_thickness, where D is dimension. The presence of polycystic ovaries was diagnosed by the presence of 12 or more follicles in each ovary measuring 2-9 mm in diameter and/or increased ovarian volume (>10 cm³).

Statistical analysis

Data analysis was performed with the statistical package SPSS (version 17.0; SPSS Inc., Chicago, IL). Data are reported as mean±SD. Differences in the prevalence of the different patterns of menstrual cycles between age and BMI groups and between PCOS phenotypes were assessed with the chi-square test. Differences in anthropometric characteristics between women with different patterns of menstrual cycles were assessed with one-way analysis of variance via the Holm-Sidak method for multiple comparison testing. In all cases, a pvalue <0.05 was considered significant.

RESULTS

The age of women with different patterns of menstrual cycles is shown in Table 1. Women with either single or multiple cycle irregularities and no regular cycles were younger than women with regular cycles (23.2±6.6, 23.7±5.5 and 25.7±5.7 years-old, respectively; p=0.001 and p=0.007, respectively). The prevalence of the different patterns of menstrual cycle in the different age groups is shown in Table 2. The proportion of women who had regular menstrual cycles progressively increased in the older age groups, being 8.1, 10.5 and 12.7% in women ≤20, 21-30 and >30 years-old, respectively (p=0.037). In addition, among women with irregular menstrual cycles, the proportion of women who had “milder” cycle abnormalities (i.e. regular cycles alternating with a cycle irregularity) also increased with ageing, whereas the proportion of women who had more “severe” cycle abnormalities (i.e. either single or multiple cycle irregularities and no regular cycles) declined (Table 2).

The anthropometric characteristics of women with different patterns of menstrual cycles are shown in Table 1. The BMI and W did not differ between groups. The prevalence of the different patterns of menstrual cycles in the different BMI groups is shown in Table 3. The proportion of women with regular menstrual cycles did not differ between normal weight and obese women but was higher in overweight women (9.3, 9.4 and 13%, respectively; p = 0.020). Moreover, among women with irregular menstrual cycles, the proportion of women with regular cycles alternating with a cycle irregularity did not differ between normal weight and obese women but was higher in overweight women (58.3, 56.5 and 63.5%, respectively; p = 0.020). The prevalence of the different patterns of menstrual cycles did not differ between women with abdominal obesity and those without abdominal obesity, regardless of the cut-off value of W used for defining abdominal obesity (i.e. ≥80 cm or ≥88 cm; Table 4).

All women with phenotype 3 had regular cycles and were thus excluded from the analysis of the association between PCOS phenotype and the pattern of menstrual cycle. The anthropometric characteristics of women with phenotypes 1, 2 and 4 are shown in Table 5. Women with phenotype 1 were younger than both women with phenotype 2 and women with phenotype 4 (23.5±5.3, 24.6±6.2 and 26.1±6.4 years-old, respectively; p=0.008 and p <0.001, respectively), whereas the latter two phenotypes did not differ in age. On the other hand, women with phenotype 1 and women with phenotype 2 had comparable BMI (26.9±7 and 27.2±7.4 kg/m², respectively) and both had higher BMI than women with phenotype 4 (24.5±6.1 kg/m²; p = 0.004 and p = 0.002 compared with women with phenotype 1 and 2, respectively). The prevalence of the different patterns of menstrual cycles in phenotypes 1, 2 and 4 is shown in Table 6. None of the women with these phenotypes had persistently regular cycles. However, the proportion of women with regular cycles alternating with irregular cycles was highest in women with phenotype 4, intermediate in women with phenotype 2 and lowest in women with phenotype 1 (74.3, 69.4 and 61.7%, respectively; p = 0.027).

DISCUSSION

We report a normalization of menstrual cycles with ageing in patients with PCOS. Indeed, the proportion of patients with regular cycles – either alone or in combination with irregular cycles – increased in older subjects, whereas the proportion of patients without any regular cycles declined. Previous retrospective studies reported spontaneous restitution of cyclic regularity with ageing in women with PCOS but were considerably smaller (n = 33, 205 and 254, respectively), evaluated women of a shorter age range (>40 years, >30 years and 25-31 years, respectively) and did not report in detail the menstrual cycle pattern.^3-5 Other small studies (n = 118 and 204, respectively) focused only on patients with PCOS and a single cycle irregularity and also reported that patients with regular menstrual cycles were older than patients with either amenorrhea or oligomenorrhea.^11,12 It is possible that the progressive decline in circulating androgens or follicle loss with age in patients with PCOS contributes to this progressive improvement in menstrual cycle abnormalities.^5,18-20

Studies in the general population showed that obesity is associated with irregular menstrual cycles.^6-8 Interestingly, the proportion of women with regular menstrual cycles did not differ between normal weight and obese women or between women with and without abdominal obesity in our study. On the other hand, overweight women more frequently presented with regular menstrual cycles. Previous smaller studies in patients with PCOS reported discrepant results regarding the relationship between obesity and menstrual cycle abnormalities. Some investigators reported higher rates of menstrual disorders in overweight/obese patients,^9,10,12 others did not identify differences in BMI between women with amenorrhea, oligomenorrhea and regular menstrual cycles¹¹ and in other reports women with regular cycles were more obese than those with irregular cycles.⁴ On the other hand, diet-induced weight loss in patients with PCOS results in resumption of ovulation,^21-23 while hyperandrogenemia and IR, both of which contribute to anovulation, are more severe in overweight/obese patients with PCOS.^9,24-26 Therefore, obesity appears to have an adverse effect on reproductive function in patients with PCOS, but this effect might be less pronounced than in the general population, possibly because of the overwhelming effects of hyperandrogenemia.

The proportion of women with milder cycle abnormalities (i.e. with some regular cycles alternating with irregular cycles) was highest in women with phenotype 4, intermediate in women with phenotype 2 and lowest in women with phenotype 1. We are not aware of any previous studies that compared menstrual cycle patterns between the anovulatory phenotypes of PCOS. Women with phenotype 1 were younger than women with phenotypes 2 and 3 and this might have contributed to the more irregular cycle pattern in phenotype 1. In addition, women with phenotype 1 have higher serum androgen levels and more severe IR than women with phenotype 2^27-29 and both these phenotypes have by definition more pronounced hyperandrogenemia than women with phenotype 4. Finally, the higher BMI in women with phenotypes 1 and 2 than in women with phenotype 4 might also have played a role in the higher prevalence of abnormal cycles in the former phenotypes.

In conclusion, menstrual cycle pattern is more irregular in women with the “classic” PCOS phenotypes than in phenotype 4 but appears to normalize with ageing. On the other hand, obesity does not appear to have an important effect on menstrual cycle pattern in PCOS. Given the association between irregular menstrual cycles and increased risk for both type 2 diabetes mellitus and cardiovascular events,^30-32 cardiovascular prevention measures should primarily focus on women with the classic PCOS phenotypes and on ageing women with persistently irregular cycles.

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Received: 28-07-2013, Accepted: 05-11-2013