1 Institute of Endocrinology, Národní 8, Prague 1, 116 94 Czech Republic, 2 Department of Obstetrics and Gynecology, Charles University, Apolinárská 28, Prague 2, 120 00 Czech Republic and 3 Department of Internal Medicine, Charles University, U Nemocnice 1, Prague 2, 120 00 Czech Republic
Dr Gustav
indelka died in 2001.
4 To whom correspondence should be addressed. E-mail: jvrbikova{at}endo.cz
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Abstract |
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Key words: euglycaemic clamp/insulin resistance/metabolic syndrome/polycystic ovary
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Introduction |
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On the other hand, a surprisingly low number of women with metabolic syndrome have been shown to be affected by PCOS (Korhonen et al., 2001). To date there are few data concerning the prevalence of metabolic syndrome in PCOS women, and these data are mainly derived from the US population (Glueck et al., 2003; Apridonidze et al., 2005
), where significantly more women are obese in comparison with European studies.
The authors evaluated a group of young women with PCOS in comparison with age-matched healthy women for the occurrence of various features of metabolic syndrome according to ATP III. A second aim was to describe the mutual relationship of different features of metabolic syndrome to insulin resistance, as examined by euglycaemic hyperinsulinaemic clamp.
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Materials and methods |
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The control group consisted of 73 healthy, age-matched females recruited by advertisement, all of whom were in good health with no serious disorders, with a regular menstrual cycle (2135 days), with no clinical signs of hyperandrogenism and with serum testosterone lower than 2.65 nmol/l. Pelvic ultrasonography was not performed. The patients used no medication.
The local ethics committee of the Institute of Endocrinology approved the protocol of the study and all the patients and controls signed informed consent before the examinations.
The patients and controls were evaluated at the clinical department of the Institute of Endocrinology as outpatients. Two blood pressure readings were obtained in sitting patients after a 10-min rest; the mean was determined from two values and was used for further analysis. Waist circumference was measured in the standing position, halfway between the lower ribs and the crest of the pelvis. Blood sampling for hormonal and biochemical examination was done between days 3 and 6 of the menstrual cycle or, in the case of secondary amenorrhoea, at any time.
Metabolic syndrome was defined using the ATP III criteria (1997), as the presence of three or more of the following features: (i) abdominal obesity (waist circumference >88 cm); (ii) hypertriglyceridaemia (>1.69 mmol/l); (iii) decrease in high-density lipoprotein (HDL) cholesterol (<1.29 mmol/l); (iv) high blood pressure (130/85 mmHg); (v) high fasting blood glucose (
6.1 mmol/l).
In PCOS patients, after basal blood samples were taken, a 2-h euglycaemic hyperinsulinaemic (1 mIU kg1 min1) clamp was performed as described previously (DeFronzo et al., 1979). Insulin sensitivity was determined from the values obtained during the steady-state period, between the 100th and 120th minutes. The target blood glucose level was 5.0 mmol/l, with the coefficient of variance less than 5%. The glucose disposal rate, defined as the amount of glucose supplied by the infusion to maintain the desired blood glucose level (µmol kg1 min1), and the insulin sensitivity index (ISI), defined as the ratio of the glucose disposal rate to the average insulin concentration during the observed period (ISI, µmol kg1 min1 per mIU l1 x 100), were calculated on the basis of the clamp results.
Blood glucose was determined in the whole blood by the electrochemical method (Super GL, Dr Muller Gerate Bau, GmBH, Freital Germany). Insulin was estimated by immunoradiometric assay using an immunoradiometric assay kit (Immunotech, Marseilles, France). Total cholesterol, HDL cholesterol and triglycerides were assessed by photometry (Ecoline 25; Merck Vitalab Eclipse, Darmstadt, Germany). Testosterone, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulphate, LH and sex hormone binding globulin were determined as described previously (Vrbikova et al., 2001).
Statistical evaluation
After confirming a Gaussian distribution, Students t-test was used to evaluate differences between the controls and the PCOS women. Results are presented as mean ± SD. The 2 test or Fishers exact test was used to compare the frequencies of the particular features of metabolic syndrome between PCOS women and controls.
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Results |
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The occurrence of the individual features of metabolic syndrome (according to NCEP/ATP III) in PCOS and controls is given in Table II. No significant difference in the occurrence of any of the features of metabolic syndrome was found between Czech PCOS women and the controls. In PCOS women the following combinations were found: reduction of HDL cholesterol with an increase in waist circumference (two patients), and reduction in HDL cholesterol with elevation of triglycerides (two patients). Other possible combinations were not encountered. Overt metabolic syndrome (higher blood pressure with higher triglycerides and lower HDL cholesterol) was found in only one patient.
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To evaluate whether the occurrence of the individual features of metabolic syndrome are different in insulin-sensitive and insulin-resistant PCOS, women were compared on the basis of the degree of insulin sensitivity. Initially, 17 women with ISI below the lower quartile of insulin sensitivity (44.8 µmol kg1 min1 per mIU l1 x 100) were compared with the remaining 52 women. The occurrence of low HDL cholesterol was not significantly different between the groups (33.3 versus 39%), as was also true of abdominal obesity (7 versus 10%,), while arterial hypertension occurred in three women in the lower quartile versus one in the rest. When comparing women above the upper and below the lower quartiles of ISI (ISI >80.8 versus <44.8 µmol kg1 min1 per mIU l1 x 100), isolated features of metabolic syndrome were found in 8/17 women above the upper quartile as opposed to 11/16 women below the lower quartile (P = 0.20; 2 = 1.59.). Women with at least one feature of metabolic syndrome (n = 37) were, in comparison with women free of any of these features (n = 32), significantly more obese (BMI 26.0 ± 5.5 versus 22.3 ± 2.4 kg/m2; P = 0.0001), with lower insulin sensitivity (52.7 ± 28.5 versus 69.6 ± 25.0 µmol kg1 min1 per mIU l1 x 100; P = 0.05) and lower testosterone (3.1 ± 1.1 versus 3.8 ± 1.3 nmnol/l; P = 0.03).
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Discussion |
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In this study, isolated features of metabolic syndrome were much less frequent in young Czech PCOS women than they were in the US population. Czech PCOS data were compared with recently published data from the USA (Apridonidze et al., 2005); it was found that all of the features of metabolic syndrome (with the exception of elevated fasting blood glucose) were significantly more common in the US population than in Czech females.
There is a paucity of data concerning the occurrence of metabolic syndrome in PCOS. A study on the occurrence of metabolic syndrome in women in the USA with PCOS was undertaken in 2003 (Glueck et al., 2003), in which all of the features of metabolic syndrome were found significantly more often in these PCOS women than in the NHANES III white female population; metabolic syndrome was diagnosed in 46% of PCOS women. Recently, a similar study in the US population has confirmed these data; the authors described a prevalence of metabolic syndrome in PCOS women twice as high as that in the general population data (Apridonidze et al., 2005
). These results are different from those of the present study; the US population was slightly older (average age 31 versus 24 years), but this is probably of no great importance. Secondly, and more importantly, the US women were significantly more obese (85% with a waist circumference of over 88 cm or BMI between 31.7 and 42 kg/m2).
Higher BMI, waist circumference and systolic and diastolic blood pressures in PCOS women than in controls have already been described; thus, these results accord with those of other studies (Conway et al., 1992; Talbott et al., 1995
, 1998
,). On the other hand, no elevation of any of these parameters above the upper limit of the normal range (Author: as meant?) was found in PCOS women compared with their healthy counterparts. It may thus be speculated that these subclinical risks worsen over time; contrary to this speculation, there are, however, data finding an equal metabolic risk profile between PCOS and healthy women above 40 years (Talbott et al., 1998
). An alternative explanation might be that only some PCOS women are susceptible to metabolic syndrome and cardiovascular disease. The most significant difference between PCOS women with and without some features of metabolic syndrome was in the degree of obesity, compared with slight differences in insulin sensitivity. Obesity might thus be considered the most important factor aggravating cardiovascular risks in PCOS women, just as it is in the general population (St-Onge et al., 2004
). This speculation is also substantiated by the comparison of data derived from Czech and US women affected with PCOS. Recent studies on metabolic syndrome derived from US data have comprised mostly women with a significant degree of obesity, nearly all of whom have at least one feature of metabolic syndrome, and of whom some 4050% suffered from overt syndrome. By contrast, Czech PCOS women were mostly lean or only slightly overweight.
In individuals participating in the third national health and nutrition examination survey, (NHANES III), the odds of having metabolic syndrome increase with increasing BMI even in the high-normal range (St-Onge et al., 2004). How this translates to end-point cardiovascular events remains to be verified by long-term prospective studies. In terms of the conversion rate from normal glucose tolerance to diabetes, initial obesity (but not a moderate weight gain during the period of a 4- to 7-year follow-up) was a significant determinant of conversion (Wang and Norman, 2004
).
There are some drawbacks to the present study. The control group was defined on the basis of self-reported regular menstrual cyclicity, in connection with normal plasma testosterone and no clinical signs of hyperandrogenism, such as hirsutism, acne or alopecia. Two of the three criteria of the Rotterdam consensus were therefore excluded, but ovarian morphology was not examined. A prevalence of as high as 20% PCO is detected among healthy females (Clayton et al., 1992). On the other hand, females with PCO have been reported as having higher serum testosterone than those with normal ovarian morphology (Adams et al., 2005
). The authors detected no bimodal testosterone distribution, and do not therefore believe that there is a substantial proportion of unrecognized PCOS in the control group. The second drawback lies in the fact that the healthy controls were not taken from a random population sample, but rather were recruited by advertisement. Selection bias could therefore affect the results, and it is difficult to judge whether healthier women are more likely to respond to such an advertisement, or if the opposite is true.
In conclusion, overt metabolic syndrome as defined by NCEP/ATP III is only rarely encountered in young Czech females affected by PCOS. The occurrence of the different features of this syndrome in PCOS is no more frequent than in healthy controls, despite the fact that PCOS women have higher average BMI, waist circumference and systolic and diastolic blood pressures than controls. The most commonly encountered abnormality is decreased HDL cholesterol.
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Acknowledgements |
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References |
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Submitted May 14, 2005; resubmitted June 17, 2005; ; accepted June 29, 2005