PCOS is a complex disorder with metabolic and endocrine manifestations and seems to have long term health consequences of the syndrome [
10]. In addition to the diabetes, cardiovascular disease and breast cancer, the effect of the unopposed and uninterrupted estrogenic stimulation is to place the patient at considerable risk for endometrial cancer [
5,
10,
11]. The known factors which increase the risk of developing endometrial hyperplasia and cancer are obesity, nulliparity, infertility, hypertension and diabetes [
12]. Most of these factors are also known to be associated with PCOS [
10]. Therefore, it is important to evaluate the endometrium and recognize the clinical factors that are likely to have affected on endometrial disease in women with PCOS. To our knowledge, this is likely to be the first study to investigate the endometrial histology and find the predictable clinical factors for endometrial disease in Korean women with PCOS. The incidence of endometrial disease in our study was 23.1% of women with PCOS and of these, 21.4% and 1.7% were endometrial hyperplasia and endometrial cancer, respectively. In another study [
8], the endometrial hyperplasia was diagnosed in 35.7% of women with PCOS who were not receiving either contraceptive steroids or periodic or monthly progestin withdrawal. In a long-term follow up study of women with PCOS based on ovarian wedge resection, the odds ratio for endometrial cancer was 5.3 (95% CI, 1.55-18.60) compared with control subjects [
12]. In a larger study of 1,270 women with chronic anovulation, the relative risk of endometrial cancer was identified to be 3.1 (95% CI, 1.1-7.3) and the risk was only significantly increased in the subgroup of overweight women [
13]. Then, the question whether all PCOS patients require an endometrial biopsy to exclude endometrial disease remains unanswered and if so, predictable clinical factors for endometrial disease are questionable. Many authors agree that in postmenopausal women with uterine bleeding, the endometrial thickness on vaginal ultrasound assessment has been positively correlated with the presence of endometrial abnormalities, and curettage can be avoided if the endometrial thickness is less than 4 mm [
14,
15]. In PCOS patients, unfortunately there are no clear clinical guidelines to determine when the endometrial biopsy should be performed [
8]. Cheung [
8] demonstrated that in anovulatory, infertile women with PCOS, endometrial thickness greater than 7 mm or intermenstrual interval of more than 3 months can be associated with endometrial hyperplasia and an endometrial biopsy would be recommended. Other authors propose that endometrial biopsy is indicated when the clinical history suggests long-term unopposed estrogen exposure even when the endometrial thickness is normal (5-12 mm), and that biopsy should be performed when endometrial thickness is greater than 12 mm even when clinical suspicion of disease is low [
6]. In our study, although this study has a limitation that has been not shown an intermenstrual interval or the duration of exposure to unopposed estrogen, the endometrial thickness and age were positively correlated with the presence of endometrial disease in women with PCOS. Also, our study showed that in women with PCOS, endometrial thickness more than 8.5 mm or age more than 25.5 years could be associated with the endometrial disease.
In conclusion, it seems that the endometrium in women with PCOS is different from it of healthy women in the endocrinological aspect, and is consistent with a higher incidence of hyperplasia and cancer [
16]. Theoretically, there are many clinical factors developing endometrial hyperplasia or cancer, but an endometrial biopsy to exclude endometrial disease should be considered according to the clinical status. And also, the results of this study suggest that the age and endometrial thickness may be used as clinical determining factor for endometrial biopsy.