This observational case-control study aims to develop a multidimensional risk assessment model for thrombophilia-related abnormalities in females with polycystic ovary syndrome (PCOS). The study will analyze endocrine, metabolic, and genetic factors associated with decreased protein C and/or protein S levels in participants with PCOS. The results are expected to provide evidence for risk stratification and individualized management in this population.

Polycystic ovary syndrome (PCOS) is a common endocrine disorder in females of reproductive age and is frequently associated with metabolic dysfunction and an increased risk of thrombosis. This study is designed as an observational case-control study to investigate multidimensional risk factors associated with thrombophilia-related abnormalities in females with PCOS.

Female participants aged 14 to 45 years will be enrolled. Adult participants will be diagnosed with PCOS according to the 2023 international evidence-based guideline. After exclusion of related disorders, diagnosis in adults is based on ovulatory dysfunction and/or irregular menstrual cycles together with clinical hyperandrogenism, biochemical hyperandrogenism, or polycystic ovarian morphology on ultrasound where appropriate. Adolescent participants will be diagnosed according to adolescent-specific recommendations. After exclusion of related disorders, both ovulatory dysfunction and/or irregular menstrual cycles and clinical or biochemical hyperandrogenism are required. Polycystic ovarian morphology alone will not be used to diagnose PCOS in adolescents.

Participants will be classified into a case group and a control group according to the presence or absence of decreased protein C and/or protein S levels. Endocrine, metabolic, and genetic variables will be collected and analyzed. Statistical analyses will include descriptive analysis, group comparisons, univariable analysis, multivariable logistic regression, and model performance evaluation using receiver operating characteristic curves and the area under the curve.

The primary outcome is decreased protein C and/or protein S levels at baseline. The goal of this study is to construct a multidimensional risk assessment model for thrombophilia-related abnormalities in females with PCOS and to provide evidence for risk stratification and individualized management.

Inclusion Criteria:

• Female participants aged 14 to 45 years
• Diagnosis of polycystic ovary syndrome (PCOS)
• For adult participants, PCOS diagnosed according to the 2023 international evidence-based guideline. After exclusion of related disorders, diagnosis is based on ovulatory dysfunction and/or irregular menstrual cycles together with clinical hyperandrogenism, biochemical hyperandrogenism, or polycystic ovarian morphology on ultrasound where appropriate
• For adolescent participants, PCOS diagnosed according to adolescent-specific recommendations. After exclusion of related disorders, both ovulatory dysfunction and/or irregular menstrual cycles and clinical or biochemical hyperandrogenism are required
• Irregular menstrual cycles are defined as follows: more than 1 year and less than 3 years after menarche, menstrual cycles shorter than 21 days or longer than 45 days; more than 3 years after menarche to perimenopause, menstrual cycles shorter than 21 days or longer than 35 days, or fewer than 8 cycles per year; any cycle longer than 90 days more than 1 year after menarche; or primary amenorrhea by age 15 years or more than 3 years after thelarche
• No use within 3 months before blood sampling of anticoagulant drugs, procoagulant drugs, oral contraceptives, or other medications that may affect sex hormones, insulin, glucose metabolism, or coagulation function

Exclusion Criteria:

• Confirmed pregnancy
• Hematologic disease
• History of malignant tumor
• Use of medications within 12 weeks before enrollment that may interfere with study assessments
• Disorders that may cause hyperandrogenism or ovulatory dysfunction, including congenital adrenal hyperplasia, Cushing syndrome, functional hypothalamic amenorrhea, thyroid disease, hyperprolactinemia, or primary ovarian insufficiency
• Disorders that may affect protein C or protein S levels, including antiphospholipid syndrome, liver disease, or tumor-related conditions
• In adolescents, polycystic ovarian morphology alone will not be used to establish the diagnosis of PCOS

Female participants aged 14 to 45 years with polycystic ovary syndrome will be enrolled. Participants will be classified according to the presence or absence of decreased protein C and/or protein S levels.