Polycystic ovary syndrome (PCOS) is the most common form of chronic female disease associated with androgen excess; perhaps occurring in 5-10% of the reproductive age group in women. PCOS is viewed as a heterogeneous disorder of multifactorial etiology. It is also associated with increased metabolic and cardiovascular risk factors. Objectives: The purpose of this study is to evaluate the serum level of hormones TSH, T3 and T4 in women with PCOS and to investigate the effect of metformin on hormones TSH, T3, and T4 levels in subjects with PCOS. Patients and methods: The present study was conducted at Kirkuk General Hospital and Azadi General Hospital from March 2023 to January 2024.One hundred forty-one women with PCOS were selected as the PCOS group, while 120 healthy women matched for age with the PCOS patients were selected as the control group. The body mass index is determined before and after therapy. They take metformin 850 mg twice daily for three months and provide fasting blood samples on the second day of menstruation before and after treatment. The data collection done through a designed closed and open-ended questionnaire, by using direct interviewing, and Ultrasound examination, Data were analyzed using SPSS for Windows 7. Results: Treatment resulted in a significant decrease in in body mass index at p-values 0.05. This study reveals that the thyroid hormones TSH, T3 and T4 were highly significantly increased (P < 0.001) in the serum of PCOS patients compared to the control group. Serum levels of TSH in women with PCOS were high significantly elevated compared to healthy control group. However, the study found no significant difference (p > 0.05) in TSH level in treated group with metformin compared with pre-treatment. Conclusion: Metformin can induce changes of TSH levels in patients with polycystic ovary syndrome.