Polycystic ovary syndrome (PCOS) is a prevalent endocrinopathy characterized by insulin resistance, hyperinsulinemia, and increased ovarian androgen production. While obesity has been linked to the pathogenesis of PCOS, the condition is also observed in individuals with normal BMI. This cross-sectional study aimed to evaluate the biochemical profile of lean and obese patients with PCOS. Fifty female patients with previously diagnosed PCOS were included in the study, attending the outpatient clinic at AL-Zahraa Teaching Hospital in Al-Najaf between September 2021 and March 2022. Blood samples were collected from each patient to assess insulin levels, lipid profiles, and fasting blood sugar. The results showed a comparable percentage of lean and obese PCOS patients, with a slightly higher proportion of obese individuals. Statistically significant differences were observed in obese patients with higher fasting blood sugar levels, insulin, HDL cholesterol, and triglycerides. Additionally, the HOMA index, an indicator of insulin resistance, was higher in obese individuals. Lean PCOS patients exhibited metabolic, hormonal, and hematopoietic dysregulations comparable to or less pronounced than those affecting the obese phenotype. Regardless of BMI, insulin resistance is part of PCOS and must be treated immediately.