Objective In this study, levels of progranulin (PGRN) and tumor necrosis factor-alpha (TNF-alpha) were measured to detect the presence of inflammation in lean polycystic ovary (PCOS) patients. Methods 40 lean PCOS patients were assessed by Rotterdam criteria. Forty healthy women with regular menstrual cycles and without biochemical and clinical hyperandrogenism were involved in our study. Blood samples were taken from the patient and control groups for the measurement of progranulin (PGRN), tumor necrosis factor-alpha (TNF-alpha), lipid parameters, glucose, insulin, and other hormones. Results Serum PGRN and TNF-alpha levels were significantly higher in patients with lean PCOS, compared with the control group (p = .037, p = .041). PGRN levels were positively correlated with TNF-alpha levels in lean PCOS patients. Conclusion PGRN is known as a ligand for the TNF-alpha receptor. PGRN level increase in lean PCOS patients may be due to inhibiting the inflammatory effects of TNF-alpha. To observe the PGRN and TNF-alpha connection in obesity, further study is needed in obese PCOS patients and obese control groups.