Objective: It is thought that sex-specific differences in schizophrenia may be associated with gonadalhormones, especially estrogen. This study aimed to investigate the relationship between follicle stimu lating hormone (FSH), luteinizing hormone (LH), prolactin, estradiol, and progesterone serum levels andsymptom severity during the menstrual cycle in female patients with schizophrenia. Methods: Serum samples were taken in the follicular and periovulatory phases from 32 female patientswith schizophrenia; and FSH, LH, prolactin, estradiol, and progesterone levels were performed. Simulta neously, the patients were administered positive and negative symptom scale (PANSS), Calgary depres sion scale for schizophrenia (CDSS), and Hamilton anxiety rating scale (HAM-A). Results: PANSS (z = -2.52, P < .001), HAM-A (z = -3.60, P < .001), and CDSS (z = -2.52, P = .012) scores werelower in the periovulatory phase than in the follicular phase. Negative correlations between FSH andPANSS positive symptom subscale (r = -0.393, P = .035), and between prolactin and PANSS total score(r = -0.406, P = .029) were detected. Conclusion: Hypoestrogenism should be studied more in patients with schizophrenia. Studies withlarge samples evaluating FSH, LH, prolactin, and progesterone together with estrogen are needed tobe able to safely use gonadal hormones, which may be related to schizophrenia symptom severity,especially in patients who do not respond adequately to treatment.