Background: This study was designed to assess oral ulcerative mucositis, C-reactive protein, blood pressure, heart rate and thyroid function in breast cancer patients in relation to the occurrence of posttraumatic stress disorder (PTSD). Methods: A total of 120 female breast cancer patients and women 100 healthy subjects were enrolled in this study. PTSD status was assessed by questionnaire. Before and after treatment (modified radical mastectomy and chemotherapy), serum samples were collected and measured for levels of triiodothyronine (T3), thyroxine (T4), thyroid stimulating hormone (TSH) and high-sensitivity C-reactive protein (hs-CRP) by ELISA. Oral ulcerative mucositis was evaluated by the number and duration of oral ulcers and the degree of pain. Results: Breast cancer patients experienced long-term PTSD and had elevated serum T3 and T4 levels. Patients experienced more severe pain and longer duration of oral ulcers compared with the healthy group. Oral ulcers were significantly associated with PTSD score in terms of the number of ulcers (p=0.0025), the degree of pain (p<0.0001) and the duration of ulcers (p<0.0001). Conclusion: These findings support that thyroid function is altered in breast cancer patients with PTSD. Elevation of T3 and T4 and oral ulcerative mucositis might be indicative of the emotional status of breast cancer patients. Copyright © 2013 Wichtig Publishing - Milano (Italy).