Recently, a study on sleep quality in patients with differentiated thyroid cancer was conducted by the Department of Nuclear Medicine, General Surgery and Health Administration of Tianjin General Medical University. The study measured the Pittsburgh Sleep Quality Index (PSQI) in three groups of patients: 162 patients in the first group had total thyroidectomy and subsequent radioiodine treatment for differentiated thyroid cancer, 84 patients in the second group had partial excision of benign thyroid nodules, and 78 patients in the third group from the healthy population were controls. The first group of thyroid cancer patients was found to have higher PSQI scores (7.59 ± 4.21) and worse sleep quality (54.32%); after radioiodine treatment, the PSQI scores and the rate of poor sleep quality increased significantly, 8.78 ± 4.72 and 70.99%, respectively. The first group of thyroid cancer patients was studied in two subgroups according to metastasis and it was found that patients with metastatic thyroid cancer (87/162 cases, 53.70%) had higher PSQI scores (10.87 ± 5.18) and a higher rate of poor sleep quality (79.31%). It was concluded that sleep is affected in patients with thyroid cancer and that radioiodine treatment and knowledge of concomitant metastases can affect sleep. Psychological fear of cancer, treatment with nuclear medicine, and metastasis may be larger potential causes, and there is a need for interventional studies on this.