Patients and methods
hypothyroid, kidney or liver disease, cancer
HYPOTHYROID, CANCER, CONGESTIVE HEART FAILURE
The study was conducted at the Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran, from January 1, 2022 to 31 June, 2022. Radioiodine-treated hypothyroid patients over 20 years of age, who attained euthyroid status with LT4 monotherapy and serum TSH concentration of 0.5-5 mU/L were recruited from the Endocrine Clinic and referred to the Research Institute for Endocrine Sciences (RIES). The patients with pregnancy, chronic kidney or liver disease, congestive heart failure, cancer, and those taking methimazole, propylthiouracil (PTU), tamoxifen, estrogen, progesterone, and corticosteroids were excluded. Dorsa Pharmaceutical Company and Tavan Institute formulated sustained-release tablets with 7.5, 9 and 12 µg potency.A parallel randomized controlled clinical trial was applied. Initially, the patients were allocated to the three intervention and one control groups. Intervention groups received three different combinations of LT4 + LT3 yielding ratios of 1:10 (75 µg LT4 + 7.5 µg SR-T3), 1:7.5(9 µg SR-T3 + 68.5 µg LT4) and 1:5 (12 µg SR-T3 + 60 µg LT4). As during follow-up, serum TSH concentration significantly increased in the patients who received 75 µg LT4 + 7.5 µg SR-T3, this group were excluded from the study. Therefore, trial groups in this survey consisted of group A with a daily intake of 9 µg SR-T3 plus 68.5 µg LT4 (ratio 1:7.5), group B with a daily intake of 12 µg SR-T3 plus 60 µg LT4 (ratio 1:5) and a control group with LT4 monotherapy (group C).Figure 
Participants’ flow-diagramAt the baseline visit, after taking informed written consent, blood pressure, weight, and height were measured. The trained staff filled the questionnaire regarding demographic and thyroid symptoms. Patients were allocated to three intervention groups and one control group using stratified randomization. Two stratifications were made based on gender. Under each sex subgroup, patients were randomly assigned to three treatment groups using the random table allocation.After implementation of randomization and specific coding, the subjects were assigned to two intervention and one control groups using allocation concealment. The standard method of ensuring allocation concealment was sequentially numbered. The staff member not involved in the trial was instructed to keep the list private and only revealed a treatment allocation after receiving information showing that the patient is eligible and has consented to the trial. The patients and the investigators were kept from knowing who was assigned to which treatment. All groups received identical tablets in physical appearance, taste, and smell to fulfill blinding.The participants were evaluated at baseline and two consequent follow-ups on the 8