IRCT20220307054211N1 IRCT 2022-05-15 Aburaihan pharmaceutical co. Comparison of the hormonal responses to Levothyroxin made by Aburaihan company with Levothyroxine made by Merck company Non-inferiority Randomized Controlled Clinical Trial of the hormonal responses to Levothyroxin made by Aburaihan company and Levothyroxine made by Merck company 2022-07-11 anticipated 60 Complete https://irct.ir/trial/62358 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Not used, Assignment: Parallel, Purpose: Treatment, Other design features: The drug will be continued in 2 intervention groups (Levothyroxine made by Merck and Abureihan companies). Patients will be visited 6 and 8 weeks later to measure TSH and FT4 and assess therapy adherence and adverse effects. Drug dosage would be adjusted to maintain serum TSH concentration within 0.5-3 mU/l. Participants will be evaluated at baseline and two consequent follow-ups at six and eight weeks. At the first, second, and last visit at eight weeks, venous blood samples will be collected from all participants to measure serum TSH and FT4. Thyroid symptom questionnaires (TSQ) and thyroid treatment satisfaction questionnaires(ThyTSQ) will be filled out at the first and last visits (TSQ and ThyTSQ).To ensure compliance with drug therapy, the responsible person will check the drug package and count the number of pills intake by direct questioning in 2 weeks intervals by phone call and pill counting at the last visit, Randomization description: Patients are divided into two intervention groups based on cluster randomization. Six stratifications will be made based on age and gender. At first, patients will be assigned to three age groups of ≤50y, 51-70y, and >70 y. Under each subgroup, patients will be assigned to male and female. Then under each sex subgroup, patients will be randomly assigned to two treatment groups using the random table. Random sequences will be generated using Random-Allocation software, Blinding description: After performing randomization and special coding, subjects are assigned to groups using concealment, which helps keep physicians, participants, and researchers unaware of the type of treatment being assigned. Standard methods will be used to ensure concealment. Opaque containers will be numbered or coded in order. For single-center clinical trials such as the current trial, we select an expert who does not participate in the trial and can maintain a randomized list. This person is instructed to keep the list private and disclose treatment allocation only after receiving information indicating the patient is eligible and has consented to the trial. Subjects and researchers will be protected from knowing who will be assigned to which treatment (double-blind). Both groups will receive the same pills in appearance, taste, and smell. 2 Hypothyroidism. Intervention 1: Intervention group number one: This group will receive Levothyroxine pills made by Merck company. They will take 1.6 micro-gram per kg daily before breakfast for eight weeks. Intervention 2: Intervention group number two: This group will receive Levothyroxine pills made by Abureihan company. They will take1.6 micro-gram per kg daily before breakfast for eight weeks. No - There is not a plan to make this available Justification or reason for not sharing IPD is These data belong to Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences.