T4/T3 Therapy in Hypothyroidism

.Participants will

• Take LT4+LT3 or LT4+placebo for 6 months
• Visit the clinic at the beginning and the end of the study for a blood test and to answer questionnaires.
• Have blood tests checked at 6 and 13 weeks and symptom checks by text (weekly to monthly)

Inclusion criteria

• Male or female, aged 18-70 years
• Hypothyroidism due to either thyroid failure or total thyroidectomy for structural thyroid disease (nodules, benign goiter, or thyroid cancer) for at least 6 months
• Taking 75-150 mcg per day LT4 and a minimum of 1.2 mcg/kg/day, with stable dose of LT4 for at least 3 months prior to enrollment
• TSH of 0.5 to 4.0 mU/L within 2 months of enrollment
• Persistent symptoms for at least 2 months, and a TSQ score of ≥ 5
• For females of reproductive potential: use of highly effective contraception for at least 1 month prior to screening and agreement to use such a method during study participation and for an additional 4 weeks after the end of study intervention.

Exclusion criteria

• Current use of LT3, thyroid extracts, Tirosint liquid or capsules, amiodarone, lithium, methimazole, propylthiouracil, supraphysiologic doses of corticosteroids, immunotherapy, tyrosine kinase inhibitors, interferon, or biotin supplements
• Diseases of the pituitary or hypothalamus
• History of thyroid cancer requiring suppression of TSH secretion
• Unstable cardiac conditions, including uncontrolled hypertension (current blood pressure greater than 160/100), arrhythmia, or angina
• Uncontrolled psychiatric disorders
• Pregnancy or lactation, or planned pregnancy within the next 7 months
• History of food dye allergies
• GFR <30 ml/min/1.73 m2
• Other conditions which, in the opinion of the investigators, would prevent them from participating in the full duration of the study (for example, end-stage cancer)