Methods A randomized clinical trial to placebo (P) or MTF use. Previous fine needle aspiration confirming the diagnosis is necessary to inclusion. Exclusion criteria were: nodules with a predominantly cystic pattern, pregnancy, diabetes, acromegaly, previous use of MTF, levothyroxine, corticoid or any weight loss medication in the past six months, hepatic or cardiac insufficiency, creatinine levels > 1.4 mg/dL and MTF intolerance doses >1.0 gram/day. Patients will receive similar tablets of MTF and placebo and will be instructed to take 3 tablets/day of MTF (500mg/tablet). Thyroid volume, as TN volume, will be accessed by ultrasound, both in the beginning, six months and one year after randomization, by the same researcher blinded regarding location group. Blood samples to measure: TSH, FT4, TPO-Ab, lipid profile, glucose and insulin were done after 8h fasting.