Hypothyroidism is a state of thyroid hypofunction due to different causes and produces as a final state an insufficient synthesis of thyroid hormones.Worldwide, its prevalence is between 1% and 4%.Levothyroxine is the best treatment in hypothyroidism but is a drug with stability problems reported in the literature.The bioequivalence studies are required to establish pharmaceutical equivalents between the different brands of Levothyroxine.