Euthyrox® 100 µg contains levothyroxine sodium, a synthetic form of the thyroid hormone used to treat hypothyroidism (underactive thyroid). It works by replacing or supplementing the thyroid hormone that the thyroid gland is unable to produce in sufficient quantities. This helps to regulate the body's metabolism, energy levels, and overall functioning. Euthyrox® is typically prescribed to manage symptoms of hypothyroidism, such as fatigue, weight gain, and depression. The dosage of 100 µg is used to help maintain normal thyroid hormone levels, and it should be taken as directed by a healthcare provider to ensure proper thyroid function. Regular monitoring of thyroid levels is important while using this medication.