Synthroid is used to treat hypothyroidism, a condition where thyroid hormones are produced in the thyroid gland in inadequate amounts. Synthroid can help regulate the proper levels of energy and metabolism. For children, having the proper amount of the thyroid gland is vital for physical and mental development. Synthroid is a derived from porcine thyroid glands and has a strong, characteristic. Synthroid contains inactive ingredients: sodium starch glycolate, dextrose, calcium stearate, microcrystalline cellulose, and op-dry white. Synthroid is a natural product made from animal thyroid glands. Synthroid is also used in the treatment of other types of thyroid disorders such as specific types of thyroid cancer, goiters, and also to test for thyroid function. It is also used to treat or prevent certain types of goiters and to manage thyroid cancer. Synthroid is also used for other conditions as determined by your doctor. Synthroid works by replacing or providing more thyroid hormone, which is produced by the thyroid gland. Low thyroid hormone levels naturally occur when radiation/medications injure the thyroid gland or removed by surgery. Having adequate thyroid hormone is essential for maintaining normal mental and physical activity. In children, having enough thyroid hormone is important for normal mental and physical development.