For patients with thyroid enlargement (goiter) or hypothyroidism, thyroid hormone therapy is clearly needed, since proper dosage corrects any symptoms due to thyroid hormone deficiency and may decrease the goiter's size. Treatment consists of taking a single daily tablet of levothyroxine. Older patients who may have underlying heart disease are usually started on a low dose and gradually increased, while younger healthy patients can be started on full replacement doses at once. Thyroid hormone acts very slowly in the body, so it may take several months after treatment is started to notice improvement in symptoms or goiter shrinkage. Because of the generally permanent and often progressive nature of Hashimoto's thyroiditis, it is usually necessary to treat it throughout one's lifetime and to realize that medicine dose requirements may have to be adjusted from time to time.
Optimal adjustment of thyroid hormone dosage, based on laboratory tests rather than symptoms, is critical, since the body is very sensitive to even small changes in thyroid hormone levels. The tablets come in 12 different strengths, and it is essential to take them in a consistent manner every day. If the dose is not adequate, the thyroid gland may continue to enlarge and symptoms of hypothyroidism will persist. This may be associated with increased serum cholesterol levels, possibly increasing the risk for atherosclerosis and heart disease. If the dose is too strong, it can cause symptoms of hyperthyroidism, creating excessive strain on the heart and an increased risk of developing osteoporosis.