with the exception of certain conditions the treatment of hypothyroidism requires lifelong therapy. before synthetic levothyroxine (t4) was available desiccated thyroid tablets were used. desiccated thyroid was obtained from animal thyroid glands which lacked consistency of potency from batch to batch. presently a pure synthetic t4 is widely available. therefore there is no reason to use desiccated thyroid extract. the most active thyroid hormone is actually t3. so why do physicians choose to treat patients with the t4 form of thyroid? t3 [liothyronine sodium (cytomel)] is available and there are certain indications for its use. however for the majority of patients a form of t4 [levothyroxine sodium (levoxyl synthroid)] is the preferred treatment. this is a more stable form of thyroid hormone and requires once a day dosing whereas t3 is much shorter-acting and needs to be taken multiple times a day. in the overwhelming majority of patients synthetic t4 is readily and steadily converted to t3 naturally in the bloodstream and this conversion is appropriately regulated by the body's tissues. in young healthy patients the full amount of t4 replacement hormone may be started initially. in patients with pre-existing heart disease this method of thyroid replacement may aggravate the underlying heart condition in about 20% of cases. in older patients without known heart disease starting with a full dose of thyroid replacement may result in uncovering heart disease resulting in chest pain or a heart attack. for this reason patients with a history of heart disease or those suspected of being at high risk are started with lower amounts of replacement hormone with a gradual increase in the dose at six-week intervals. ideally synthetic t4 replacement should be taken in the morning 30 minutes before eating. other medications containing iron or antacids should be avoided because they interfere with absorption. therapy for hypothyroidism is monitored at approximately six-week intervals until the patient is stable. during these visits a blood sample is checked for tsh to determine if the appropriate amount of thyroid replacement is being given. the goal is to maintain the tsh within normal limits. depending on the lab used the absolute values may vary but in general a normal tsh range is between 0. 5 to 5. 0 uiu/ml. once stable the tsh can be checked yearly. overtreating hypothyroidism with excessive thyroid medication is potentially harmful and can cause problems with heart palpitations and blood pressure control and can also contribute to osteoporosis. every effort should be made to keep the tsh within the normal range.
how is hypothyroidism treated?