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Treatment of Hypothyroidism

This is an overview of the medical treatment of low thyroid function


Thyroxine (T4) and tri-iodothyronine (T3) are the two major types of thyroid hormones that the body makes. These compounds are available in pill form, have few side effects if taken properly, and are inexpensive. "Levothyroxine" is the generic name for T4 thyroid replacement, but there are many different formulations. Liothyronine is the generic name for T3 thyroid replacement. Levothyroxine is a very stable medication whose half-life is about 7 days, so it can be taken once a day. Liothyronine is usually taken once or twice per day since its half-life is shorter.  The role of iodine supplementation, dietary supplements, and nutraceuticals is not completely clear. Read more to find out the answer to this commonly asked question.

The manner in which these medications are taken greatly affects how much actually is absorbed into the blood. It is important to take the medication with water, on an empty stomach , at least 4 hours away from certain medications, and to wait at least 30-60 minutes before eating. These thyroid replacement pills are well absorbed from the gastrointestinal system so once a patient is on the correct dose and taking it properly, only intermittent blood testing is adequate. 
Ten percent of hypothyroid patients require unexpectedly high doses of hormone and the most common cause is non compliance with the medication.  If normalization of the TSH is not easily achieved or very high doses of medication are needed, your endocrinologist may begin a workup for causes of gastrointestinal malabsorption (celiac disease, parietal cell antibodies, helicobacter pylori, lactose intolerance, bacterial infections, etc). (1,2,3) 
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The goal of treatment is to bring the TSH to a normal range over period of time determined by a patient's age and other medical conditions. If a patient previously had thyroidectomy for thyroid cancer, the goal of treatment is usually to suppress the TSH to much lower levels. Patients with well-treated hypothyroidism should live otherwise normal and healthy lives. 

Long term treatment with thyroxine medication when properly monitored, is generally very safe with no significant increase in morbidity or mortality. 
Thyroxine (T4) treatment reduces the TSH. When the TSH is lowered too much there is an association with detrimental effects on the heart and the bones. These risks occur in patients taking any form of thyroid hormone: desiccated, "bio-identical", compounded, or synthetic thyroid hormone replacement.   A TSH value of less than or equal to 0.1 mU/l has been identified as a risk factor for the development of atrial fibrillation (13). Atrial fibrillation is an abnormal heart rhythm which can cause strokes. Long term thyroxine therapy to TSH-suppressive doses may cause the heart to become enlarged and increases the risk of ischemic heart disease in patients under the age of 65 years. TSH-suppressive doses of levothyroxine have been associated with bone loss in some but not all studies. A meta-analysis (compilation of many scientific studies) concluded that bone mineral density was reduced in hypothyroid patients with a suppressed TSH due to excessive levothyroxine therapy in postmenopausal women. This suggests an increase risk for fracture but this is not conclusive since no or a minimal excess of bone fractures has been observed in patients on levothyroxine even if TSH is suppressed. Cardiovascular disease, dysrhythmias, and fractures were increased in patients with a high TSH (>4.0 mU/l) and especially in patients with a suppressed TSH (< or = 0.03 mU/l) when compared to patients with a TSH in the laboratory reference range. (19)  In a linked nested case-control study of 213,511 patients over the age of 70 who were taking levothyroxine for primary hypothyroidism (BMJ April 28, 2011), Turner et al. report that current use of thyroxine was associated with a significantly increased risk of fracture (adjusted odds ratio 1.88, 95% confidence interval 1.71 to 2.05) compared with use in the remote past. The risk of fracture was closely associated with the dose of thyroxine. In other studies, all age groups were shown to have an increased fracture risk if TSH values were suppressed and there was an increased risk of heart disease as patients age if the hormone levels are too high . Overall age and hormone levels together should help guide proper treatment to prevent harm in the long term. 
  


References:
Checchi S, Montanaro A, Ciuoli C, et al. Prevalence  of parietal cell antibodies in a large cohort of patients with autoimmune thyroiditis. Thyroid 2010;20:1385-9. Epub November 7, 2010.
2. Bugdaci MS, Zuhur SS, Sokmen M, et al. The role of Helicobacter pylori in patients with hypothyroidism in whom could not be achieved (sic) normal thyrotropin levels despite treatment with high doses of thyroxine. Helicobacter 
2011;16:124-30.
3. Atypical celiac disease as cause of increased need for thyroxine: a systematic study . J Clin Endocrinol Metab . January 11, 2012