Agents for Hypothyroidism

Labs TSH 16.5 mlU/L, BP 110/76 mm Hg, HR 60 beats/min, weight 165 pounds (155 pounds at last visit), delayed deep tendon reflexes. 

Hypothyroidism is a relative deficiency in thyroid hormones. It manifests as a slowing down of all body functions or a decrease in metabolic rate. There are many causes for hypothyroidism, including Hashimoto s thyroiditis, drug-induced, radiation and radioactive iodine, dyshormono-genesis, congenital, and secondary causes (pituitary or 

The treatment of hypothyroidism involves replacing thyroid hormones. Levothyroxine (T ) is the drug of choice. T has a long half-life (7 days), which allows it to be dosed once daily. Older patients, patients with cardiac disease, or those with chronic hypothyroidism should be started at a lower dose. If cardiac symptoms develop, the dose should be reduced. 

Case Conclusion GM began thyroid hormone therapy with T4. Her dose was initiated at the lower-than-recom-mended dose because GM has a history of AF, which may increase her sensitivity to the cardiac effects of T4. GM will return to the clinic in 4 to 6 weeks to assess her thyroid function and symptoms. Symptoms should begin to resolve in 2 to 3 weeks and should disappear by 6 weeks. 

Drug Interactions Various drugs can decrease T absorption. Drugs such as aluminum hydroxide, ferrous sulfate, sucralfate, and calcium carbonate should be separated from T administration by 1 to 2 hours. Bile acid sequestrants (cholestyramine and colestipol) must be separated from T by at least 4 hours and preferably 6 hours. CYP450 enzyme inducing drugs such as phenytoin, carba-mazepine, rifampin, and phenobarbital can increase T requirements. 

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