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Definition Return to top
Drug-induced hypothyroidism involves decreased activity of the thyroid gland caused by an adverse reaction to a medication.Causes, incidence, and risk factors Return to top
Hypothyroidism (underactivity of the thyroid gland) can cause a variety of symptoms that affect the entire body. The body's normal rate of functioning slows, causing mental and physical sluggishness. Symptoms vary from mild to severe.
Drug-induced hypothyroidism may be caused by treatment with lithium or iodides in susceptible people. Drugs used for hyperthyroidism (overactive thyroid) such as PTU and methimazole may cause unintentional hypothyroidism. Unusual causes of drug-induced hypothyroidism include nitroprusside, perchlorate, and sulfonylureas.
The most severe form of hypothyroidism is called myxedema coma, which is a medical emergency. Severe hypothyroidism, however, is seldom drug-related.
Symptoms Return to top
Early symptoms:Signs and tests Return to top
A physical examination may reveal an enlarged thyroid gland and delayed deep tendon reflexes. An assessment of vital signs (temperature, pulse, rate of breathing, blood pressure) may reveal slow heart rate, low blood pressure, and low temperature. A chest x-ray may reveal an enlarged heart.Treatment Return to top
The drug causing the hypothyroidism may be discontinued if possible. However, do not stop taking prescribed medications without first consulting your healthcare provider, as some may cause unpleasant or even life-threatening reactions if not tapered slowly or replaced appropriately.
Levothyroxine, a thyroid replacement hormone, is the most commonly used medication to treat this condition. The dose is adjusted to normalize TSH. After replacement therapy has begun, report symptoms of increased thyroid activity (hyperthyroidism) -- restlessness, rapid weight loss or sweating if they occur.
A high-fiber, low-calorie diet and moderate activity can help relieve constipation and promote weight loss if a peroid of lowered thyroid activity has lead to weight gain.
Expectations (prognosis) Return to top
With early treatment, return to the normal state is usual. However, relapses will occur if the medication is not continued. Myxedema coma can result in death.Complications Return to top
Myxedema coma, the most severe form of hypothyroidism, is rare. It can be caused by an infection, illness, exposure to cold, or certain medications. Symptoms and signs of myxedema coma include unresponsiveness to stimulation (decreased consciousness), decreased breathing, low blood pressure, low blood sugar, and below-normal body temperature.Calling your health care provider Return to top
Call your health care provider if signs of myxedema are present; or if chest pain, rapid heartbeat, or infection occur.Prevention Return to top
Medications that can cause hypothyroidism should be used with caution. Usually, the patient is monitored closely when on these medications. For example, thyroid levels may be checked periodically. Update Date: 8/6/2004 Updated by: Aniket R. Sidhaye, M.D., Division of Endocrinology and Metabolism, Johns Hopkins University School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network.
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Page last updated: 28 October 2004 |