The thyroid gland is the body’s production center for three hormones, thyroxine, or T4, triiodothyronine, or T3, and calcitonin. T4 and T3 regulate the body’s ability to utilize energy, a process called metabolism. Calcitonin helps control the levels of calcium in the blood. When the thyroid gland dysfunctions, production of these hormones can be impaired. Thyroid medication is often used to either make up for decreased hormone production, or to suppress excess hormone production.
Heart Palpitations
Medication used to treat hypothyroidism, a decreased level of thyroid hormones, can cause side effects that resemble the symptoms of hyperthyroidism, or increased thyroid hormone levels. Hyperthyroidism increases the heart rate, and, as HealthLinkBC explains, those taking prescription thyroid medication for hypothyroidism may experience heart palpitations as a side effect.
Decreased Immune Function
Antithyroid medications are used to treat hyperthyroidism by causing the thyroid to produce smaller amounts of hormone. One of the side effects, according to the University of Michigan, is decreased white blood cell count. White blood cells are essential in fighting infection. A drop in white blood cell count can make it difficult for the body to fight sickness. Flu-like symptoms, such as fever, chills and throat irritation can occur when antithyroid medications are used.
Osteoporosis
Just as hyperthyroidism can increase the risk of osteoporosis, long-term use of synthetic thyroid hormone replacements can lead to bone loss, according to Drugs.com. Thyroid hormones increase the rates of metabolism, and increased metabolic demands deplete the bones by robbing them of calcium, according to the New York Thyroid Center.
Weight Changes
The increased rates of metabolism that result from increased thyroid hormone levels can cause weight loss, even in the absence or dieting or exercise. The same result can be found when synthetic thyroid hormones are taken as a treatment for hypothyroidism. Drugs.com notes that appetite changes due to medication use can also contribute to weight loss.
Hepatitis
Hepatitis is an inflammation of the liver that can sometimes occur as a side effect of antithyroid medication, according to the University of Michigan. When the liver fails to function properly, a substance called bilirubin builds up in the body. Bilirubin is formed by the waste products left over from red blood cells that have died. Often the first noticeable sign of hepatitis is yellowing of the skin or eyes due to inadequate rates of bilirubin excretion by the liver.
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