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Thyroid Medicines & Side Effects

Hypothyroidism is a medical condition that occurs when the body is not producing proper amounts of necessary hormones. Hyperthyroidism is a state of too much hormone production occurring. Each condition requires a different set of thyroid medicines that have different side effects.

  1. Hypothyroid Medicine

    • Levothyroxine is the most common form of medicine prescribed to supply the body with extra T4 hormones. These help to regulate the body's metabolism, producing energy that is missing in an underactive thyroid.

    Hypothyroid Side Effects

    • Side effects may include an allergic reaction indicated by hives, difficulty breathing and swelling. Headaches, insomnia, excessive sweating, hot flashes and irritability occasionally affect patients.

    Hyperthyroid Medicines

    • Beta-blockers like propranolol are used to reduce symptoms, but they do not regulate hormone activity. Medications such as methimazole and propylthiouracil are prescribed to block the production of hormones. Should these fail, radioactive iodine is used to permanently cease the thyroid's production of hormones. This often is the only remaining option to treat an over-active thyroid and is preferable to surgical removal.

    Hyperthyroid Side Effects

    • Since radioactive iodine essentially "turns off" the thyroid's production of hormones, the primary side effect of radioactive iodine is hypothyroidism. The thyroid will not be able to produce sufficient hormone levels, so it will be necessary to take medication for that condition, likely for life.

      Side effects of propranolol could include swelling of ankles or feet, fever, sore throat, and headaches with blistering, peeling, or skin rash, loss of appetite, dark urine, strange-colored stools, or jaundice.

    Agranulocytosis

    • Agranulocytosis is a potential side effect of both methimazole and propylthiouracil, occurring in one in 1,000 patients. This is when the number of infection-fighting white blood cells in the blood decreases, raising the possibility of infection. Rash and itching commonly occur with both medications.

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