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Is Levothyroxine a Synthetic Drug?

Levothyroxine is one of the most common medications used to treat hypothyroidism. Hypothyroidism is a condition in which the thyroid gland does not secrete enough T3 and T4 hormones and, in turn, the pituitary gland works overtime to produce more TSH, or thyroid stimulating hormone, in an attempt to balance T3 and T4.

  1. A Synthetic Hormone

    • Levothyroxine is a synthetic or man-made hormone. According to the Food and Drug Administration (FDA), levothyroxine mimics the natural hormone thyroxine (T4) exactly.

    Inactive Ingredients

    • Like any medication made in a laboratory, levothyroxine contains inactive ingredients. The FDA states that levothyroxine contains gelatin, lactose monohydrate, croscarmellose sodium and corn starch; however, color additives are not added in consideration of those who are sensitive to food-grade dyes.

    Types of Levothyroxine

    • Levothyroxine is available in two forms: tablets and powder. Tablet potency varies from 0.025 mcg to 0.3 mg. Powder forms come in 200 mcg and 500 mcg vials, and are made to be mixed with liquid for injection.

    Dosing

    • Doctors generally begin treatment of hypothyroidism with very small amounts of levothyroxine, starting between 12.5 mcg and 125 mcg daily. Doses are increased very gradually, and it can take three or more weeks to take full effect.

    Side Effects

    • Levothyroxine is generally well tolerated, as it mimics the body's own hormones. The most common side effect is overdosing, which can cause symptoms of hyperthyroidism such as rapid heartbeat, sweating, intolerance to heat, difficulty sleeping, anxiousness, weight loss and diarrhea.

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