Differences between levothyroxine and thyroxine

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Levothyroxine and thyroxine are two synthetic thyroid hormones used to treat hypothyroidism. While they both aim to supplement the body’s thyroid hormone levels, there are some key differences between the two.

Levothyroxine is the most commonly prescribed thyroid hormone replacement medication. It is a synthetic form of the thyroid hormone thyroxine (T4). Thyroxine is the natural hormone produced by the thyroid gland. Here are some of the main differences between these two medications:

Composition and structure

Levothyroxine, also known as L-thyroxine, is a synthetic form of the thyroid hormone thyroxine (T4). It is chemically identical to the thyroxine produced by the thyroid gland. Levothyroxine is commonly used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone.

Levothyroxine is available in tablet form and is usually taken orally. The drug is absorbed in the gastrointestinal tract and converted into its active form, triiodothyronine (T3), in the body. Levothyroxine works by increasing the levels of thyroid hormone in the body, which helps to regulate metabolism, growth, and energy levels.

The structure of levothyroxine consists of a tyrosine backbone with four iodine atoms attached. This structure is crucial for the hormone’s function in the body, as iodine is essential for the production of thyroid hormones.

Therapeutic uses


Levothyroxine is commonly used to treat hypothyroidism, a condition where the thyroid gland doesn’t produce enough thyroid hormone. It helps restore the hormone balance in the body and can alleviate symptoms such as fatigue, weight gain, and cold intolerance. Levothyroxine is also used to prevent the recurrence of thyroid cancer after surgery.

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Thyroxine is a hormone produced by the thyroid gland and is essential for regulating metabolism and energy levels in the body. It is used in the treatment of hypothyroidism and certain thyroid disorders. Thyroxine replacement therapy can help alleviate symptoms such as fatigue, weight gain, and depression in individuals with an underactive thyroid gland.

Side Effects


Common side effects may include hair loss, weight changes, and headaches. More serious side effects could include chest pain, rapid heartbeat, and signs of an allergic reaction like rash or swelling.

It’s important to consult with your doctor if you experience any side effects while taking levothyroxine.


Side effects of thyroxine may include nausea, sweating, and tremors. In some cases, individuals may experience palpitations, insomnia, or abdominal pain as well.

If you notice any unusual or severe side effects while using thyroxine, seek medical assistance promptly.

Interactions with other medications

Interactions with other medications

Levothyroxine may interact with other medications, affecting its absorption, metabolism, or effectiveness. It is important to inform your healthcare provider about all the medications you are taking before starting levothyroxine therapy.

Medications that may interact with levothyroxine:

Drug Class Examples
Antacids Aluminum hydroxide, calcium carbonate
Anti-seizure medications Phenytoin, carbamazepine
Antidepressants Sertraline, fluoxetine
Cholesterol-lowering drugs Cholestyramine, colestipol

These are just a few examples of medications that may interact with levothyroxine. Always consult your healthcare provider for personalized advice based on your individual medical history.

Availability and cost

Levothyroxine and thyroxine are widely available in pharmacies and can be obtained with a prescription from a healthcare provider. They are commonly prescribed medications for the treatment of hypothyroidism and other thyroid-related conditions.

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The cost of levothyroxine and thyroxine can vary depending on the brand, dosage, and insurance coverage. Generic versions of these medications are typically more affordable than brand-name options. Some insurance plans may cover the cost of these medications, while others may require a copay or out-of-pocket payment.

Patients should consult their healthcare provider or pharmacist for information on the availability and cost of levothyroxine and thyroxine in their area. It is important to adhere to the prescribed dosage and schedule to ensure the effectiveness of treatment and minimize the risk of side effects.

Regulation and prescription requirements

Regulation: Levothyroxine and thyroxine are regulated medications that are typically available by prescription only. They are classified as prescription drugs due to their potency and potential for side effects if not taken correctly. In most countries, these medications are regulated by government health agencies to ensure their safe and effective use.

Prescription Requirements: To obtain levothyroxine or thyroxine, a prescription from a healthcare provider is usually required. This is because these medications contain thyroid hormones, which can have significant effects on the body’s metabolism and overall health. Healthcare providers will typically prescribe these medications based on a patient’s specific thyroid condition and individual needs. It is important to follow the prescribed dosage and instructions for these medications to achieve the desired therapeutic effects and minimize the risk of side effects.