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Converting Armour Thyroid and Levothyroxine

Changing Doses of T4 and T3 Medications for Hypothyroidism

Sep 9, 2009 Melissa Murfin

Hypothyroid patients may want to try other options for thyroid treatment. Here's a quick way to convert between the various thyroid medications.

Patients with hypothyroidism have only a few options for treatment. With the current backorder of natural desiccated thyroid hormone products like Armour Thyroid, WesThroid and Nature-Throid , the options have dwindled.

Most hypothyroid patients can be treated with T4, known as levothyroxine (Synthroid, Levoxyl), alone. In some cases, symptoms of hypothyroidism are not completely relieved despite normal lab values. These people may notice some improvement when another thyroid hormone, T3, is added.

Patients experiencing these thyroid problems despite adequate T4 treatment may have been changed to natural thyroid hormones such as Armour Thyroid which include both T4 and T3. Now that availability of natural products for thyroid is a problem, some patients are switching back. This requires a dosage conversion since desiccated thyroid medications are dosed differently than levothyroxine.

Converting from Levothyroxine to Armour Thyroid and Back Again

Converting from Levothyroxine to Armour Thyroid and back again is dosed according to the old apothecary system of grains. One grain is roughly equivalent to 60 mg. According to the dose conversion table for Armour Thyroid, 60 mg of Armour is approximately equal to 0.1 mg (100 mcg) of levothyroxine.

Armour Thyroid

For example, a patient who had been on 150 mcg daily of levothyroxine might have been changed to 90 mg (1.5 grains) daily of Armour Thyroid. Now his dose of Armour has changed to 120 mg (2 grains) daily. Converting the patient back to levothyroxine from the current dose of 2 grains of Armour daily would equal levothyroxine 200 mcg daily.

Converting from Armour Thyroid to WesThroid or Nature-Throid

WesThroid and Nature-Throid are also desiccated thyroid products similar to Armour Thyroid. Converting between these medications is much simple. According to RLC Labs, these medications may all be converted on a grain-per-grain basis. One grain of Armour Thyroid is equivalent to one grain of WesThroid or Nature-Throid.

Converting to Liothyronine (Cytomel)

Liothyronine is synthetic T3 and can be added to levothyroxine for hypothyroid treatment. It is an alternative to the natural products that contain T4 and T3 in a fixed ratio. One benefit is that the individual thyroid hormones may then be adjusted separately.

Liothyronine is four times more potent than levothyroxine. Levothyroxine 100 mcg daily would be equal to 25 mcg of liothyronine. This is approximately equivalent to one grain of the desiccated thyroid medications.

To add liothyronine to levothyroxine, the dose of levothyroxine may need to be lowered first. Someone taking levothyroxine 100 mcg daily might be changed to levothyroxine 75 mcg with liothyronine 5 mcg daily. This would be roughly the same as 95 mcg of levothyroxine, not exactly the same dose but a close approximation.

What to Do

Desiccated thyroid products may be unavailable for an undefined length of time. Patients affected by the backorder situation or who want to try T3 should contact their prescribers to see what changes can be made.

The copyright of the article Converting Armour Thyroid and Levothyroxine in General Medicine is owned by Melissa Murfin. Permission to republish Converting Armour Thyroid and Levothyroxine in print or online must be granted by the author in writing.