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Armour vs. Synthroid

03/29/2010

Question:

I take 75mg of synthroid but now I am trying Armour and the Dr. has me on 30mg. Is this enough?

Answer:

Thank you for contacting Net Wellness.

Synthroid® (Levothyroxine) is a synthetic version of thyroid hormone that is chemically synthesized in laboratories. Armour® Thyroid is desiccated (dried) thyroid hormone with a natural source: it is derived from the thyroid glands of pigs. Both products are used to replace human thyroid hormones in people who are not producing enough on their own.

There are two types of thyroid hormones produced in the body—T3 (triiodothyronine) and T4 (thyroxine). Synthroid® (Levothyroxine) is synthetic form of T4 by itself. Armour® Thyroid consists of a mixture of both T3 and T4 hormones. In most cases, T4 is converted to T3 adequately inside body cells. For this reason, most of the time patients respond to therapy with T4 (Synthroid®). However, this conversion of T4 to T3 can happen at different rates in different patients. For patients who may have a lower conversion rate, use of Armour® Thyroid may have benefit over Synthroid® because it supplies the T3 that a person may not be sufficiently making.

Synthroid® and Armour® Thyroid are different drugs and are thus made and dosed differently. Synthroid® is dosed in micrograms. A microgram (mcg) is one thousandth of a gram. Armour® Thyroid is dosed in milligrams (mg). A milligram is one hundredth of a gram. Synthroid® is initially dosed starting with 12.5 to 25 mcg per day. The dose is then increased by 25 mcg every 2 to 4 weeks until desired thyroid levels are reached.

A general rule of thumb for converting from Synthroid® to Armour® Thyroid is: 100 micrograms (mcg) of T4 (Synthroid®) = 60 milligrams (mg) of Armour® Thyroid.

Using that rule, your 75 microgram (mcg) dose of Synthroid® would translate to a 45 milligram (mg) dose of Armour® Thyroid. However, your starting dose of 30 mg of Armour® thyroid is appropriate and within the dosing guidelines. Armour® Thyroid is initially dosed starting with 15 to 30 mg per day. It is then usually titrated up in 15 mg increments every 2 to 4 weeks as needed until desired thyroid levels are reached.

Keep in mind that thyroid dosing is highly patient specific. The number of times your dose is increased and your final daily maintenance dose will depend on your individual response to the drug—including your measured thyroid levels and how you feel on the medication. Only a medical doctor or licensed prescriber familiar with your laboratory test results and medical history is qualified to determine the dose of Armour® Thyroid that is best for you.

Submitted by Renae Linder, PharmD Candidate
The Ohio State University College of Pharmacy

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