Armour Thyroid Vs. Levothyroxine: What Is The Difference?

In our latest question and answer, the pharmacist discusses the difference between levothyroxine and Armour Thyroid.

Armour Thyroid Vs. Levothyroxine: What Is The Difference?
Jun 06, 2018

Becky asked

What are the differences that a patient may feel between being on levothyroxine and then switching to Armour? Side effects, positive benefits, etc. Also, can you explain how the two work differently/the same?


Levothyroxine bottleThe main difference between levothyroxine and Armour Thyroid is:

  • Levothyroxine contains synthetic T4 (thyroxine).
  • Armour Thyroid is a desiccated thyroid product, which is ground-up, dried and powdered thyroid from pigs. 
  • Armour Thyroid contains both T4 (thyroxine) and T3 (triiodothyronine).

Armour Thyroid is one of the more popular desiccated thyroid products available by prescription. Others include:

  • Armour Thyroid NP
  • Thyroid WP
  • Thyroid Nature-Throid

Preferred Treatment Of Hypothyroidism

For the treatment of hypothyroidism (low thyroid levels), levothyroxine is the most commonly prescribed medication and is the recommended treatment per most medical guidelines, such as those from the American Thyroid Association.

While the T4 hormone is active, it is significantly less-so than T3 and is converted in our bodies to T3. Most individuals are successfully treated for their hypothyroidism with T4 products, such as levothyroxine. Available T4 products include:

  • Levothyroxine (generic)
  • Synthroid (brand)
  • Levoxyl (brand)
  • Tirosint (brand - hypoallergenic)

The vast majority of guidelines and studies state that desiccated thyroid products are not recommended for the treatment of hypothyroidism for most people. In fact, the American Thyroid Association guidelines state the following:

"Thus, there are no controlled trials supporting the preferred use of desiccated thyroid hormone over synthetic L-thyroxine in the treatment of hypothyroidism or any other thyroid disease."

Nevertheless, there are a large number of patients that swear they get better effects after being switched to a desiccated thyroid product such as Armour Thyroid. This may be for several reasons, some of which are described in the next section.

Why Armour Thyroid May Be Preferred Over Levothyroxine

One reason why an individual may feel they are having a better response to Armour Thyroid over levothyroxine is if their bodies cannot efficiently convert T4 to T3. For example, in those with Hashimoto's thyroiditis, an autoimmune disease that can alter how the thyroid functions, there may be a decreased ability to convert Tto T3. In these patients, taking T4 from levothyroxine may not produce acceptable results.

Other factors that can affect how our bodies convert T4 to T3 include:

  • Chemothrerapy
  • Kidney disesase
  • Liver disease
  • Diabetes
  • Slcohol
  • Stress
  • Smoking
  • Obesity
  • Hormone imbalance

Another reason why some individuals prefer Armour Thyroid over levothyroxine is because they may actually be getting too much liothyronine (T3) from the medication. Too much T3 could potentially cause hyperthyroid effects. In fact, one study reported that the ratio of T3 to T4 in desiccated thyroid products can be almost four times higher than what is normally secreted by the human thyroid.

Hyperthyroid effects, from too much T3, may feel preferable for hypothyroid patients as they may feel a boost in energy and decrease in appetite, among other effects. However, too much T3 has significant risks such as an increased risk of cardiovascular adverse effects (e.g. atrial fibrillation) and osteoporosis. It is important to have your thyroid levels consistently checked when taking any thyroid medication, but especially with desiccated thyroid products.


  • Levothyroxine contains synthetic T4, which the body then converts to the more physiologically active T3.
  • Armour Thyroid is a desiccated thyroid product that contains both natural T3 and T4.
  • Levothyroxine is the preferred treatment of hypothyroidism, but some individuals, such as those who cannot convert from T4 to T3 efficiently, may benefit from desiccated products.
  • Watch for adverse effects with desiccated thyroid products as they can sometimes result in T3 dosing that is too high.

Ready for a more personal experience with your meds?