Taking T3 or Natural Desiccated Thyroid Drugs

T3, natural desiccated thyroid, NDT, levothyroxine, Armour Thyroid
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If you are on thyroid hormone replacement drugs (i.e., generic levothyroxine, or the Synthroid, Levoxyl, or Tirosint brands) and are still not feeling well, one possibility is that you may benefit from adding T3, or switching to a thyroid medication that includes T3.


Levothyroxine is a synthetic form of the hormone thyroxine, abbreviated as T4. T4 is the storage hormone and must be converted by the body into T3 to be used by cells.

T3 is short for triiodothyronine. T3 is the active thyroid that works at the cellular level to help with the delivery of oxygen and energy to cells, tissues, and glands throughout the body.

While the thyroid gland produces both T4 and T3, the T4 is inactive. In order to be of use to the body, the T4 is converted to T3.

Levothyroxine-only treatment is considered the standard of care for conventional physicians. There is a growing body of scientific evidence, however, that identifies a number of issues that focus attention on T3 therapy. For example:

  • New research is identifying genetic defects known as deiodinase polymorphisms that make a subset of patients less effective at converting T4 into T3. These studies suggest that levothyroxine alone is inadequate for these patients.
  • Fifteen recent studies have evaluated levothyroxine plus liothyronine treatment for hypothyroidism. A number of the studies found improved mood, quality of life, and cognitive factors in patients taking the combination therapy, compared to levothyroxine alone.
  • Other studies have shown that using supplemental T3 results in lower cholesterol levels, a greater reduction in body weight, and better resolution of symptoms, without any additional risks when compared to levothyroxine alone.

A landmark Danish study, reported on in the prestigious European Journal of Endocrinology, studied the thyroid symptoms impact of a levothyroxine-only therapy, versus levothyroxine plus T3 (in this case, a dosage of 20 micrograms of T3 daily was used). Tests for quality of life and depression were done at the start of the study, and again after 12-week treatment periods. During each of the two 12-weeks periods, subjects were either given levothyroxine plus T3, or levothyroxine plus a placebo and then switched for the next 12-week period. Participants were "blind" in that they were not aware whether they were taking active T3 or placebo.

The quality of life and psychological factors evaluated included, among other factors: general health, social functioning, mental health, vitality, sensitivity, depression, and anxiety. The study showed that among the patients, most of whom were women, 49% of the patients preferred the combination treatment, and only 15% preferred levothyroxine-only treatment.

Researchers and endocrinologists have been going back and forth for almost two decades about the value of T3. Based on their own practical experience with patients, and on the growing body of research evidence, some conventional doctors, and more holistic and integrative practitioners are increasingly adding supplemental T3 as a solution to help optimize thyroid treatment for some patients. They add T3 in several ways:

  • Adding T3 to levothyroxine treatment, via the addition of the prescription synthetic T3 brand name drug Cytomel, or the generic liothyronine (synthetic T3)
  • Adding synthetic T3 via prescription compounded time-released /sustained-release T3 in addition to levothyroxine
  • Adding a dosage of a natural desiccated thyroid, such as the prescription drugs Nature-throid, Armour Thyroid, or generic natural thyroid (the U.S. manufacturer is Acella) to a levothyroxine treatment
  • Switching patients to a natural desiccated thyroid-only treatment approach
  • Putting a patient on a T3 only therapy (this is fairly uncommon.)

It's important to note, however, that because T3 is the active hormone, it can have an over-stimulatory effect on heart rate and pulse in some people, especially those with a history of heart disease, the elderly, and those with heart irregularities like mitral valve prolapse. T3-savvy physicians evaluate the safety of T3 as compared to the potential benefits on a case-by-case basis.

Even in those patients who do not have any heart or age-related issues that may make T3 problematic, some patients are simply more sensitive to the stimulating effects of T3. The heart is very sensitive to thyroid hormone in general, and for some people, even low doses of liothyronine, or the small amount of T3 in natural desiccated thyroid drugs can cause a rise in pulse or heart palpitations.

For those patients, some physicians recommend the time-released/sustained-release/slow-release forms of T3, available by prescription from compounding pharmacies.

Some integrative physicians, in fact, believe that the slow-release T3 is actually the optimal form for supplemental T3, as it more closely resembles the body's own conversion to and release of T3, and because the slow-release form is less likely to cause any side effects.

Natural Desiccated Thyroid

Some practitioners have found that a subset of their patients has had safe resolution of their symptoms while taking prescription natural desiccated thyroid, abbreviated as NDT. NDT is also known as porcine thyroid, thyroid extract, natural thyroid or even "pig thyroid." It is an FDA-regulated prescription drug, manufactured from the dried thyroid gland of pigs. The drugs in this category include Armour Thyroid, Nature-throid, and WP Thyroid in the United States, Canada's Erfa Thyroid, and a generic natural desiccated thyroid in the United States produced by Acella.

Natural desiccated thyroid has been in use for more than a century. Many integrative hormone experts believe that these drugs, which provide T4, T3, T2, T1, and other thyroid hormones and nutritional elements, more closely resemble human thyroid hormone than the synthetic drugs. They report that a substantial percentage of their patients feel better on them. Some patients find that they feel best on natural thyroid drugs, or on synthetic drugs plus some natural thyroid.

A Word From Verywell

Free T3 and reverse T3 blood tests, along with clinical signs and symptoms of hypothyroidism, may help identify whether you have normal levels of available T3, or may benefit from T3 treatment. Some integrative physicians believe that adequate thyroid replacement will result in free T3 levels in the middle to upper half of the laboratory reference range.

Keep in mind that T3 testing and the use of T4/T3 combination treatments and natural desiccated thyroid drugs are controversial issues. Many endocrinologists and conventional physicians are very resistant to the idea of testing T3 and treating with T3 drugs, despite the promising research findings. They cite concerns that excessive doses of T3 could cause heart palpitations or other side effects.

Many conventional physicians also do not view natural thyroid drugs favorably. They claim that these drugs are out of date, not "consistent," and many simply will not prescribe them.

If you want to consider supplemental T3 treatment or natural desiccated thyroid drugs, you may need to work with an integrative or holistic physician.

Also, while various over-the-counter thyroid support supplements are available, and some claim to contain "thyroid glandulars," these are not prescription thyroid medication, and are not a substitute for prescription natural thyroid drugs.

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