Wednesday, January 9th 2019 By: Dr. Jeffrey Dach, MD

Millions take synthetic thyroid hormones without realizing a natural, more bioidentical alternative exists.

As regular readers of my work will know, one of the errors in mainstream endocrinology is the dogmatic insistence on T4 mono-therapy only. Only one single medicine, T4 only, may be prescribed to the hypothyroid patient. This is the (generic) Levothyroxine or (brand name) Synthroid, which is the most prescribed drugs in America with123 million prescriptions in 2016.(1) About 7% of the population is hypothyroid and needs treatment. In my opinion, (NDT) natural desiccated thyroid is preferable to T4 monotherapy. As we will see below, NDT is more robust, more effective and safer than T4 only monotherapy with Levothyroxine. Above left image shows chemical structure of T3 and T4. Courtesy of

The Wheels of Change are Turning

The wheels of change are turning, as illustrated by Angela M. Leung, MD writing on the “Love-Hate Relationship with T4. (1) This caught my attention because it represents the beginning of a paradigm shift in mainstream endocrinology.

Subset of Patients are Dissatisfied with T4-Montherapy

With refreshing honesty, Angela M. Leung, MD points out that a subset of patients are dissatisfied with T4 only Monotherapy, and are actively seeking combination T3 and T4 treatment. Reasons cited are

1) persistent hypothyroid symptoms even though the TSH is in the “normal range” and
2) the possibility of a genetic mutation in the patient called a De-iodinase polymorphism which impairs conversion of T4 to T3 . (1)

Synthetic T3 T4 Combinations

For the “Synthetic Combination” of T3 and T4, Dr. Angela Leung will prescribe both Cytomel (T3) and Levothyroxine (T4) in dosage that replicates the T3:T4 secretion ratio of the human thyroid:

To best replicate the physiologic ratio of T3:T4 production, the separate prescriptions should be about 1:13-1:20 that of T3 to T4.[20]…A typical formula for a patient on 112 µg of synthetic T4 once daily, the new prescription is 5 µg of synthetic T3 twice daily and 100 µg of synthetic T4 daily.” (1)

Some Patients Prefer (NDT) Natural Desiccated Thyroid

In another burst of refreshing honesty, Dr. Angela Leung actually admits that some patients prefer NDT, which dates back to 1891, and was “grandfathered” in 1938 when the FDA was created. Since it was “grandfathered-in”, NDT skipped formal new- drug approval by the FDA. (1)

Left Image Figure 1 Show activity of De-Iodinase Enzyme varies according to anatomic location, Courtesy of Gereben B, McAninch EA et al 2015) (4)

Concern About 4:1 T4:T3 Ratio

NDT which contains T4 and T3 in a 4:1 ratio can be regarded as another combination therapy. Although Dr. Leung will reluctantly prescribe NDT, she will first try to dissuade the patient by disclosing drawbacks. Namely, Dr. Leung will argue NDT is suboptimal because the T4:T3 ratio in NDT is 4:1, while the thyroid secretion ratio ranges from 12:1 to 20:1. Opposing views in support of the 4:1 ratio can be found among prescribers of natural thyroid. Although the thyroid gland T4:T3 secretion ratio is 12:1, only about 20% of serum T3 comes from thyroid secretion, the other 80% comes from peripheral conversion of T4 to T3. This means the final serum levels are closer to the 3:1 or 4:1 range of which is found in NDT. Even though NDT does not replicate thyroid secretion ratio of 12:1, it does replicate the serum ratio of T4 to T3 (3:1 or 4:1), which in my opinion is more important.

Do the Calculation from Your Own Lab Sheet

Average normal Free T3 is 300 pcg/dl
Average normal Free T4 is 1.0 ng/dl= 1000pcg/dl
FreeT4/Free T3 = 1000/300 = 3.3

The serum Free T4:T3 ratio in the average patient is 3.3:1 a value closer to the 4:1 found in NDT. Remember, after the thyroid pill is ingested and absorbed, it goes into the circulating blood stream as Free T3 and Free T4. So, matching the serum T4:T3 ratio is the most logical dosing strategy.

127 Years of Use

In 15 years of clinical practice prescribing NDT to patients and family members the 4:1 ratio in NDT has NEVER been a significant issue, so I would say this is an example of a medical myth, the creation of an “imaginary” objection. Another thing to think about is this: If there were any significant problems with natural desiccated thyroid requiring a black box warning or removal from the marketplace, it would have happened by now. Natural Desiccated thyroid has been in use for over 127 years, representing the SOLE thyroid medication available from 1891 until 1955 (64 years), after which Synthroid entered the marketplace. For any drug, 127 years of use is a very long track record attesting to safety and efficacy.

Reading the Comment Section

To give you an idea of the typical results we see every week prescribing NDT, read one of the comments by CM below Dr. Angela Leung’s article on Medscape:

From: CM, Health Business/Administration
“For over 15 years of treatment for hypothyroidism with various T4 medications, I complained about continuation of hypothyroid symptoms, only to be told that my blood work was just fine. I finally found a doctor that was open to treating with desiccated thyroid medication and it completely changed my life. All of my symptoms have resolved. If patients speak, please listen and be opened minded enough to try a different medication instead of treating the lab values and not the patient. There are many people that have and would benefit from desiccated thyroid.” Comment section for (1)

Notice in the above comment, there is no mention of a problem with the NDT T4:T3 ratio which is 4:1. Left Image Shows Deiodinase activity varies in different cells…Courtesy of Figure 2 from Gereben B, McAninch EA et al 2015) (4)

My First Thyroid Patient

My first thyroid patient 15 years ago was a 70 year old female who had been on Synthroid for 50 years ever since her total thyroidectomy for a “benign cyst” at age 20. An operation, which in retrospect was probably unnecessary. Three weeks after switching her to NDT natural desiccated thyroid, she came back into the office, threw up her hands and said: “I feel so much better. Why hasn’t any other doctor done this for me before?“, I said, “I don’t know, Mom.” My very first thyroid patient was my mother. Over the years, I have found this type of patient result is typical when switching from T4 mono-therapy to natural desiccated thyroid.


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