Bioidentical Hormones 101 
The Book, by Jeffrey Dach MD

Chapter 3. Why Natural Thyroid is Better than Synthetic

Natural Thyroid Jefffrey Dach MDChapter Three.

Why Natural Thyroid

is Better than Synthetic

We use exclusively natural thyroid pills in our office, and a few times every day, I find myself explaining why natural thyroid is superior to Synthroid.  In this article, we will explain why natural thyroid tablets are better than synthetic T4 only tablets, also called Synthroid.

Left Image : Thyroxine Pill contains T4-only, courtesy of the National Institute of Health and wikimedia commons.

How Does Synthroid Differ From Natural Thyroid?

Synthroid contains Thyroxine also called T4, which is the same hormone produced by the thyroid gland.  Levothyroxine is a generic form of Synthroid.  Strictly speaking, Synthroid is bio-identical, even though it is synthetic.  Natural Thyroid pills are made from desiccated porcine (pig) thyroid glands which contain Thyroxine (T4), T3, T2, T1 and Calcitonin. 

Economics of Thyroid Pills and Synthroid

As of 2005, 10 million people in the U.S. take thyroxine. When one considers that Abbott’s Synthroid is the most popular form of thyroxine, and the second-most prescribed drug in the U.S., one starts to understand the financial rivalry between Synthroid and natural thyroid competitors.(4)

What Does Mainstream Medicine Say?

Here is a typical response to a question from a reader on a popular medical information web site called   The reader’s question is: “Dear Doctor, what is your feeling regarding natural vs. synthetic replacement therapy in hypothyroid situations? Say for example, Armour vs. Synthroid? 

The Mainstream Doctor's Answer from :


“While it is reasonable to assume that synthetic medications are less desirable than natural counterparts, in this case- natural thyroid hormone replacement is definitely not an ideal solution for the vast majority of people.


Here's why: Armour thyroid is derived from desiccated pig (porcine) thyroid gland. A number of years ago, these natural preparations were our only alternative.  Replacement with desiccated thyroid creates dosing problems because there is no way to standardize the exact amount of the dose for each batch. As a matter of fact, these preparations do not report their dosage strength in milligrams, but rather, in grains of thyroid. This is because; they don't really know the milligram equivalent in each dose.  Dosing is also based on the assumptions that each gland has equal amounts of hormones as the next gland, and that the ratio of T4 and T3 (the more active hormone) are similar and constant in each gland from the pigs. There is no way to be certain of this, and patients on these preparations often have fluctuating hormone levels, which may or may not result in symptoms.


Regardless of symptoms, the goal of replacement therapy is to keep the hormone levels as stable as possible. This is much easier to achieve with synthetic preparations such as Levoxyl and Synthroid. These preparations come in a vast number of standardized doses, allowing for minute adjustments in hormone dosing. There is another comment that should be made. With all the issues surrounding "mad cow disease" and other ailments, I personally am reluctant to offer animal based therapy to patients when a safe effective well studied synthetic preparation is widely available.  I hope this helps answer any questions you may have. Thank you for your question.  

From the Medical Author: The Mainstream Doctor M.D.



"Natural Thyroid is Not an Ideal Solution" ? !!!!

This nonsense really makes my blood boil and my eyes pop out of head.  Let's start by doing a little research. If the above doctor’s answer is true, we should expect to find that the FDA HAS NEVER recalled Synthroid because of problems with stability or potency, and we would expect that the FDA HAS recalled natural thyroid pills because they are unstable, and vary in potency. So let's ask the FDA about this.  What do we find?  In reality, the FDA says Synthroid is unstable and varies in potency, while natural thyroid from RLC labs HAS NEVER been recalled for instability or variation in potency.  (6)

Is Synthroid a Reliable and Stable Drug? 

No, Says the FDA.  Synthroid was marketed in 1955, but not FDA approved until July 24, 2002 because of a "history of potency failures...which indicates that Synthroid has not been reliably potent and stable."-- United States Food and Drug Administration Letter to Synthroid Manufacturer, Knoll Pharmaceuticals, April 26, 2001. (1)

Unstable, not of Consistent Potency from Lot to Lot

FDA document dated August 14, 1997, Docket No. 97N-0314:

"The drug substance levothyroxine sodium (also called Synthroid) is unstable in the presence of light, temperature, air, and humidity. Unless the manufacturing  process can be carefully and consistently controlled, orally administered levothyroxine sodium products may not be fully potent through the labeled expiration date, or be of consistent potency from lot to lot.  There is evidence from recalls, adverse drug experience reports, and inspection reports that even when a physician consistently prescribes the same brand of orally administered levothyroxine sodium, patients may receive products of variable potency at a given dose. Such variations in product potency present actual safety and effectiveness concerns.  However, no currently marketed orally administered levothyroxine sodium product has been shown to demonstrate consistent potency and stability and, thus, no currently marketed orally administered levothyroxine sodium product is generally recognized as safe and effective. " end quote from the FDA.  FDA Document [Federal Register: August 14, 1997 (Volume 62, Number 157)][Notices][Page 43535-43538]

Armour Thyroid Pill Recall 2005

To be completely fair, there was a recall of Armour thyroid in 2005.  Lots manufactured in 2003 were found to have lost potency 2 years later in 2005, so Forest Labs recalled all tablets made in 2003.  Since it was 2 years later, very little product from these lots was still in distribution, so it was actually a small recall.  (9-10)

Change in Armour Formulation

Armour changed their thyroid tablet formulation in 2009, and we have seen reports from patients who are not happy with the new formulation.  To avoid any questions, we use exclusively Naturethroid from RLC labs.  After five years of clinical experience with Naturethroid from RLC labs, I can fully endorse the product as an excellent form of thyroid medication.

Naturethroid Manufacturer Speaks Out: Natural vs. Synthetic

The makers of Naturethroid say this :

In contrast to Naturally Desiccated Thyroid (NDT) containing T3 and T4, most synthetic medications contain T4 (or T3) only. In reality, many patients don't start to feel normal again until they switch from synthetic to NDT (Thyroid USP). Natural Desiccated Thyroid hormone replacement has been used since the late 1800s, and it is one of the safest drugs available. It contains a full spectrum of thyroid hormones, T4 and T3 and also T2 and T1 as well.” 


“The typical indication by the proponents of synthetic T4 is that NDT is unstable and inconsistent in its dosage. However, under the full USP monograph of both Thyroid USP as an ingredient and Thyroid USP Tablet as a finished product establishing full prescription status, this conventional argument could not be further from the truth. Unlike Nature-Throid™ and Westhroid™, synthetic medications have often been recalled due to batch inconsistencies. Yet most doctors are led to believe that desiccated thyroid is unstable.


To ensure that Nature-Throid™ and Westhroid™ Thyroid USP tablets are consistently potent from tablet to tablet and lot to lot, analytical tests are performed on the raw material (Thyroid USP powder) and on the actual tablets (finished product) to measure actual T4 and T3 activity." Quoted from RLC Labs Web Site.(3)(11)



By the way, contrary to the comment above, natural thyroid tablets are labeled in milligrams.  One Grain tablets contain 65 mg of desiccated thyroid.

Conversion of T4 to T3

A common problem for many patients who don't feel well on Synthroid is the inability to convert T4 to T3 .  Synthroid contains T4 which is inactive, and must be converted to T3 by the body for it to work.  This conversion is done by a de-iodinase enzyme, which is a selenoprotein .  In patients with selenium deficiency, this enzyme is not working properly, and many of these patients have an inability to convert T4 to T3.  Selenium supplementation is useful here.  In my experience, most patients feel much better, with more energy, and relief of symptoms when switching from Synthroid to a natural thyroid such as Naturethroid.

Important Point:

Natural thyroid medication is clinically superior to T4-only thyroid such as levothyroxine and Synthroid.

Mary Shomon on Natural Thyroid vs. Synthetic

An article by Mary Shomon in the Townsend letter explains why natural thyroid treatment is better, that Synthroid and Levothyroxine are unstable, with dosage varying according to batch, and subjected to multiple recalls. (1)  Natural thyroid from RLC labs has never been recalled and is the preferred solution. Mary Shomon's blog is an excellent resource on natural thyroid.(6)(10)(12)

Can I Get Mad Cow Disease from My Pig Thyroid Pill?

Millions of Americans have enjoyed ham sandwiches and pork products for decades without a single case of Mad Cow Disease ever reported.  This essentially invalidates the fear of Mad Cow Disease as an argument.  However, Mary Shomon advises caution with over-the-counter glandular supplements, which may contain unregulated meat products from areas of Europe known to have mad cow infected livestock. (12)

Stop the Thyroid Madness

Another excellent resource is the Stop Your Thyroid Madness Blog and Book by Janie Bowthorpe.  Janie suffered for years with low thyroid symptoms even while on Synthroid, and had a dramatic recovery after converting from Synthroid to natural thyroid.  Her book makes a strong statement as an advocate for natural thyroid medication.(14)

Our Program: 

For diagnosis of a low thyroid condition, a lengthy questionnaire is used. This reviews over 70 symptoms of the low thyroid condition.  In addition, lab testing includes a complete thyroid blood panel with TSH, free T3 and free T4, Thyroid antibodies.  Physical examination includes measurement of reflex time. Also included is a basal body temperature chart filled out by the patient at home.   We also measure serum selenium and spot urinary iodine levels, and supplement when found low.  Both tests are widely available at the larger national labs.   Once it has been determined that thyroid hormone is likely to be beneficial, a trial of low dose Nature-Throid from RLC labs is started with a Half Grain (32.5 mg) tablet every other morning.

A log book is kept by the patient describing benefits of increased energy, clarity of mind, etc, or adverse effects such as palpitations, feeling of warmth, anxiety or insomnia. At the end of a week, the log book is reviewed to determine if the thyroid was of benefit.

We have found that monitoring symptoms with a log book, and the Half Grain gradual increments in thyroid dosage every two to three weeks makes this program very safe. In the event of rapid heart rate or palpitations, the patient is instructed to hold the daily dosage of thyroid medication and inform the physician. This program is also excellent for switching patients from Synthroid to Natural Thyroid with patients invariably reporting dramatic improvement afterwards.

Instead of Natural Thyroid, Why Not Use Cytomel and Synthroid Together?

Cytomel is T3 and Synthroid is T4, so why not use the two together? The Cytomel provides the missing T3 to make a combination that is closer to the Natural Thyroid.  Some patients arrive at my office having been given this combination from the doctor.  The advantage for the prescribing doctor is that both items, Synthroid and Cytomel are available at the corner drugstore, whereas natural thyroid is available from a compounding pharmacy.  Natural Thyroid is still the preferred choice. Among other missing ingredients, the Synthroid and Cytomel lacks Calcitonin which is present in natural thyroid, and usually lacking in patients after thyroidectomy which removes the parathyroid glands.  Giving back the missing Calcitonin makes sense, and patients usually feel better..

This is Part One of a Series. For Part Two Click Here.

Articles with Related Interest:

Why Natural Thyroid is Better than Synthetic Part One
Why Natural Thyroid is Better than Synthetic Part Two
Why Natural Thyroid is Better than Synthetic Part Three

References for Chapter 3. Why Natural Thyroid is Better than Synthetic

(1);col1  Treating hypothyroidism naturally, Townsend Letter for Doctors and Patients, Feb-March, 2002 by Sunny Willmington, Howard Hagglund,  and Mary Shomon - Natural vs. Synthetic Thyroid

(2) The Synthroid Settlement: Fair Payoff or Patient Ripoff? By Mary Shomon,  December 14, 2003

(3)   Westthroid- Natural vs Synthetic Thyroid

(4)  Chemical and Engineering News. The Top Pharmaceuticals That Changed The World Vol. 83, Issue 25 (6/20/05) Today, more than 10 million people in the U.S. take thyroxine. Synthroid, manufactured by Abbott Laboratories and the most popular brand of thyroxine, is the second-most prescribed drug in the U.S.

(5) Larry Frieders, the compounder, THYROID MADNESS DEFINITION:

(6)   Synthroid Has a Long History of Problems, Says FDA  In Denying Synthroid's Request for Special Approval Status, FDA's Scathing Letter Outlines History of Subpotent Product, Inconsistency and Poor Stability   by Mary Shomon

(7) Medicine net web site

(8) What's up with desiccated thyroid & the FDA?

(9)  Between 1991 and 1997, there were ten recalls of synthetic T4, involving over 100 million tablets.9 In nine of these recalls, the tablets had been found to be subpotent, or they were losing their potency before their expiration date; in the tenth recall, the tablets were found to be too potent.. Source: Federal Register 62, No. 157, 14 August 1997, pp. 43535-8.

(10)  What Forest found in recent sample testing was that there were several lots of Armour Thyroid that were not maintaining full potency.

(11)  Unlike Nature-Throid™ and Westhroid™, synthetic medications have often been recalled due to batch inconsistencies.

(12) Is There A Real Risk of Mad Cow Disease from Armour Thyroid?  An Update on Armour Thyroid and Glandulars by Mary Shomon

(13)  Desiccated Thyroid References

(14) Stop the Thyroid Madness: A Patient Revolution Against Decades of Inferior Treatment. Janie A. Bowthorpe. Grape Publishing (2008)

Website Builder