Show 1452: Why Is the FDA Planning to Ban Natural Desiccated Thyroid?

When the thyroid gland stops working efficiently, the effects resound throughout the entire body. That’s because this little gland controls metabolism in all our tissues. Before there was a treatment, thyroid disease was sometimes deadly. Doctors started prescribing natural desiccated thyroid derived from animals 130 years ago. This worked well. Synthetic levothyroxine (a thyroid hormone) was developed in 1970 and marketed aggressively. Now levothyroxine is one of the most commonly prescribed medications in the US. The FDA has announced that it plans to ban natural desiccated thyroid. What are the implications? We’ll check in with two experts to find out.

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What Should You Know about Natural Desiccated Thyroid?

Thyroid extract from pigs contains two important thyroid hormones. Endocrinologists refer to them as T4, also called levothyroxine, and T3, known as liothyronine. The T4 molecule has 4 iodine atoms and is inactive. To activate it, the body uses an enzyme, deiodinase, that kicks off one iodine molecule resulting in activated T3 that does all the work in the tissue. When scientists discovered that T4 could be converted to T3, it opened the door to prescribing T4 alone, synthetic levothyroxine such as Levoxyl or Synthroid, to all hypothyroid patients.

That became standard practice not long after Synthroid was introduced. There was a hitch, however. Some patients did not feel well even though they were taking levothyroxine. Until fairly recently, doctors downplayed these problems.

Our guest, Dr. Antonio Bianco, helped conduct the research showing that some people have deiodinase enzymes that are less efficient at converting T4 to T3 (Current Opinion in Endocrinology, Diabetes, and Obesity, Oct. 2018). This enzyme activity seems to be under genetic control. As a result, endocrinologists may find it easier to understand why some patients don’t respond to prescribed levothyroxine as expected. They may need liothyronine in addition. This could be provided with a separate prescription. On the other hand, people get both T3 and T4 when they take natural desiccated thyroid.

What Symptoms Do People Suffer Without Natural Desiccated Thyroid?

A majority of hypothyroid patients, perhaps 80 or 85 percent, are able to convert T4 to T3 well enough that they can use levothyroxine alone. The remainder, however, do not feel well on this regimen. They experience brain fog and low energy. They may also complain of other symptoms associated with undertreated hypothyroidism, such as difficulty with weight control, cold sensitivity and menstrual irregularities or fertility problems in women. An estimated 1.5 million Americans take natural desiccated thyroid. What will they do if the FDA bans this product? About half a million people take a combination of synthetic T4 and synthetic T3. That is one option, but some individuals prefer natural hormone.

What Will Happen to Patients?

We turn to patient advocate and activist Mary Shomon to learn about the patient perspective. She is concerned about the FDA’s announced plan to take natural desiccated thyroid (NDT) off the market in August 2026. (NDT is sometimes referred to as DTE, desiccated thyroid extract. They are the same thing.) It is not clear that the agency has considered what will happen to people forced to take a medicine that most of them have already tried without success, levothyroxine.

Rethinking Levothyroxine Treatment:

Mary Shomon points to recent research by Dr. Bianco and his colleagues suggesting that levothyroxine alone may not be quite as effective as most endocrinologists believe. In this analysis of medical records, hypothyroid people taking levothyroxine alone were twice as likely to die during the study period and had a 40% higher risk for developing dementia compared to people getting T3 along with T4 (Journal of Clinical Endocrinology, June 20, 2025). These new findings underscore the importance of information from the large number of patients in touch with Mary. As she says, there is enormous individual variation in which treatments help people thrive. She recommends that everyone who relies on natural desiccated thyroid should contact the FDA (as well as their Congresspeople) to let them know how banning these products would affect their lives.

This Week's Guests:

Antonio Bianco, MD, PhD, is Senior Vice President of Health Affairs, Chief Research Officer and Dean of the John Sealy School of Medicine at the University of Texas Medical Branch at Galveston. Dr. Bianco is the author of Rethinking Hypothyroidism: Why Treatment Must Change and What Patients Can Do.

[caption id="attachment_137600" align="alignnone" width="768"] Antonio Bianco, MD, PhD
VP & Vice Provost Research & CRO, Research Services[/caption]

Mary Shomon is a patient advocate and author. Her books include the New York Times bestseller The Thyroid Diet and ten others. Her website is  https://www.mary-shomon.com
She is also a Paloma Health Advisor & Patient Advocate. Find her online at https://www.palomahealth.com/authors/mary-shomon
Her newsletter, Sticking Out Our Necks Hormonal Health News, is available on Substack. Here's the link: https://hormones.substack.com/

[caption id="attachment_137601" align="alignnone" width="768"] Patient advocate Mary Shomon[/caption]

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