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If you’re taking levothyroxine treatment for your hypothyroidism, but still struggling with continuing symptoms, should you consider a switch to natural desiccated thyroid (NDT)? Ahead, a look at some new research on NDT drugs, and how they may be a solution to unresolved and debilitating hypothyroidism symptoms.

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You may be one of the nearly 80% of hypothyroid patients on levothyroxine “monotherapy,” meaning you’re being treated with a synthetic version of the thyroid hormone thyroxine (T4). The remaining 20% of treated patients are taking combination therapy with levothyroxine plus liothyronine, a synthetic form of the active thyroid hormone triiodothyronine (T3), or with natural desiccated thyroid (NDT). 

According to studies, around 15% of people with an underactive thyroid continue to have persistent symptoms of hypothyroidism despite following the standard of care for the condition recommended by the American Thyroid Association. These patients are treated with levothyroxine and have blood levels of thyroid stimulating hormone (TSH) in the reference range – also known as the “normal range.” Still, these patients continue to experience nagging symptoms of hypothyroidism, such as depression, sluggishness, difficulty losing weight, and brain fog.

Some dissatisfied thyroid patients have turned to NDT drugs as an option for thyroid hormone replacement. In fact, in June of 2023, Medscape reported that the number of prescriptions for NDT medications nearly doubled between 2010 and 2020.

NDT – also referred to as desiccated thyroid extract (DTE) or “porcine thyroid” – is a thyroid drug derived from the dried thyroid gland of pigs. It contains natural forms of both the T4 and T3 hormones. NDT is a thyroid hormone replacement therapy that was the first treatment for hypothyroidism. NDT has been in continuous use since the early 1900s and remained the only drug to treat hypothyroidism for more than half of the 20^th century. Prescriptions for NDT drugs dropped significantly after levothyroxine was introduced in the 1950s. Still, several million prescriptions for NDT drugs like Armour Thyroid and NP Thyroid are still written every year, and some dedicated NDT users report that NDT is far more effective than levothyroxine at relieving their symptoms. However, the use of NDT remains controversial as the drug is often considered outdated or inconsistent by mainstream endocrinologists.

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Recently, results were released from the ARCH study, a “phase 2, multicenter, double-blind, randomized, dose-conversion study” that explored the methodology, safety, and efficacy of switching levothyroxine patients to natural desiccated thyroid (NDT). (Note: The NDT drug used in the study was Armour Thyroid.)

In one ARCH study investigation, presented as Poster 125 at the 2022 Annual Meeting of the American Thyroid Association (ATA), researchers looked at a group of hypothyroid patients with TSH levels in the reference range who were being treated with levothyroxine for at least 12 months. These patients were randomized, with one group continuing on their prescribed dose of levothyroxine, and the other group received a dose of Armour Thyroid brand NDT, with the dose calculated using a conversion chart.

During a period of 18 to 36 weeks, the study participants were titrated, and their dosage of NDT was changed as needed. After the titration period, there was a 12-week stabilization period when the dosage remained fixed.

The researchers found that 94% of the NDT participants achieved an in-range TSH by the end of the titration period compared with 97% of the levothyroxine group. The researchers concluded that NDT was safe and well tolerated.

Another investigation was undertaken as part of the ARCH study, discussed in Poster Presentation 211 at the ATA 2022 annual meeting. Researchers studied hypothyroidism patients taking levothyroxine who had persistent hypothyroid symptoms. All the patients studied had a TSH level within the study’s reference range of 0.45–4.12mIU/L at screening and had been taking levothyroxine for at least 12 months before starting the study. They also had low total T3 levels, defined as less than 87 ng/dL. The reference range for total T3 can vary slightly among different laboratories but generally falls between 71-220 ng/dL in adults.

Before switching to Armour Thyroid, researchers assessed the patients using ThyPRO, a questionnaire that evaluates the impact of thyroid disease on quality of life. It’s a self-administered questionnaire with 84 items within 13 categories. The questions relate to the physical symptoms of goiter, hyperthyroidism, hypothyroidism, eye symptoms, and the psychological symptoms of anxiety and depression. Higher scores indicate more negative symptoms and worse thyroid-related quality of life. ThyPRO also assigns an overall quality of life rating based on the results. After the study period, participants retook the ThyPRO questionnaire. The researchers found that the patients experienced a statistically significant improvement in their symptoms after the switch to natural desiccated thyroid. The researchers concluded that hypothyroid patients with persistent symptoms might benefit from switching to treatment with a natural desiccated thyroid drug.

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If you’re taking levothyroxine and experiencing persistent symptoms despite so-called “normal” levels, remember that “Normal does not mean optimal!” 

Switching to an NDT drug is undoubtedly an option to consider.  You may want to change to NDT because you prefer a more “natural” medication or because you had better symptom relief when taking NDT in the past. 

Or, you have discovered through trial and error that synthetic T4-only or combination T4/T3 therapy leaves you with continuing symptoms, despite optimizing your treatment and thyroid levels.

You can also consider other steps that could help resolve your persistent symptoms, including the following: 

• Changing to a different dosage of levothyroxine to improve your thyroid levels
• Changing brands of levothyroxine to avoid fillers and dyes that may be affecting you
• Switching to the liquid form of levothyroxine (Tirosint), which is hypoallergenic and better absorbed than levothyroxine tablets, especially for people with gastrointestinal issues or malabsorption problems
• Adding synthetic T3 to your T4 levothyroxine treatment

Keep in mind that if you do want to switch to an NDT drug, your health insurance may not cover the cost. In addition, recent regulatory developments from the U.S. Food and Drug Administration may impact the availability of desiccated thyroid treatment in the future. (You can learn more about the FDA’s regulatory actions regarding NDT in What’s Happening With Natural Desiccated Thyroid Drugs?)

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As a thyroid patient, there’s no way to know in advance which thyroid medication will safely work best for you. Ultimately, the best thyroid hormone replacement regimen for you is the medication, brand, and dosage that best and safely manages your hypothyroidism and relieves your symptoms. The right prescription usually is determined only after a trial and error period. But it’s important to know that you have options beyond levothyroxine and that despite the “bad rep” among some in the thyroid world, NDT drugs can be a safe, effective alternative for some patients. Worth a read: Levothyroxine Vs. Natural Desiccated Thyroid: What Is Right For You?

The good news is that Paloma’s team of knowledgeable thyroid doctors has an in-depth understanding of all the options for thyroid hormone replacement and will work with you to discover the best treatment for you.

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What is natural desiccated thyroid (NDT)?

NDT, also called desiccated thyroid extract or "porcine thyroid," is a thyroid hormone replacement drug made from the dried thyroid gland of pigs. It contains natural forms of both T4 and T3 and has been used since the early 1900s.

Why do some people switch from levothyroxine to NDT?

Around 15% of people treated with levothyroxine continue to have symptoms like depression, sluggishness, and brain fog even when their TSH is in the normal range. Some of these patients turn to NDT hoping for better symptom relief, and prescriptions for NDT medications nearly doubled between 2010 and 2020.

What did the ARCH study find about switching to NDT?

The ARCH study found that patients with persistent hypothyroid symptoms and low T3 levels who switched from levothyroxine to Armour Thyroid, an NDT drug, had a statistically significant improvement in their symptoms after the switch, based on a standardized quality of life questionnaire.

Is NDT as safe as levothyroxine?

In the ARCH study, 94% of patients on NDT achieved an in-range TSH by the end of the titration period, compared with 97% on levothyroxine, and researchers concluded that NDT was safe and well tolerated.

What other options are there if levothyroxine isn't relieving my symptoms?

Besides switching to NDT, options include changing your levothyroxine dose, switching brands to avoid fillers and dyes, trying the liquid form (Tirosint), or adding synthetic T3 to your T4 treatment. Your thyroid doctor can help determine which approach fits your situation.