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Why Standard Thyroid Therapy Usually Falls Short, the FDA's Ban on NDT, Some Recent Updates and More!
Leigh Erin Connealy
September 07, 2025
I wanted to find a way to create a deeper connection with my followers and provide more insights into the content I share on other platforms. I'm excited to give you all a closer, more personal look into my world—sharing insights from my life, my research, and work.
Why standard thyroid therapy usually falls short: 🦋
After practicing medicine for 30+ years, I’ve found hypothyroidism to be one of the most consistently overlooked drivers of disease. Unfortunately, it is one of the most common and mismanaged conditions in modern medicine.
Many people are hypothyroid and have no idea because modern medicine relies on lab values rather than recognizing clear clinical symptoms of a slowed metabolism.
If you do receive a diagnosis, the standard treatment is almost always T4-only medication like levothyroxine (Synthroid or Levoxyl).
T4 (thyroxine) is essentially a storage hormone because, on its own, it has little direct metabolic activity. It must be converted into T3 (triiodothyronine), the active form of thyroid hormone, in order to have a real physiological effect.
T4 is produced in large amounts by the thyroid gland (about 90-95% of thyroid hormone output). T3 is about 3-4 times more potent than T4. It increases ATP (energy) production, regulates body temperature, heart rate, hormone production, and countless other functions. I always say that the thyroid is like the battery to the body.
The body stores large amounts of T4 in circulation, slowly converting it into T3 as needed through deiodinase enzymes, which remove an iodine molecule from T4 to activate it.
If T4 conversion is impaired (due to stress, poor liver function, nutrient deficiencies, or high cortisol), T3 levels drop and metabolism slows, leading to symptoms of hypothyroidism, even if T4 levels appear normal in blood tests.
Excess T4 can also be converted into reverse T3 (rT3), which is biologically inactive and blocks T3 from doing its job.
Many factors disrupt the conversion process, leaving people in a state of functional hypothyroidism despite taking medication or having normal labs. Some of the biggest blockers of T4-to-T3 conversion include:
PUFAs (polyunsaturated fatty acids, like those in seed oils). Suppress thyroid function, damage receptors, and interfere with proper hormone signaling.
Poor liver function. The liver is responsible for up to 80% of T4-to-T3 conversion. Toxin overload, low glucose, and poor diet impair this process.
Low glucose levels. Without enough energy in the form of glucose, the liver cannot perform the conversion process.
Chronic Stress & high cortisol. Stress diverts T4 into reverse T3 (rT3), which blocks T3 from working.
Excess estrogen. Estrogen dominance increases thyroid-binding proteins, reducing free T3 available to cells.
Nutrient deficiencies. Low glucose, selenium, iodine, zinc, magnesium, and vitamin A impair enzyme function needed for conversion.
High iron / inflammation. Excess stored iron can cause oxidative stress, which damages thyroid receptors.
Toxins and heavy metals. Mercury, fluoride, and other environmental toxins interfere with deiodinase enzymes, blocking the body’s ability to convert T4 into active T3.
Electromagnetic fields (EMFs). Studies suggest EMFs can raise reactive oxygen species (ROS) levels, alter calcium signaling, and affect cellular stress pathways. Because thyroid hormone conversion is an energy-intensive process requiring healthy enzymes (like deiodinases), oxidative stress can impair those enzymes and reduce efficient conversion.
In many cases, supplementing with a combination of T3 and T4 is more physiologically supportive because it ensures that the body receives the active hormone it needs rather than relying solely on T4 conversion.
And interestingly, thyroid supplementation actually spans thousands of years. The earliest recorded use dates back to ancient China, where medical texts describe using chopped deer thyroids to treat conditions like goiter and energy depletion.
In the 1800s, Western physicians began using sheep thyroid extract to effectively manage hypothyroidism, marking one of the initial forms of hormone replacement therapy. By the early 20th century, desiccated thyroid from pigs and cows became widely used treatments.
Despite the success of desiccated thyroid extract, pharmaceutical companies saw an opportunity to create a patentable, synthetic version.
In the 1960s and 70s, T4-only medications (levothyroxine and Synthroid) became the new standard, under the assumption that the body would convert T4 into T3 as needed.
A lot of people today are wary of thyroid supplementation, but it may actually be more ancestrally aligned than we realize. For much of human history, eating the whole animal, including thyroid glandular tissue was common, providing a natural source of hormones. However, in 1988 the USDA implemented regulations prohibiting the use of livestock thyroid glands in food.
The removal means that modern diets no longer provide the same hormonal and metabolic support our ancestors may have benefited from.
If you are taking T4 medication or have normal thyroid levels, but are still experiencing symptoms, it may be a sign that you are struggling to convert T4 to T3.
Some signs of low thyroid function or low thyroid conversion:
Persistent fatigue even after a full night’s sleep
Low body temperature and intolerance to cold or heat fluctuations
Blood sugar issues
Constipation
Puffy face or water retention, especially in the morning
Slow reflexes or feeling physically sluggish
Dry, cracked skin
Dry, thinning hair
Loss of the outer third of the eyebrows
Hoarseness or a deeper voice than usual
Difficulty swallowing or a sensation of tightness in the throat
Slow wound healing or easy bruising
Joint stiffness and muscle cramps unrelated to exercise
Feeling detached or emotionally flat despite normal circumstances
Light sensitivity or trouble adjusting to bright environments
Some options for thyroid therapy:
Unfortunately, the FDA is moving to ban natural desiccated thyroid (NDT).
Natural desiccated thyroid (NDT) has been prescribed for over a century. However, unlike synthetic levothyroxine, which is FDA-approved, NDT was “grandfathered in” before modern drug approval laws took effect. For years, the FDA tolerated its use, but recently the agency has begun tightening oversight.
The FDA has not officially banned NDT yet, but it has moved closer by requiring manufacturers to meet biologic licensure standards—something that was never previously enforced. This means that companies producing NDT must now undergo the same rigorous (and expensive) approval process as new drugs. They have roughly a year to apply or comply, or risk being pulled from the market.
This change could drastically reduce patient access to NDT, a therapy that provides both T4 and T3. While levothyroxine-only treatment remains the FDA-approved standard, many patients report that they feel best on NDT, which more closely mirrors the hormones the human thyroid naturally produces.
If these changes go through, countless thyroid patients may lose access to a safe and effective treatment option that has helped them maintain quality of life when synthetic alternatives fell short. Patients can still access NDT for now, but it’s wise to prepare for possible disruptions over the next 12 months.
History reminds us that when natural thyroid sources were removed from food, we lost one way of accessing this essential hormone. Restricting NDT would represent another step away from nature—cutting off one of the last ways to access thyroid hormone in its complete form.
👉 You can take action: sign this petition to urge the FDA to keep NDT available as an alternative to mandatory levothyroxine-only treatment
The Celluverse Podcast is now out!🎙
I’m so excited to share that my daughter Alannah, our close friend Jess, and I have launched a brand-new podcast: Celluverse. 🎙✨ We are exploring a new way of thinking about health, the body, and what it truly means to heal.
We created this space to be honest and open. I wanted to share all of our unfiltered thoughts on healthcare, family, healing, and everything in between. The first two episodes are live now, and you can listen now on all platforms! I hope you check it out and let us know what you think! 🎧
Updates at Superpower
Superpower just launched their membership at $199/year! As a member you get 1 blood draw, 100+ biomarkers, test for 1,000+ conditions.
I’m excited that Superpower is addressing one of the biggest problems in health care: cost and accessibility. Most people are locked out of proactive, integrative care because it’s too expensive or too complicated. I'm so glad to be apart of a team that's building a new healthcare model. We need to prioritize prevention and longevity instead of just managing disease.🧡🧡🧡
Become a member here!
Health Longevity Secrets Podcast with Dr. Robert Lufkin
I also recently joined Dr. Robert Lufkin on the Health Longevity Secrets™ Video Podcast! We talked all about the real root causes of cancer, voltage healing, underlying infections, emotions, toxins, and more! You can listen to the episode here: 🤍
The second edition of The Cancer Revolution is here!
The updated edition is now available for purchase! In this version, I’ve reviewed every chapter, updated studies, incorporated the latest innovations in diagnostics, explored new early detection methods, and examined the most up-to-date research. Two brand-new chapters explore the critical role that voltage and frequency medicine play in healing and disease prevention, as well as the profound impact that the immune system and immunotherapies can have on cancer treatment. I’ve also included new recipes and food plans, updated recommendations on exercise and sleep, and more!
My hope is that this book empowers patients. That it helps you understand your options. And that it reminds you: you’re not powerless. There’s so much you can do to support healing and live a full, cancer-free life. ❤️
Talk soon ❤️,
Dr. C