Hypothyroidism is one of the most common and mismanaged conditions in modern medicine.
While millions are diagnosed, many more suffer from subclinical hypothyroidism, a state where thyroid function is low, but lab results still fall within the so-called “normal” range. These patients experience chronic symptoms, yet never receive proper treatment because their thyroid levels are not low enough to trigger an official diagnosis.
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, increasing ATP production and regulating body temperature, heart rate, and energy levels. 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.
Supplementing with a combination of T3 and T4 may be more physiologically supportive, ensuring 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
- 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 T4 & T3 Thyroid Therapy:
- NP Thyroid. Requires a Prescription
NP Thyroid is a prescription medication made from desiccated pig thyroid that contains both T4 and T3. Many patients find that it improves energy, metabolism, and thyroid function more effectively than T4 alone.
- Armour Thyroid. Requires a Prescription
Armour Thyroid is a prescription medication made from desiccated pig thyroid that contains both T4 and T3. Many patients find that it improves energy, metabolism, and thyroid function more effectively than T4 alone. Armour contains a few more filler ingredients compared to NP.
- Natural Dessicated Thyroid (NDT). OTC Option
NDT is an alternative to prescription options. It is often less processed and may have fewer fillers or additives compared to Armour, which is standardized for pharmaceutical use. Some prefer OTC NDT because they can adjust their dosage more freely, while others like Armour for more consistent doses.
I believe the most effective way to support thyroid health is to work with the body’s natural physiology rather than trying to manipulate it indirectly. That’s why I prefer T4 & T3 supplementation, over using herbs, seeds, or other compounds to fix thyroid function in roundabout ways.
Thyroid hormone isn’t just important, it’s essential. It runs metabolism, sustains energy, and even plays a role in cancer prevention. If levels are low, whether due to poor conversion, nutrient deficiencies, or chronic stress, providing direct support can be the difference between struggling through symptoms and actually thriving. Instead of forcing the body to compensate for what it’s missing, I believe in giving it directly what it needs to function optimally.
That being said, it’s just as important to address why thyroid conversion isn’t happening efficiently. Supporting the liver is key, since most T4-to-T3 conversion happens there. Reducing toxic burden, things like heavy metals, plastics, and endocrine disruptors, can help free up the body’s ability to regulate hormones properly. Eating small, frequent meals keeps blood sugar stable and prevents stress hormones from interfering with thyroid function. Stopping fasting is also important, since studies show fasting lowers thyroid levels and shifts metabolism into a stress state. Removing PUFAs (polyunsaturated fats) from the diet allows thyroid hormones to properly bind to cells and do their job. All of these things matter, and when they’re addressed alongside proper supplementation, the results can be much more effective than simply taking T4 medication.
For more information on thyroid health, Dr. Broda Barnes’ book, Hypothyroidism: The Unsuspected Illness, is a great resource.