Are Synthetic Thyroid Drugs, Like Synthroid, Actually Making Your Condition Worse?

Analysis by Dr. Joseph Mercola

synthetic thyroid drugs make conditions worse

The thyroid drug Synthroid (levothyroxine sodium), as the name implies, is anything but natural. It is not bio-equivalent to the natural hormone thyroxine, but is instead a synthetic, hormone-like substance with very different properties.

In conventional medical treatment for hypothyroidism, once blood variables fall into a range deemed "normal" thanks to the introduction of synthetic chemicals, the "treatment" is deemed a success. Unfortunately, the quality of life of the patient may actually worsen as the synthetic chemicals compete with the remaining natural hormones still being produced by their thyroid.

If you have hypothyroidism, it means you have a sluggish or underactive thyroid, which is producing less than adequate amounts of thyroid hormone. The latest estimates suggest that 20 million Americans have hypothyroidism, but the actual numbers are probably higher. Some experts claim that 10 to 40 percent of Americans have suboptimal thyroid function, which is often undiagnosed and untreated.

Unfortunately, conventional medicine's solution for hypothyroidism is virtually always the same: a prescription for Synthroid (levothyroxine), a synthetic thyroid hormone that is actually the fourth most prescribed medication in the United States.

The drug is purported to be identical to thyroxine (T4) -- the hormone that the thyroid gland naturally makes, but if you look at the structural and functional properties of each substance they are actually drastically different.

Why Synthroid is Not an Optimal Treatment for Hypothyroidism

If your thyroid gland is not producing enough T4 hormone, replacing that hormone with a man-made alternative may seem like a logical option. But there are a number of reasons why this should only be used as an absolute last resort, not a first-line treatment.

For starters, the synthetic Synthroid is not identical to your natural thyroid hormone, as far as your body is concerned.

In some cases Synthroid may actually worsen your condition, as the synthetic T4 may compete with your body's natural T4 for cellular receptor sites.

Further, conventional pharmaceutical treatment like Synthroid only replaces T4, leaving your body to convert this to T3 (triiodothyronine, the biologically active form of the hormone). Most people cannot effectively convert the T4 in synthetic thyroid preparations to T3, which may explain why research has shown that a combination of T4 and T3 is often more effective than T4 alone.

The conversion to T3 can be hampered by nutritional deficiencies such as low selenium, inadequate omega-3 fatty acids, low zinc, chemicals from the environment, or by stress.

So oftentimes taking T4 alone will result in only partial improvement.

Synthroid is also a drug that is notoriously hard to prescribe and keep within the optimal dosage range. Take too little and your hypothyroidism will not improve … take too much and you're at risk of numerous serious side effects, including bone fractures, impaired fertility, irregular heartbeat, muscle weakness, sleeplessness, vomiting and, as the Synthroid Web site notes, "other unusual medical events."

If supplementation is necessary, a better approach is combined T4 and T3 therapy. Natural thyroid products, like Armour thyroid are a combination of T4, T3 and T2 made from desiccated, or dried, porcine thyroid. Armour thyroid has gotten a bad rap over the years, perceived by physicians to be unstable and unreliable in terms of dosage. However, many improvements have been made in the product, making it a safe and effective option for treating hypothyroidism.

In fact, one study clearly demonstrated that patients with hypothyroidism showed greater improvements in mood and brain function if they received treatment with Armour thyroid than if they received Synthroid.

But perhaps the greatest issue of all is that in many cases early intervention with lifestyle changes can successfully restore your thyroid function by treating the underlying causes of the condition. It is always best to get your thyroid working again by treating the underlying cause, as opposed to taking an external source of thyroid hormone -- especially a synthetic version.

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Synthroid Does Not Address the Underlying Causes of Thyroid Problems

Taking a thyroid hormone should be done only after you have ruled out other conditions that could be causing the thyroid dysfunction such as adrenal fatigue, gluten or other food allergies, hormonal imbalance, and more.

Your thyroid is a small gland that produces two primary thyroid hormones: T4 and T3. About 90 percent of the hormone produced by the gland is in the form of T4, the inactive form. Your liver converts this T4 into T3, the active form, with the help of an enzyme. Your thyroid also produces T2, yet another hormone, which currently is the least understood component of thyroid function and the subject of much ongoing study.

Thyroid hormones work in a feedback loop with your brain -- particularly your pituitary and hypothalamus -- in regulating the release of thyroid hormone. Your hypothalamus makes TRH (thyroid-releasing hormone), and your pituitary makes TSH (thyroid-stimulating hormone). If everything is working properly, you will make what you need and you'll have the proper amounts of T3 and T4.

Those two hormones -- T3 and T4 -- are what control the metabolism of every cell in your body. But their delicate balance can be disrupted by nutritional imbalances, toxins, allergens, infections and stress. If your T3 is inadequate, either by insufficient production or not converting properly from T4, your whole system suffers.

3 Primary Factors Leading to Underactive Thyroid

From the foods you eat to chemicals in the environment, your thyroid is vulnerable to a variety of external factors. Some of the most important include:

1. Your Diet — Your diet is incredibly important for optimal thyroid function. If you follow my nutrition plan your metabolism will be more efficient, and your thyroid will have an easier time keeping everything in check. A healthy diet will also normalize your blood sugar and lipid levels and enhance your immune system, so that your thyroid will have fewer obstacles to overcome.

Eliminating junk food, processed food, artificial sweeteners, trans fats, and anything with chemical ingredients is important, and replacing them with whole, unprocessed foods, with as many organics as possible.

Gluten — As for specific foods, gluten is among the most common causes of thyroid dysfunction because it frequently triggers autoimmune responses in many people and can be responsible for Hashimoto's thyroiditis, a common autoimmune thyroid condition that is often unrecognized.

How this works is, gluten can cause your gastrointestinal system to malfunction, so foods you eat aren't completely digested (aka Leaky Gut Syndrome[7]). These food particles can then be absorbed into your bloodstream where your body misidentifies them as antigens -- substances that shouldn't be there. Your body then produces antibodies against them. These antigens are similar to molecules in your thyroid gland. So your body accidentally attacks your thyroid. This is known as an autoimmune reaction or one in which your body actually attacks itself.

Soy — Another food that typically worsens your thyroid is unfermented soy, as it is high in isoflavones (or goitrogens), which are damaging to your thyroid gland. Thousands of studies now link soy foods to malnutrition, digestive stress, immune system weakness, cognitive decline, reproductive disorders, infertility and a host of other problems -- in addition to damaging your thyroid.

Iodine — Lastly, iodine is a key component of thyroid hormone. In fact, the names of the different forms of thyroid hormone reflect the number of iodine molecules attached -- T4 has four attached iodine molecules, and T3 has three -- showing what an important part iodine plays in thyroid biochemistry.

If you aren't getting enough iodine in your diet (and most Americans don't), no matter how healthy your thyroid gland is, it won't have the raw materials to make enough thyroid hormone.

2. Stress

Stress is one of the worst thyroid offenders, as your thyroid function is intimately tied to your adrenal function, which in turn is intimately affected by how you handle stress.

Many of us are under chronic stress, which results in increased adrenalin and cortisol levels, and elevated cortisol has a negative impact on thyroid function. Thyroid hormone levels drop during stress, while you actually need more thyroid hormones during stressful times.

When stress becomes chronic, the flood of stress chemicals (adrenalin and cortisol) produced by your adrenal glands interferes with thyroid hormones and can contribute to obesity, high blood pressure, high cholesterol, unstable blood sugar, and more. A prolonged stress response can lead to adrenal exhaustion (also known as adrenal fatigue), which is often found alongside thyroid disease.

3. Environmental Chemicals

Your thyroid hormones are very vulnerable to chemicals in the environment. For instance, chlorine, fluorine and bromine are halides like iodine, which means they compete for your iodine receptors. If you are exposed to a lot of bromine, you will not hold on to the iodine you need.

Bromine is present in many places in your everyday world -- plastics, pesticides, hot tub treatments, fire retardants, some flours and bakery goods, and even some soft drinks. I have written a special article about bromine and its influence on your thyroid gland and I encourage you to read it. Other chemicals that are particularly damaging to your thyroid include:

PFOA People with the highest 25% of PFOA concentrations (above 5.7ng/ml) were more than twice as likely to have thyroid disease than those with the lowest 50% of PFOA concentrations (below 4.0ng/ml). PFOA is found in non-stick cookware, stain-resistant clothing and carpeting, food packaging and other consumer goods.

Perchlorate An endocrine-disrupting chemical known to disrupt thyroid function and hormone production by inhibiting your thyroid gland's iodine uptake. Perchlorate is a chemical used to make rocket fuel, fireworks, flares and explosives, as well as some bleach and fertilizers. It is also widely used in the defense- and pyrotechnics industries, and is now causing widespread land and water contamination in many parts of the world.

Fluoride Fluoride, which is added to many municipal drinking water supplies in the United States, is particularly damaging to your thyroid gland. Not all water filters remove fluoride, so make sure the one you have does. It is also added to most toothpastes so please be sure and use a non-fluoride toothpaste.

Triclosan A chemical used to help reduce or prevent bacterial contamination, commonly added to antibacterial soaps and body washes, toothpastes and certain cosmetics, as well as furniture, kitchenware, clothing and toys.

How do You Know if Your Thyroid is Sluggish?

Lab testing is actually not the most useful tool for diagnosing thyroid disease, as most lab reference ranges are wrong, particularly for the TSH test. Further, many cases are subclinical, and do not show up at all in standard laboratory measurements.

Unfortunately, many if not most conventional doctors do nothing but look at lab test data when diagnosing thyroid disease, and typically ignore signs and symptoms revealed by the patient, such as dry skin or hair loss. This is why it's so important that you are working with a health care practitioner who is very knowledgeable in recognizing thyroid disease and providing natural treatment options.

In my recent interview with Dr. John Lowe, who is recognized as one of the leading experts on treating thyroid disease with natural medicine, he discusses further why conventional thyroid tests may at times be completely useless for diagnosis. For example, based on three decades worth of work in this area, and two rigorous studies, Dr. Lowe has concluded that the conventional testing used does not correlate with the far more powerful assessment of thyroid hormone in your body, which is your basal metabolic rate (a low basal body temperature (BBT), less than 97.6 degrees F averaged over a minimum of 3 days, may be a sign of hypothyroidism).

So, if the conventional lab tests are unreliable, what are the signs and symptoms to look for? There are some 60 different symptoms that are indicative of thyroid disease. Dr. Lowe's web site,, contains a full list of all the signs and symptoms. Here are a few of the most common:


Hair loss

Weight gain

Dry skin, hair, eyes and other mucous membranes

Excess muscle tension and trigger points—For muscles to completely relax, filaments must lengthen and separate, which requires energy (ATP molecules). Low thyroid hormone reduces ATP

Delayed deep tendon reflexes (slow relaxation phase of the Achilles reflex)—Thyroid hormone controls gene transcription for calcium ATPase. When you hit the Achilles tendon and your foot goes down rapidly and then raises back slowly, it's a sign of hypothyroidism or thyroid hormone resistance. This is due to lack of ATP molecules to provide the energy for the contractual filaments to separate and relax, hence you get a visibly slow relaxation phase of the Achilles reflex.

Tips for Naturally Optimizing Your Thyroid Function

Thyroid disease, if left untreated, can lead to heart disease, infertility, muscle weakness, osteoporosis and, in extreme cases, coma or death -- yet it's estimated that half of the cases in the United States remain undiagnosed. So if you present certain symptoms, there's a good possibility your thyroid function could use some improvement, even if lab tests come back normal.

Fortunately, health is based on a few fundamental principles, and although you will need to address specific aspects for any particular disease, the bulk of the therapy is the same for virtually ALL diseases:

Eating a nutritious diet (a low-sugar, low-grain, mainly raw organic diet is optimally nutritious and anti-inflammatory)


Avoid soy

Avoid all sources of fluoride, in your water and your toothpaste

Normalizing hormones

Avoiding medications (virtually all medications create further imbalances, hence the side effects and deterioration of health) and environmental toxins

Addressing stress

This "prescription" is no different in the case of thyroid disease, although I do highly recommend working with a health care practitioner who can tailor these recommendations, and add more specifics, to your unique circumstances. Additional suggestions that can be used for general support of your thyroid, as well as treating an underperforming one, include:

Eat plenty of sea vegetables such as seaweed, which are rich in minerals and iodine (hijiki, wakame, arame, dulse, nori, and kombu). (Make sure they come from non-polluted waters)

Eat Brazil nuts, which are rich in selenium

Get plenty of sunlight to optimize your vitamin D levels; if you live where sunlight is limited, you may need to use a tanning bed or vitamin D3 supplementation

Eat foods rich in vitamin A, such as dandelion greens, carrots, spinach, kale, Swiss chard, collard greens, and sweet potatoes

Make sure you are eating enough animal-based omega-3 fats, such as krill oil

Use pure, organic coconut oil in your cooking -- it's great for stir fries and sautéing many different meats and vegetables.

Filter your drinking water and your bathing water

Use an infrared sauna to help your body combat infections and detoxify from petrochemicals, metals, PCBs, pesticides and mercury

Filter your home and office air, since it is one of the ways you take in environmental pollutants