Over 100 years ago, doctors started making extracts from the dried, ground-up thyroid glands of pigs to treat thyroid disorders. Their popularity had waned, but we are now experiencing their modest resurgence. Uncover the unique history of Armour Thyroid and find out whether it has any advantages over modern-day medications like Synthroid.

What Is Armour Thyroid?

Armour Thyroid is the brand name for a naturally-derived medication called desiccated thyroid extract. Other brand names include NP Thyroid and Nature-Throid. All require a prescription in the US.

These extracts are made from the thyroid glands of animals, typically from pigs. Hence, they have a strong, unpleasant odor. The thyroid glands are first dried and turned into a powder (“desiccated”). They are then packaged into ready-to-use products [1].

Armour Thyroid is used to treat low thyroid hormone levels or hypothyroidism [1].

It contains two thyroid hormones, which are normally produced by the thyroid gland: thyroxine (T4) and triiodothyronine (T3) [2].

Once the standard treatment for hypothyroidism, the use of thyroid gland extracts today has fallen out of favor. These products lacked standardization and their strength varied from batch to batch, making their benefits unpredictable. Most doctors bade them farewell in the ‘60s once the pure, individual thyroid hormones become widely available [2, 3].

Many organizations do not recommend the use of thyroid extracts today due to similar concerns about the products’ safety and effectiveness [4].

However, thyroid extracts are experiencing a small resurgence. Patients who are not satisfied with conventional treatments are now seeking alternatives. Some practitioners report improved patient outcomes, compared to synthetic hormones. And although thyroid extracts are being revisited as a natural solution, clinical evidence is lacking to support their effectiveness [1].

Did you know? Armour Thyroid was developed by Armour & Company, a leader in the meatpacking industry at the time. They used the thyroid glands from their pigs to create the medication [2].

How Armour Thyroid Works

Our thyroid gland primarily produces two hormones, thyroxine (T4) and triiodothyronine (T3) [5].

T3 is the stronger of the two and is generally the one that affects our body. T3 plays a role in a variety of functions including metabolism, heart rate, and body heat [5].

Armour Thyroid is used when people cannot produce enough thyroid hormones on their own, a condition called hypothyroidism [2].

Armour Thyroid contains T3 and T4 that is extracted from pigs. These animal thyroid hormones work similarly in humans and help restore hormone levels [2].

History of Armour Thyroid

The first recorded use of desiccated thyroid extract was in 1891 [1].

After that, animal extracts quickly became the standard treatment for hypothyroidism [1].

Even after synthetic versions of T4 and T3 were invented, thyroid extracts remained the preferred choice. The extracts contain more T4 than T3, and many believed that the content in the extracts better matched the levels found in humans. Some practitioners still hold this stance [1].

However, several key discoveries changed how most doctors viewed thyroid extracts [1].

One major finding was that much of the T3 found in humans is converted from T4. Scientists also found that the thyroid gland normally secretes about 14 times more T4 than T3 [1].

These findings implied that the body primarily uses T4, which is converted to T3 when needed. Researchers reasoned that using T4 alone and letting the body decide when to convert it to T3 may be safer and more effective [1].

However, this equation might not work for everyone. A number of people have issues converting T4 to T3 (see “Advantages of Armour Thyroid” below).

Another big problem remains the inconsistent quality of thyroid extract products. Researchers found that the strength and ingredients inside could vary wildly [1].

Over time, these discoveries prompted a major shift towards the use of levothyroxine, a synthetic T4 medication [1].

Fast-forward to today, almost all guidelines on hypothyroidism do not recommend the use of thyroid extracts [4].

Armour Thyroid for Hypothyroidism

Armour Thyroid is primarily used to treat low thyroid hormone levels or hypothyroidism [1].

Desiccated thyroid extracts, like Armour Thyroid, have long been used to replenish thyroid hormones in humans, Despite this, very few studies have evaluated their effects [1].

However, studies do show that many people prefer thyroid extracts.

In an online survey of over 12k hypothyroid patients, desiccated thyroid extract users were more satisfied with their medication than people taking levothyroxine. Patients preferred thyroid extracts over synthetic combinations of T4 and T3 as well [6].

Thyroid extract users were also less likely to report problems with weight, energy levels, and mood [6].

A different study of 70 people revealed similar results: almost half of the participants preferred thyroid extracts over levothyroxine [7].

Most probably, users prefer thyroid extracts because these are derived from natural sources rather than being produced in the lab. Most people view thyroid extracts as safer natural alternatives, although evidence points to the contrary.

Bottom Line

Synthetic thyroid hormones are the mainstay treatment for hypothyroidism, and for good reason. Clinical trials confirmed they are safe and effective.

However, they might not be for everyone. Some people prefer desiccated thyroid extracts, such as Armour Thyroid. Although naturally-derived, Armour Thyroid may carry greater risks and side effects than synthetic thyroid hormones. Talk to a doctor before taking it.  

Armour Thyroid vs. Synthroid

Levothyroxine (Synthroid) is currently the standard treatment for hypothyroidism [4].

It’s also not too different from Armour Thyroid.

Levothyroxine is a man-made version of T4 that is converted to T3 by your body. In contrast, Armour Thyroid contains T4 and T3 that is extracted from pigs [1].

Naturally, the two drugs draw many comparisons. Let’s take a closer look at the advantages and disadvantages of each.

Advantages of Armour Thyroid

Improvements to Weight and Mood

Thyroid hormone replacement that includes T3 may have several unforeseen benefits.

For instance, one study of 70 people found that desiccated thyroid extracts cause more weight loss than levothyroxine. Although the weight loss was modest, only about 3 lbs, almost half of the patients said they preferred thyroid extracts [7].

This, in no way, means that weight loss goals justify thyroid extract use in people with normal thyroid function.

A different study of 33 people compared levothyroxine to combination therapy with T4 and T3. The combination was better at improving mood and cognitive performance [8].

Genetic Factors Affecting T4 Conversion

Recent research suggests that some people may have trouble converting T4 into T3, due to genetic factors [9, 10].

Specifically, a genetic variation in rs225014 may affect the enzymes responsible for thyroid hormone conversion [11].

A study found that people with this genetic variation respond better to combination therapy with T4 and T3. Patients also reported increased well-being [11].

Additionally, mutations of the MTHFR gene can affect levels of vitamin B12, which is important for thyroid function and the conversion of T4 to T3. The 677TT genotype of MTHFR (AA at rs1801133) is strongly linked to vitamin B12 deficiency [12, 13].

Nutrient Deficiencies Affecting T4 Conversion

Several nutrients play an important role in thyroid hormone conversion.

For example, the enzymes responsible for T4 conversion contain selenium [14].

A study of 109 people found that low selenium levels correlate to a low T3/T4 ratio in the elderly [14].

Zinc is also important for this conversion. Studies show zinc supplements can improve thyroid hormone levels in those with zinc deficiency [15, 16].

Many of the different B vitamins play an important role in metabolism and thyroid function. One study found that up to 40% of hypothyroid patients may also have a vitamin B12 deficiency [17].

Individuals who are unable to correct these deficiencies may benefit from therapy that includes T3.

Subclinical Hypothyroidism

Subclinical hypothyroidism is often thought of as a milder form of hypothyroidism. In this condition, people typically have elevated TSH levels, but normal T3 [18].

There is also some debate on whether subclinical hypothyroidism should be treated. Affected individuals commonly have no signs or symptoms [19, 18].

The problem is that subclinical hypothyroidism can progress into actual hypothyroidism. This condition may also be a risk factor for heart disease, especially if TSH levels are greater than 10 mIU/L [19, 18].

Studies looking at the treatment of subclinical hypothyroidism with levothyroxine have revealed mixed results [19].

On the other hand, one review of case reports found that treatment with Armour Thyroid leads to better clinical results than levothyroxine [20].

Patient Preference

Many patients seem to prefer desiccated thyroid extracts over levothyroxine or other synthetic medications.

An online survey of 12k people found that people taking thyroid extracts were more satisfied with their treatment and less likely to report issues with weight, tiredness, mood, and memory [6].

Disadvantages of Armour Thyroid

High Amounts of T3

Armour thyroid contains T4 and T3 in about a 4:1 ratio [4].

However, your thyroid glands naturally secrete T4 and T3 in a 14:1 ratio [4].

This means that Armour Thyroid delivers much more T3 than what you naturally produce, which can cause several problems [4, 2].

For example, studies have found that desiccated thyroid extracts cause spikes in T3 levels that can lead to hyperthyroid symptoms [21, 4].

On top of that, taking T3 may have minimal benefit.

An analysis of 13 clinical trials and 4 reviews concluded that combination T3 and T4 therapy is not better than levothyroxine alone [4].

Product Variability

One of the main reasons thyroid extracts fell out of favor was because product quality can be inconsistent [1].

In the past, studies found that some desiccated thyroid extract products contained no active thyroid hormone, while others had almost double the expected amount [22, 1].

Today, the consistency of these products has improved and they are standardized. However, their content is still more likely to vary compared to synthetic drugs like levothyroxine [1].

Not FDA-approved

Although thyroid extracts are regulated by the FDA, they are actually not an FDA-approved drug.

This is partly because desiccated thyroid extracts existed before the formation of the FDA, so they never went through the drug approval process [2].

Their unique status makes it difficult to perform clinical trials on Armour Thyroid, due to safety and funding issues.

As a result, studies about the safety and effectiveness of Armour Thyroid are desperately lacking.

Not Recommended in Pregnancy

Many organizations, like the American Thyroid Association and the American Association of Clinical Endocrinologists, recommend against the use of DTEs in pregnancy [4].

One major issue is that the safety of thyroid extracts has never been studied in pregnancy [4].

Another reason is that T4 is essential for the development of fetal brains. Thyroid extracts, which contain lower concentrations of T4, may negatively affect development [23, 4].

Levothyroxine, in comparison, has been shown to be safe and effective during pregnancy and breastfeeding [4].

Armour Thyroid Side Effects & Precautions

The side effects of Armour Thyroid have not been evaluated by clinical trials or the FDA.

Based on the few studies that have looked at Armour Thyroid, side effects do not appear to differ from levothyroxine treatment [6, 7].

In general, thyroid hormone medications have minimal side effects. Instead, side effects mostly arise when hormone levels fall out of the normal range [4].

Because of their high T3 concentration, DTEs may be more likely to cause thyrotoxicosis, or an excess of thyroid hormones [24, 4].

Some symptoms of high thyroid hormone levels include [25]:

  • Appetite changes
  • Difficulty sleeping
  • Tiredness
  • Sweating
  • Irritability

Is Armour Thyroid Safe?

No studies have looked at the long-term risks of taking Armour Thyroid.

Based on how it works, Armour Thyroid likely shares many safety concerns with synthetic thyroid hormones.

For instance, levothyroxine products carry a warning that they may cause bone loss. This is especially a concern in postmenopausal women [26].

Thyroid hormone replacement is also associated with cardiovascular disease. Individuals with preexisting heart disorders are usually advised to take lower doses [27].

Additionally, thyroid hormones may increase the inflammatory and immune response. This should be evaluated case by case, especially in people with autoimmune issues [28].

Pregnancy

Armour Thyroid is generally not recommended during pregnancy [4].

This is mostly due to a lack of research – no studies have looked at the safety of desiccated thyroid extracts in pregnancy [4].

Another issue is that desiccated thyroid extracts contain lower concentrations of T4 compared to levothyroxine. Research shows that adequate T4 levels are crucial for fetal brain development [23, 4].

If you are pregnant or plan to become pregnant, it’s best to discuss treatment options with your doctor.

Contraindications

Thyroid hormone medications should not be taken in certain situations, including [27, 29*]:

  • When thyroid hormones are elevated, such as in thyrotoxicosis
  • During a heart attack
  • With uncorrected adrenal insufficiency
  • If there is an allergic reaction to drug ingredients

*Based on the product label.

Drug Interactions

Thyroid hormone therapy can cause many drug interactions [30].

Some common potential interactions include [29*]:

*Based on the product label.

One recent case report describes another dangerous interaction. An adult man experienced a heart attack that was likely caused by the use of testosterone with Armour Thyroid. He was a bodybuilder who took this risky cocktail to lose weight and gain muscle [31].

This is also not a comprehensive list. Let your doctor know about all the medications and supplements you are currently taking to better look for any interactions.

Armour Thyroid Dosage & Strengths

Armour Thyroid comes in tablet form with strengths that range from 15 mg to 300 mg.

Dosage strengths are sometimes written in grain, an old unit of measurement. For Armour Thyroid products, one grain is equal to 65 mg, which is sometimes listed as 60 mg [4].

Armour thyroid contains T3 and T4 in about a 1:4 ratio.

For example, a 60 mg tablet contains about 9 mcg (micrograms) of T3 and 38 mcg of T4 [4].

A typical starting dose of Armour Thyroid for adults is a 30 mg tablet per day, but should be individualized to each person. It is adjusted by increments of 15 mg every 2 – 3 weeks, based on lab results of TSH, T3, and T4.

Maintenance doses usually range from 60 mg to 120 mg per day.

Armour Thyroid Ingredients

Aside from the crushed thyroid glands of pigs, other ingredients in Armour Thyroid are calcium stearate, dextrose, microcrystalline cellulose, sodium starch glycolate and opadry white.

These are used to manufacture the pills and give them adequate consistency and appearance.

Armour Thyroid Reviews

Online reviews of Armour Thyroid are usually positive.

Many users with hypothyroidism report feeling better on Armour Thyroid compared to levothyroxine. Some people see improvements in weight, hair health, and mood. Users also report experiencing fewer side effects than when they took levothyroxine.

Others have found that levothyroxine controls their TSH lab values better than Armour Thyroid.

A common complaint against Armour Thyroid is the poor availability of the drug, due to reformulations and backorders.

Limitations and Caveats

Despite its long history of use, there is a serious lack of clinical research on desiccated thyroid extracts.

This is due to several reasons.

One factor is the transition to synthetic thyroid hormones as the standard. Almost all clinical trials focus on levothyroxine or other synthetic thyroid hormones.

Another big reason is the fact that Armour Thyroid is not an FDA-approved drug, which makes performing clinical trials difficult.

Natural Thyroid Support

Armour Thyroid is often considered the natural alternative to synthetic thyroid hormones, but it’s unclear if it offers any real benefits.

What we do know is that certain nutrients support thyroid function. Adequate intake of these nutrients is important for thyroid health.

The listed compounds are in no way meant to replace your thyroid medication.

Talk to a doctor before taking supplements alongside prescription medication. Do not change the dosage of your medication or stop taking it without consulting a doctor first.

1) Iodine

Iodine deficiency is one of the leading causes of hypothyroidism [32].

This is because our body uses iodine to create both T3 and T4. Consuming enough iodine in our diet is important in maintaining healthy thyroid hormone levels [32].

Luckily, our diets usually provide adequate amounts of iodine, especially in developed countries [32].

Some foods that are high in iodine include [32]:

  • Seafood
  • Seaweed and kelp
  • Bread
  • Milk
  • Iodized salt

Iodine supplements are also available.

Just remember to stick to the recommended daily intake of 150 micrograms [32].

Too much iodine can have negative effects (triggering autoimmune responses, inflammation, or even low thyroid function). Doses above 1,100 micrograms can even be fatal [33, 34, 32].

2) Tyrosine

Tyrosine is an amino acid that your body uses to create T4 and T3 [35].

Research in sepsis patients suggests that low tyrosine levels reduce thyroid hormone levels [35].

Tyrosine supplements may also help with cognitive performance [36].

If you want to boost tyrosine through your diet, some great sources include [37]:

  • Chicken and Turkey
  • Fish
  • Dairy products
  • Peanuts
  • Bananas

3) Selenium

Selenium is an element your body uses to help convert T4 into T3 [38].

Deficiencies in selenium are also linked to poor immune function and cognitive decline [39].

However, studies examining the benefits of selenium supplements have revealed mixed results [40, 41].

This means the best way to make sure you’re getting enough selenium is probably through our diet. Some selenium-rich foods are [42]:

  • Brazil nuts
  • Garlic
  • Onion
  • Salmon
  • Eggs
  • Beef

4) Vitamin B12

Vitamin B12 plays vital roles throughout the body [43].

Many people with hypothyroidism do not get enough of this vitamin. In fact, up to 40% of people with hypothyroidism may have a vitamin B12 deficiency [44, 17].

A study of 116 people found that vitamin B12 supplements can improve symptoms in hypothyroid patients. This includes improvements to memory, depression, and weakness [17].

5) Thyroid Support Supplements

Many different supplements claim to support thyroid health.

One example is a product called Thyroid Support. These supplements contain a variety of vitamins and nutrients that are important to the thyroid gland, such as iodine, selenium, and vitamin B12.

While these nutrients are essential for thyroid health, studies on supplementation have revealed mixed results [45, 41].

Another class of popular supplement is called Thyroid Glandular or Raw Thyroid. They contain extracts of animal thyroid gland tissue, usually from cows.

These supplements are different from Armour Thyroid. They typically contain no thyroid hormones (T3 or T4), only thyroid gland tissue. They also sometimes include tissues from other glands, like the pituitary or adrenal glands. None have been well studied and it’s questionable if they work [46, 47].

Buy Thyroid Support Supplements

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Takeaway

Once the mainstay treatment for hypothyroidism, Armour Thyroid has largely been replaced with synthetic medications.

Despite this shift in clinical practice, Armour Thyroid still remains in use. Its reliability and safety have yet to be established.

Many people would rather take natural thyroid extracts and report feeling better on them. Armour Thyroid and similar extracts might offer advantages to people with mild (subclinical) hypothyroidism. Some practitioners also generally give natural extracts a preference.

Be sure to talk to a doctor before using Armour thyroid.

About the Author

Mathew Eng, PharmD

PharmD

Mathew received his PharmD from the University of Hawaii and an undergraduate degree in Biology from the University of Washington.

Mathew is a licensed pharmacist with clinical experience in oncology, infectious disease, and diabetes management. He has a passion for personalized patient care and believes that education is essential to living a healthy life. His goal is to motivate individuals to find ways to manage their chronic conditions.

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