Over 100 years ago, doctors started making extracts from the dried, ground-up thyroid glands of pigs to treat thyroid disorders. Uncover the unique history of Armour Thyroid and find out how it compares to modern treatments such as levothyroxine.
Armour Thyroid is the brand name for a naturally-derived medication called desiccated thyroid extract. Other brand names include NP Thyroid and Nature-Throid. Although all of these thyroid extract medications require a prescription, they are not approved by the FDA.
These extracts are made from the thyroid glands of animals, typically from pigs. The thyroid glands are first dried and turned into a powder (“desiccated”). They are then packaged into ready-to-use products .
Many different organizations, including the American Association of Clinical Endocrinologists and the European Thyroid Association, recommend against the use of thyroid extracts, including Armour Thyroid [4, 5].
Thyroid hormone replacement (such as Armour Thyroid) is used when people cannot produce enough thyroid hormones on their own, a condition called hypothyroidism .
Armour Thyroid contains T3 and T4 that is extracted from pigs. These animal thyroid hormones work similarly in humans and can help restore thyroid hormone levels .
The first recorded use of desiccated thyroid extract was in 1891. After that, animal extracts quickly became the standard treatment for hypothyroidism .
Even after synthetic versions of T4 and T3 were developed, thyroid extracts remained the preferred choice for a while. These animal 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 .
However, several key discoveries changed how most doctors viewed thyroid extracts .
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 .
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 .
Another issue is the inconsistent quality of thyroid extract products. Multiple studies have shown that the contents inside animal thyroid extracts can vary wildly. The quality of these thyroid extracts is also not monitored by the FDA [1, 7].
Over time, these discoveries prompted a major shift towards the use of levothyroxine, a synthetic T4 medication .
Armour Thyroid is not approved by the FDA. The safety and effectiveness of Armour Thyroid have not been evaluated for any use.
Armour Thyroid is primarily used to treat low thyroid hormone levels (hypothyroidism). It provides animal-derived thyroid hormones (T4 and T3), which the body can use for itself .
Desiccated thyroid extracts, like Armour Thyroid, have been used historically to replenish thyroid hormones in humans, Despite this, very few studies have evaluated their effectiveness .
In a randomized crossover trial of 70 patients with hypothyroidism, thyroid extract caused modest weight loss and was preferred by more patients compared to levothyroxine.
However, an analysis of 13 clinical trials and 4 systematic reviews concluded that combination therapy with T3 and T4 is not better than levothyroxine alone .
Levothyroxine is a synthetic version of T4, which is converted to T3 by the body. In contrast, Armour Thyroid contains T4 and T3 that are extracted from pigs .
Armour Thyroid contains T4 and T3 in about a 4:1 ratio .
However, human thyroid glands naturally secrete T4 and T3 in a 14:1 ratio .
One of the main reasons thyroid extracts fell out of favor was because of inconsistent product quality .
Today, the consistency of these products has improved and they are more standardized. However, their content is still more likely to vary compared to synthetic drugs like levothyroxine .
Although Thyroid extracts are regulated by the FDA, they are not actually an FDA-approved medication.
This is partly because desiccated thyroid extracts existed before the formation of the FDA, so they never went through the drug approval process .
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.
Many organizations, like the American Thyroid Association and the American Association of Clinical Endocrinologists, recommend against the use of desiccated thyroid extracts in pregnancy .
One major issue is that the safety of thyroid extracts has never been studied in pregnancy .
Armour Thyroid is not approved by the FDA. The safety of Armour Thyroid is unknown due to a lack of clinical research. Always take your medication as directed by your doctor.
The side effects of Armour Thyroid have not been evaluated by clinical trials or the FDA. If you are taking Armour Thyroid and any side effects persist or worsen, let your doctor know. This is not a complete list of possible side effects. Tell your doctor if you experience any serious side effects or notice any effects not listed here.
Some common side effects of thyroid hormone replacement include :
Some serious side effects of thyroid hormone replacement include :
- Mood or mental changes
- Shortness of breath
- Chest pain
- Irregular heartbeat
- Swelling in the hands, ankles, or feet
Often, side effects are due to imbalances in thyroid hormones and not from the medication itself. If thyroid hormone levels are within normal range, side effects are usually uncommon .
Some symptoms of high thyroid hormone levels include :
- Appetite changes
- Difficulty sleeping
Armour Thyroid is generally not recommended during pregnancy .
This is mostly due to a lack of research – no studies have looked at the safety of desiccated thyroid extracts in pregnancy .
Another issue is that desiccated thyroid extracts contain lower concentrations of T4 compared to levothyroxine. Research suggests that adequate T4 levels are crucial for fetal brain development [11, 8].
If you are pregnant or plan to become pregnant, it’s best to discuss treatment options with your doctor.
- 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 manufacturer’s product label
The following drugs have been reported to interact with Armour Thyroid. However, this is not a complete list, let your doctor know of all the medications you are currently taking to avoid any unexpected interactions.
Some potential interactions include [17*]:
*Based on manufacturer’s product label
There is a case report of a male adult experiencing a heart attack after using testosterone and Armour Thyroid together. The man was using the two medications in order to lose weight and gain muscle .
The dosing of Armour Thyroid can vary. Always take this medication as directed by a doctor.
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 .
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 .
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.
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.