Research suggests that tens of millions of Americans suffer from hypothyroidism or underactive thyroid. Two of the most popularly prescribed treatments for hypothyroidism include: Armour Thyroid (porcine-derived desiccated thyroid extract) and Synthroid (levothyroxine). Armour Thyroid is classified “natural” in that it is thyroid hormone extracted from pigs, whereas Synthroid is considered “artificial” in that it is a synthetically engineered chemical.
There is much controversy surrounding Armour Thyroid and Synthroid, especially when compared head-to-head. Advocates of Armour Thyroid suggest that since it is “natural” it is likely more biologically compatible with humans than a synthetic thyroid replacement. On the other hand, proponents of Synthroid highlight the fact that it has gone through rigorous clinical testing necessary for FDA approval and is considered safe and effective in humans.
It is important to avoid automatically assuming that one thyroid replacement therapy is utopian and/or universally superior to the other. Certain individuals may respond better to Armour Thyroid, while others may derive significantly more therapeutic benefit from Synthroid. Understanding how these interventions compare on a head-to-head basis may be helpful if you’re struggling to decide which treatment to pursue.
Armour Thyroid vs. Synthroid Comparison (Chart)
Below is a chart comparing the basic attributes of Armour Thyroid with Synthroid. As you can see, both medications have similar medical uses, are manufactured by pharmaceutical companies, and are available on a “prescription-only” basis. That said, Synthroid has attained FDA approval whereas Armour Thyroid was never formally approved.
Armour Thyroid vs. Synthroid
|Ingredients||Porcine-Derived Desiccated Thyroid Extract||Levothyroxine (L-Thyroxine)|
|Drug classification||Natural T4/T3 (4:1 ratio)||Synthetic T4 (100%)|
|Approved medical uses||Hypothyroidism. Goiter. Nodular Thyroid Disease. Thyroid Cancer.||Hypothyroidism. Goiter. Nodular Thyroid Disease. Thyroid Cancer.|
|Formats||Oral tablets.||Oral tablets.|
|Dosages||15 mg. 30 mg. 60 mg. 90 mg. 120 mg. 180 mg. 240 mg. 300 mg.||25 mcg. 50 mcg. 75 mcg. 88 mcg. 100 mcg. 112 mcg. 125 mcg. 137 mcg. 150 mcg. 175 mcg. 200 mcg. 300 mcg.|
|Manufacturer||Actavis Pharmaceuticals Inc.||AbbVie Inc.|
|Mechanism of action||Mimics neurophysiological effects of endogenously manufactured T4 (thyroxine) and T3 (triiodothyronine). |
Modulates DNA transcription, protein synthesis, basal metabolic rate, tissue oxygenation, and lipolysis.
|Mimics neurophysiological effects of endogenously manufactured T4 (thyroxine).
Modulates DNA transcription, protein synthesis, basal metabolic rate, tissue oxygenation, and lipolysis.
|Generic version (?)||No.||Yes.|
|Half-Life||6 to 7 days (T4)||6 to 7 days (T4)|
|Common side effects||Appetite changes. Nervousness. Hair loss. Headaches. Weight loss. (Read: Armour Thyroid side effects).||Appetite changes. Nervousness. Hair loss. Headaches. Weight loss. (Read: Synthroid side effects).|
|Date approved||N/A (Unapproved)||2002|
Cost: Which is more expensive?
In regards to cost, there isn’t a significant difference in price for a 30-day supply of Armour Thyroid and Synthroid. For 30 tablets of low-dose (15 mg) Armour Thyroid, it’ll cost around $17 – which is relatively cheap. If you’re taking high-dose (300 mg) Armour Thyroid, it’ll cost over $50 for a month’s supply – which is slightly more expensive.
Individuals taking low-dose (25 mcg) Synthroid will end up spending around $35 for a 30-day supply. Compared to the low-dose of Armour Thyroid, the low-dose Synthroid is nearly double the cost. However, a 30-day supply of the highest dosage of Synthroid (300 mcg) can be purchased for around $45 – which is slightly less than the highest dose of Armour Thyroid.
From a pricing perspective, 30 tablets of the lowest dose (15 mg) Armour Thyroid is cheaper at $17 than 30 tablets of the lowest dose (25 mcg) Synthroid at $35. At the dosage increases such as at the highest respective dosages, Synthroid (300 mcg) ends up being a slightly better bargain at $45 for a 30-day supply than Armour Thyroid (300 mg) exceeding $50.
It is important to note that unlike Armour Thyroid, a generic version of Synthroid is available. Generic Synthroid, commonly referred to as “levothyroxine” can be purchased for a fraction of the price of the brand name version. For an entire month supply of levothyroxine, users typically end up spending between $4 and $10; this is very cheap.
Assuming you want to maximize your overall savings and/or are on a tight budget, generic Synthroid sold as “levothyroxine” is the best deal. That said, even the “brand name” versions of Armour Thyroid and Synthroid aren’t too expensive for most. While it doesn’t make sense to base medication choice solely on price, generic levothyroxine is the lowest-cost of these options.
Dosage & Formats
Both Armour Thyroid and Synthroid are sold only in tablet (pill) format for oral administration. Upon comparison, it appears that there are 12 total dosing options for Synthroid and only 8 dosing options for Armour Thyroid. Armour Thyroid is manufactured in tablets of: 15 mg, 30 mg, 60 mg, 90 mg, 120 mg, 180 mg, 240 mg, and 300 mg.
Synthroid is manufactured in tablets of: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, and 300 mcg. Since it is often difficult to calibrate optimal dosages for the treatment of hypothyroidism, the greater the number of total dosing options, the more precise doctors can be with their prescriptions. Slight alterations in dosing are more convenient with Synthroid (e.g. jumping from 75 mcg to 88 mcg pills) than Armour Thyroid (e.g. jumping from 60 mg to 90 mg pills).
A greater number of dosing options allows patients to ingest a full pill to modulate TSH, T4, and T3 levels – without having to worry about splitting and/or taking multiple pills. From the perspective of available manufactured dosages, Synthroid should be considered slightly advantageous. That said, most patients can learn to use a pill cutter to optimally calibrate Armour Thyroid dosages.
Efficacy: Which is more effective?
When comparing thyroid replacement therapies of Armour Thyroid and Synthroid, it is necessary to consider whether one intervention may be more effective than the other. Synthroid has undergone extensive clinical testing for the treatment of hypothyroidism and has been considered clinically effective since 2002 by the FDA. To attain FDA approval, Synthroid had to demonstrate significant therapeutic efficacy for the treatment of hypothyroidism compared to a placebo in randomized controlled trials (RCTs).
Unlike Synthroid, formulations of Armour Thyroid (desiccated thyroid extract) have not been formally evaluated by the FDA. Due to the lack of clinical testing, the efficacy of Armour Thyroid as a treatment for hypothyroidism should be questionable. While desiccated thyroid extracts have been utilized extensively throughout history as a natural thyroid replacement therapy, they haven’t been subjected to the same rigorous FDA evaluation as Synthroid.
Despite the lack of randomized controlled trials to elucidate the clinical efficacy of Armour Thyroid, it has been a part of head-to-head comparative research with Synthroid. There is some evidence to suggest that Armour Thyroid is equally as effective as Synthroid for the treatment of hypothyroidism. Most medical professionals acknowledge that each intervention is capable of optimizing TSH, T4, and T3 concentrations.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/23539727
Mechanism of action
Both Armour Thyroid and Synthroid function by elevating physiological concentrations of thyroid hormones. Armour Thyroid is formulated as a natural blend of T4 (thyroxine) and T3 (triiodothyronine). Treatment with Armour Thyroid is capable of optimizing levels of T4, T3, and TSH – possibly to the same extent as Synthroid.
Synthroid is a synthetic version of T4 (thyroxine) known as levothyroxine, and unlike Armour Thyroid, it does not directly increase T3. Ingestion of Synthroid mimics the endogenous effects of T4, which gets converted to T3. Treatment with the proper dosage of Synthroid is capable of normalizing T4, T3, and TSH levels.
There is some evidence to support the idea that Armour Thyroid may elevate T3 (triiodothyronine) to a supraphysiologic extent due to the fact that it is manufactured at a 4:1 ratio of T4 to T3. In humans, the endogenously secreted ratio of T4 to T3 is thought to be ~11:1; Armour Thyroid is a mismatch with this ratio. That said, Armour Thyroid and Synthroid are thought to elicit similar effects, thereby reversing neurophysiological abnormalities associated with hypothyroidism.
The mechanism of action of each thyroid replacement is thought to improve: DNA transcription, protein synthesis, basal metabolic rate, tissue oxygenation, and lipolysis. For this reason, users often report feeling more energetic, cognitive improvement (especially in memory functions), and mood enhancement. It is possible that slight nuances in respective mechanisms of action could facilitate superior efficacy with one thyroid replacement over the other [in a subset of users].
Armour Thyroid and Synthroid are principally utilized as medical treatments for hypothyroidism. That said, they are also sometimes used as interventions for the treatment of goiter, nodular thyroid disease, and thyroid cancer. Each treatment is capable of increasing concentrations of T4 (thyroxine) and T3 (triiodothyronine), thereby reversing symptoms of hypothyroidism.
As T4 and T3 concentrations increase with Armour Thyroid or Synthroid treatment, the amount of TSH (thyroid stimulating hormone) as generated by thyrotope cells in the anterior pituitary gland decreases. Reducing TSH concentrations can improve cases of thyroid goiter, nodular thyroid disease, and thyroid cancer. Medically, both Armour Thyroid and Synthroid are utilized as treatments for similar conditions.
Data suggests that over 20 million prescriptions are filled for Synthroid annually. There is no data available on the number of Armour Thyroid prescriptions, but it is likely prescribed considerably less than Synthroid. Synthroid has retained popularity in the United States due to the fact that it is approved by the FDA and considered both safe and effective over a long-term.
Armour Thyroid is less popular because it has not been subject to the same degree of clinical testing as Synthroid. There is no FDA stamp of approval to support the safety and efficacy of Armour Thyroid over a long-term for the treatment of hypothyroidism. For this reason, many endocrinologists and medical professionals advise against the usage of Armour Thyroid – ultimately making it a less popular option.
Commonly reported side effects and adverse reactions associated with Armour Thyroid and Synthroid are thought to be similar. Each thyroid replacement therapy tends to provoke side effects such as: appetite changes, hair loss, headaches, nervousness, and weight loss. These side effects are most often reported during the first 3 months (90 days) of treatment and often diminish and/or subside thereafter.
Improperly calibrated dosing can make side effects likely with either intervention. Both Armour Thyroid and Synthroid have a narrow therapeutic index (NTI) associated with dosing. If the administered dosage is slightly too high, patients are likely to report noticeable side effects. If the administered dosage is substantially higher than necessary, side effects may be severe.
The American Association of Clinical Endocrinologists and the Royal College of Physicians suspect that unwanted side effects may be more likely to occur among users of Armour Thyroid than Synthroid for several reasons. Reasons Armour Thyroid may provoke more side effects include: ratio of T4 to T3 (differing significantly from endogenous ratios in humans), inter-batch variability (batches and/or ingredients may be modified), and the lack of clinical trials for FDA approval. The ratio of T4 to T3 alone (at 4:1) may result in supraphysiological levels of T3, which could trigger unwanted side effects.
That said, a 2013 comparative study noted that many “patients preferred” Armour Thyroid over Synthroid for the treatment of hypothyroidism. The comparative study discovered that side effects didn’t significantly differ between the two interventions other than weight loss. Those taking Armour Thyroid were likely to experience moderate weight loss (~3 lbs), whereas those taking Synthroid did not lose weight.
Most scientific literature does not suggest a marked difference between the two interventions in terms of side effects and overall tolerability. However, other experts believe that Synthroid is likely to trigger more side effects than Armour Thyroid due to the fact that it is artificial (synthetic). As a result of its synthetic status and biological incompatibility, human cells respond differently to Synthroid than endogenous thyroid and it may provoke more side effects than Armour Thyroid.
In summary, side effects of Armour Thyroid and Synthroid do not appear to differ based on clinical research. However, there may be significant interindividual differences in terms of tolerability. Like any intervention, certain individuals may experience less side effects with Armour Thyroid than Synthroid and vice-versa.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/23539727
Similarities: Armour Thyroid vs. Synthroid (List)
Below is a recap of similarities between Armour Thyroid and Synthroid. Both drug appear to be similar in cost, efficacy, and side effects. In addition, each substance is utilized as a treatment for similar medical conditions.
- Cost: The brand name version of either intervention (Armour Thyroid and Synthroid) is of similar cost. The price range for a 30-day supply of Armour Thyroid is between $17 and $52, whereas that for a 30-day supply of Synthroid is $35 to $45 dollars. Assuming you only buy “brand name” substances, both should be considered comparable.
- Efficacy: There is no definitive evidence to suggest that one intervention is more effective than the other. While there is data to prove the clinical efficacy of Synthroid, there isn’t data to disprove the clinical efficacy of Armour Thyroid. In head-to-head comparison studies, each intervention appeared to exhibit equal efficacy in reducing symptoms of hypothyroidism.
- Legal status: Armour Thyroid and Synthroid are both considered prescription-only (Rx-only) thyroid replacement therapies. Neither are classified as controlled-substances, but neither are available as over-the-counter (OTC) agents. To attain either Armour Thyroid or Synthroid, you will need a prescription from a medical professional.
- Medical uses: Both agents (Armour Thyroid and Synthroid) are used medically for the treatment of hypothyroidism. They are each also commonly prescribed for thyroid goiter, nodular thyroid disease, and thyroid cancer. Similarities in medical uses makes logical sense due to the fact that both agents attempt to increase thyroid concentrations.
- Side effects: Evidence suggests that side effects of Armour Thyroid and Synthroid are relatively similar. Each agent can cause: appetite changes, hair loss, nervousness, and weight changes. While side effects may differ based on the specific user, overarching side effect profiles between the two drugs is remarkably similar.
Differences: Armour Thyroid vs. Synthroid (List)
There are some notable differences between Armour Thyroid and Synthroid as a treatment for hypothyroidism. Key differences between the two treatments include: FDA approval status, formatting (natural vs. synthetic), and popularity. Some believe that specific differences may make one agent more advantageous than the other.
- Dosages: There are a greater number of manufactured dosages associated with Synthroid than Armour Thyroid. Synthroid is sold in 12 precisely-dosed tablets, whereas Armour Thyroid is only manufactured in 8 precisely-dosed tablets. Some may regard the 4 extra dosages of Synthroid as being preferable over Armour Thryoid.
- FDA approval: Synthroid was approved in July 2002 for the treatment of hypothyroidism. Prior to its approval, it was extensively evaluated for safety and efficacy in randomized controlled trials. Armour Thyroid cannot be patented, and as a result, will never receive the formal FDA “stamp of approval”; this is a cause of concern for some practitioners.
- Format: The formatting of Armour Thyroid and Synthroid is substantially different. While each is sold as an “oral” tablet, the Armour Thyroid is “natural” and the Synthroid is “synthetic.” Many individuals believe that the natural form of thyroid (Armour Thyroid) is of superior biological tolerability.
- Generic availability: Synthroid is manufactured as the generic chemical “levothyroxine” whereas Armour Thyroid is not available as a generic. Many individuals prefer generic drugs for the fact that they are considerably less expensive than the “name brand” versions. Levothyroxine is only $4 to $10 for a 30-day supply, making it more appealing than Armour Thyroid in terms of cost.
- Manufacturer: Armour Thyroid is currently manufactured by Actavis, Inc. (rights were acquired from Forest Laboratories, Inc.), whereas Synthroid is manufactured by AbbVie, Inc. Alterations in the manufacturer of Armour Thyroid (from Forest to Actavis) have lead some consumers to complain, suggesting that minor ingredient adjustments have reduced the efficacy of the product. Synthroid’s manufacturer has remained constant and hasn’t been subject to ingredient tweaks since its inception.
- Popularity: Upon comparison of the two thyroid replacement therapies, Synthroid is immensely more popular than Armour Thyroid. While Armour Thyroid is still a popular intervention, it is not commonly recommended by medical professionals and endocrinologists (due to lack of FDA approval). For this reason, patients with hypothyroidism are most frequently prescribed Synthroid. Synthroid is considered one of the top prescribed pharmaceutical drugs in the United States.
- Thyroid stimulation: Regardless of whether an individual is using Armour Thyroid or Synthroid, the goal is to normalize T4/T3 and TSH concentrations. That said, Armour Thyroid delivers a natural blend of T4 and T3 at a 4 to 1 ratio, whereas Synthroid delivers solely synthetic T4 without directly providing T3. As a result of formatting differences and the combined T4/T3 in Armour Thyroid compared to just T4 in Synthroid, degree of thyroid stimulation differs.
- Weight loss: Although it is common for patients to report weight loss with Armour Thyroid, it may be slightly less common to lose weight with Synthroid. A head-to-head comparative study (Armour Thyroid and Synthroid) suggests that modest weight loss only occurred among users of Armour Thyroid. If you’re taking Synthroid, you may be less likely to more likely to remain “weight neutral” throughout your treatment.
Which drug is “better” for hypothyroidism?
Everyone wants to know whether Armour Thyroid is “better” than Synthroid or vice-versa. Some medical professionals advise against using Armour Thyroid because they do not believe there is adequate evidence from randomized controlled trials (RCTs) to support its long-term safety and efficacy. Other professionals speculate that there may be greater biological risk and/or deleterious effects associated with long-term administration of Synthroid, primarily because it is synthetic.
There is no clear-cut answer in regards to whether one thyroid replacement option is superior to the other. Comparative head-to-head research indicates that both interventions are capable of significantly reducing symptoms of hypothyroidism. Furthermore, both interventions appear to have similar side effect profiles and are generally well-tolerated by patients when dosages are properly calibrated to normalize T4, T3, and TSH.
One study documented that among patients that tested both therapies, ~48% expressed preference for Armour Thyroid over Synthroid; the remaining individuals didn’t seem to prefer one over the other. Preference for Armour Thyroid over Synthroid may indicate that it has slightly lower propensity to induce side effects and/or is slightly more effective. That said, there is zero evidence to scientifically imply that one therapy is more efficacious and/or more tolerable than the other.
Despite no general scientific differences between the two thyroid replacement options in terms of efficacy and tolerability, interindividual differences should not be discounted. Consider drugs of any classification such as antidepressants. Although all FDA-approved antidepressants are considered clinically effective and well-tolerated for the treatment of depression, efficacy and tolerability are not apparent in every single user; there is significant interindividual variability.
For this reason, if you want to know whether Armour Thyroid is better than Synthroid, you’ll likely need to conduct an experiment and test both to determine whether one is better suited for your particular neurophysiology. Testing each for a 4-month period will give you a good idea as to whether one option is more effective and/or less likely to trigger unwanted side effects [for you]. After testing both options, you may find that: both are equally effective and tolerable, one is more effective and/or tolerable than the other, or that neither are very tolerable.
If you don’t give each an adequate test through, you’ll be left wondering whether the other option may superior to your current therapy. Also keep in mind that the thyroid replacement therapy that is ideal for your neurophysiology may be a poor fit for someone else; you may like Armour Thyroid, but another person may be unable to tolerate it. Work with a medical professional to trial both Armour Thyroid and Synthroid to find what works best for you.
Which drug do you prefer: Armour Thyroid or Synthroid?
Many individuals have taken the time to test both Armour Thyroid and Synthroid for the treatment of hypothyroidism. If you’ve tried both options, leave a comment mentioning whether you found one option to be superior than the other in terms of efficacy and/or tolerability. Which thyroid replacement therapy do you believe is safer for long-term usage in humans and why?
If you found both Armour Thyroid and Synthroid to be of equal efficacy for the treatment of your hypothyroidism, were there any noticeable differences in side effects that you experienced? Understand that it is ultimately up to you to work with a professional to determine the safest, sustainable treatment for hypothyroidism. For some individuals the best option may be Armour Thyroid, while for others the better bet is Synthroid.