Synthroid vs Armour Thyroid

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For patients diagnosed with hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones, certain medications that supplement these hormones can help in restoring normal body metabolism and managing symptoms. Synthroid and Armour Thyroid are two such drugs often prescribed for hypothyroidism. They each provide different forms of thyroid hormone supplementation but both aim to normalize levels in patients with this condition. Synthroid is a synthetic form of thyroxine (T4), one of the primary hormones produced by the thyroid gland. Armour Thyroid, on the other hand, is made from desiccated pig thyroid glands and contains both thyroxine (T4) as well as triiodothyronine (T3), another key hormone produced by the human thyroid gland.

What is Synthroid?

Levothyroxine (the generic name for Synthroid) is a synthetic form of thyroxine, an endogenous hormone secreted by the thyroid gland. It was first approved by the FDA in 1955 and has become one of the most commonly prescribed medications for hypothyroidism. Levothyroxine works by supplementing or replacing depleted levels of thyroid hormones in the body, thereby helping to regulate metabolism and energy production. Unlike Prozac's selective influence on serotonin alone, levothyroxine effectively impacts various physiological processes due to its systemic role as a metabolic regulator.

On the other hand, Armour Thyroid is a natural product made from animal thyroid glands that contains both thyroxine (T4) and triiodothyronine (T3), another important hormone produced by the thyroid gland. This dual action may result in more side effects compared to levothyroxine but can be beneficial for certain patients who do not respond well to T4-only therapy such as Synthroid.

What conditions is Synthroid approved to treat?

Synthroid and Armour Thyroid are both approved for the treatment of underactive thyroid, a condition known as hypothyroidism. They're also used to treat or prevent goiter (enlarged thyroid gland), which can be caused by hormone imbalances, radiation therapy, surgery, or cancer. Additionally:

  • Synthroid is a synthetic form of thyroxine (T4), one of two hormones made by the thyroid gland.
  • Armour Thyroid is made from desiccated pig's thyroid and contains both thyroxine (T4) and triiodothyronine (T3).

How does Synthroid help with these illnesses?

Synthroid works to manage hypothyroidism by increasing the amount of thyroxine (T4) and triiodothyronine (T3) in the body. It does this by supplying synthetic T4, which is converted into T3 in the body's tissues, so levels can be maintained higher for longer periods of time. Thyroxine and triiodothyronine are hormones produced by the thyroid gland that play an essential role in metabolism, growth, development and temperature regulation amongst other things. It is thought that individuals with hypothyroidism have relatively lower levels of these hormones. Therefore, by increasing hormone levels with Synthroid, it can limit the negative effects of hypothyroidism and help patients manage their condition.

Armour Thyroid also treats hypothyroidism but differs from Synthroid as it provides both T3 and T4 derived from desiccated porcine thyroid gland. Some believe this more closely mimics human thyroid function but there's ongoing debate about its effectiveness compared to synthetic options like Synthroid.

What is Armour Thyroid?

Armour Thyroid is a natural product made from animal thyroid glands, specifically pigs. It is used to treat an underactive thyroid (hypothyroidism). It replaces or provides more of a hormone that is usually produced by the thyroid gland, which regulates the body's energy and metabolism. Armour Thyroid has been available since the 1930s, making it one of the oldest drugs for hypothyroidism on the market.

Unlike Synthroid, which only contains T4 (Levothyroxine), Armour Thyroid contains both T4 and T3 (Triiodothyronine). This can be beneficial for some patients who have difficulty converting synthetic T4 into active T3 in their bodies. While its side-effect profile differs from Synthroids', common side effects include increased heart rate, palpitations, sweating and weight loss. However, because it's derived from animals each batch might have slightly different amounts of hormones leading to inconsistent results in patients compared to synthetic levothyroxine like Synthroids'.

What conditions is Armour Thyroid approved to treat?

Armour Thyroid is approved for the treatment of:

  • Hypothyroidism, a condition where the thyroid gland doesn't produce enough thyroid hormones
  • Myxedema coma or precoma, which are extreme forms of hypothyroidism that can be life-threatening if not treated promptly.

How does Armour Thyroid help with these illnesses?

Thyroxine is a hormone that plays a critical role in many bodily functions, including metabolism, heart and digestive function, muscle control, brain development and bone maintenance. As with norepinephrine and serotonin, imbalanced levels of thyroid hormones can have significant impacts on health. Armour Thyroid works by supplementing or replacing the thyroid hormones ordinarily produced by the body. Unlike Synthroid which only contains T4 (levothyroxine), Armour Thyroid includes both T3 (liothyronine) and T4 hormones. This combination of active ingredients may be beneficial for certain patients who are unable to convert levothyroxine into liothyronine efficiently or those who do not respond well to 'typical' synthetic thyroid medications like Synthroid alone due to their unique metabolic needs or genetic makeup.

How effective are both Synthroid and Armour Thyroid?

Both levothyroxine (Synthroid) and desiccated thyroid extract (Armour Thyroid) have established histories of use in the treatment of hypothyroidism, with Synthroid gaining FDA approval years before Armour Thyroid. They work by supplementing or replacing the hormones produced by your thyroid gland, but their compositions differ: Synthroid is a synthetic form of thyroxine (T4), while Armour Thyroid is an animal-based thyroid hormone replacement containing both thyroxine (T4) and triiodothyronine (T3).

The effectiveness of both medications in managing symptoms associated with hypothyroidism has been studied extensively throughout the years. A 2013 randomized crossover study compared levothyroxine to desiccated thyroid extract and found that although there were minor differences in metabolic results, patients reported no preference for either medication based on quality-of-life surveys.

A large-scale observational study conducted over many years indicated that levothyroxine remains effective at alleviating symptoms related to hypothyroidism such as fatigue, weight gain, cold intolerance, constipation and dry skin among others. Levothyroxine is well-tolerated across age groups including elderly populations; however care should be taken when prescribing it alongside other medications due to potential interaction effects.

On the other hand, desiccated thyroid extract like Armour Thyroid might offer benefits for certain patients who do not respond adequately to levothyroxine alone because it contains T3 as well as T4 hormones. However, its use isn't typically considered first-line therapy due to more variable levels of hormonal content than synthetics like Synthroid which can lead to inconsistent dosages if not monitored properly.

abstract image of a researcher studying a bottle of drug.

At what dose is Synthroid typically prescribed?

Oral dosages of Synthroid range from 25-200 mcg/day, but studies have shown that a dose of 1.6 mcg/kg per day is effective for managing hypothyroidism in most people. Children and adolescents may be started on lower doses which can be adjusted based on their weight and TSH levels. In either population, dosage can be increased after a few weeks if there is no response. The maximum daily dose varies depending on individual needs and should not be exceeded without medical advice.

On the other hand, Armour Thyroid dosing ranges typically between 15-120 mg daily but will depend greatly upon individual patient needs as determined by regular thyroid function tests conducted by your doctor. Similar to Synthroid, it's important that patients never exceed the prescribed dosage without consulting with their healthcare provider.

At what dose is Armour Thyroid typically prescribed?

Armour Thyroid treatment is usually initiated at a dosage of 15-30 mg per day. The dose can then be gradually increased by 15 mg increments every 2 to 3 weeks, depending on the patient's response to therapy. A typical maintenance dosage ranges between 60 to 120 mg/day, which may be divided into two doses and taken approximately eight hours apart. If after several weeks there is no significant improvement in symptoms or lab results at this dosage level, it might be necessary for your healthcare provider to increase the daily dose further.

What are the most common side effects for Synthroid?

Common side effects of Synthroid (levothyroxine) include:

  • Increased appetite
  • Weight loss
  • Heat sensitivity
  • Excessive sweating
  • Headache
  • Hyperactivity
  • Nervousness, anxiety and irritability
  • Tremor (shaking)
  • Insomnia (trouble sleeping) -Diarrhea

On the other hand, Armour Thyroid has potential side effects that could include:

  • Hair loss during the first few months of treatment. This effect is usually temporary as your body adjusts to this medication. -Nausea or vomiting may occur. If these effects persist or worsen, tell your doctor promptly. -Increased sweating, sensitivity to heat, mental/mood changes (such as nervousness, mood swings), tiredness, diarrhea are some other common side effects.

Remember to always consult with a healthcare provider for proper diagnosis and treatment options if you experience any adverse reactions from taking medications like Synthroid and Armour Thyroid.

abstract image of a patient experiencing side effect

Are there any potential serious side effects for Synthroid?

While both Synthroid and Armour Thyroid are used to treat hypothyroidism, they may cause different side effects in some patients. For example:

  • Increased or irregular heart rate
  • Signs of allergic reactions: hives, difficulty breathing, swelling in your face or throat
  • Serious symptoms relating to overactive thyroid: increased appetite accompanied by weight loss, increased sweating and heat sensitivity, nervousness or restlessness
  • Changes in menstrual cycles
  • Chest pain or discomfort; shortness of breath; unusual tiredness or weakness.
  • Symptoms indicating an imbalance in electrolytes (like low calcium levels): muscle cramps or stiffness; tremors.

If you experience any such adverse effects after starting either medication regimen - Synthroid (levothyroxine) or Armour Thyroid (desiccated thyroid) - it's important that you seek immediate medical attention.

What are the most common side effects for Armour Thyroid?

When taking Armour Thyroid, certain side effects may occur:

  • Rapid or irregular heartbeat
  • Chest pain or shortness of breath
  • Tremors or restless feeling
  • Sweating and sensitivity to heat
  • Insomnia
  • Changes in menstrual periods
  • Diarrhea, vomiting, appetite changes, weight loss or gain
  • Temporary hair loss (particularly in children during the first month of therapy)
  • Headache

Given that everyone's body reacts differently to medication, it is important for patients to communicate any unusual symptoms with their healthcare provider.

Are there any potential serious side effects for Armour Thyroid?

While Armour Thyroid is often used as a natural alternative to synthetic thyroid medications, it isn't without potential side effects. Some symptoms that may indicate a serious reaction to Armour Thyroid include:

  • Signs of allergic response such as hives, itching, fever or swollen glands
  • Trouble breathing, swelling in your face or throat which could be signs of anaphylaxis
  • Chest pain or rapid/irregular heartbeat indicating potential cardiovascular issues
  • Extreme fatigue or restlessness suggesting imbalances in your thyroid hormone levels
  • Unusual mood swings and confusion leading towards altered behavior
  • Temporary hair loss during the first few months of treatment

If you notice any of these symptoms while taking Armour Thyroid, seek immediate medical attention.

Contraindications for Synthroid and Armour Thyroid?

Synthroid and Armour Thyroid, along with other thyroid hormone replacement medications, may exacerbate symptoms in some people with heart disease. If you notice your heart condition worsening, or experiencing an increase in chest pain or palpitations, please seek immediate medical attention.

Neither Synthroid nor Armour Thyroid should be taken if you are taking certain types of antidiabetic drugs like insulin or oral hypoglycemics. Always tell your physician which medications you are taking; adjustments to the dosage of these diabetic medicines might be required when starting on a thyroid medication regimen to prevent dangerous interactions with Synthroid and Armour Thyroid.

Thyroid hormones including both Synthroid and Armour Thyroids must not be used for weight control as they can pose serious risks such as loss of bone density especially at higher doses. Use caution while switching from one brand to another (such as from Synthroid to Armour) due its individual variability in drug concentration.

How much do Synthroid and Armour Thyroid cost?

For the brand name versions of these thyroid medications:

  • The price for 30 tablets of Synthroid (100 mcg) averages around $45 which works out to approximately $1.50/day.
  • The cost for 30 capsules of Armour Thyroid (60 mg) is about $27, working out to nearly $0.90/day.

Therefore, if you're taking a typical dosage for hypothyroid treatment with Synthroid (i.e., 100 mcg/day or higher), then brand-name Armour Thyroid could be less expensive on a per-day treatment basis. However, always keep in mind that cost should not be the sole determining factor when choosing between these two medications.

For generic versions of Synthroid (levothyroxine) and Armour Thyroid (desiccated thyroid extract), costs are considerably lower:

  • Levothyroxine is available in packs ranging from 30 to 90 tablets, with approximate costs starting as low as $10 for a month's supply, translating to roughly $.33/day at most common dosages.
  • Desiccated thyroid extract can also range widely in price depending on your pharmacy; however, it generally remains cheaper than its branded counterpart - usually under $.60/day.

It should be noted that while both drugs serve similar purposes they contain different forms of hormones and may affect individuals differently; thus consultation with healthcare professionals before deciding on medication is essential.

Popularity of Synthroid and Armour Thyroid

Levothyroxine, available in generic form and under brand names such as Synthroid, was estimated to have been prescribed to about 104.7 million people in the US in 2016. Levothyroxine accounted for a significant percentage of prescriptions for hypothyroidism treatment in the US. It is one of the most commonly used thyroid hormones due to its efficacy and predictable absorption.

On the other hand, desiccated thyroid extract (DTE), including brand versions like Armour Thyroid, had significantly fewer prescriptions filled compared to levothyroxine. In recent years there has been increased interest in DTE as an alternative therapy for hypothyroidism though it hasn't surpassed levothyroxine's popularity yet. This is partly due to concerns about variability between batches and potential allergenicity from porcine-derived content which makes some medical professionals hesitant to prescribe it even if patients express preference based on anecdotal reports of improved symptoms with DTE use compared to synthetic thyroids.


Both Synthroid (levothyroxine) and Armour Thyroid have established records in the treatment of hypothyroidism, with numerous clinical studies indicating their efficacy over placebo treatments. The two drugs may sometimes be combined for therapeutic reasons, but such combinations must be carefully monitored by a healthcare provider due to potential drug interactions. Their mechanisms of action differ: Synthroid is synthetic T4 hormone which gets converted into T3 in the body as needed, while Armour Thyroid contains both T4 and T3 hormones derived from porcine thyroid glands.

Synthroid is generally considered the first-line treatment option, whereas Armour Thyroid might be used as an adjunct therapy or in patients who haven't responded optimally to levothyroxine alone or have specific intolerance issues.

Both medications are available in generic form — levothyroxine for Synthoid and desiccated thyroid extract for Armour Thyroid— representing significant cost savings especially for patients paying out of pocket. Both may require an adjustment period as optimal dosing is determined based on individual patient response.

The side effect profile between the two drugs can vary given different individuals' reactions to synthetic versus animal-derived hormones; however, both are generally well-tolerated when administered at appropriate doses. For both medications, patients should closely monitor their symptoms and seek medical attention if they notice worsening fatigue, weight changes, mood swings or other signs indicative of improper hormone balance.