If you take thyroid medication, you may have noticed that there are **a lot of different options**—and they aren’t all the same. Some contain only T4, some contain both T4 and T3, and some are derived from animal thyroid while others are manufactured to be chemically identical to the hormones our bodies produce.
The good news is that there isn’t one thyroid medication that is right for every patient. At Living Wellness Medical Center, we look at your **symptoms, thyroid labs, medical history, response to treatment, and personal preferences** when deciding which option may be best for you.
Another consideration that sometimes gets overlooked is the **inactive ingredients, or excipients**, in thyroid medications. These can include fillers, binders, dyes, lactose and other ingredients that don’t provide thyroid hormone but help make the tablet or capsule. Most people tolerate these ingredients without any difficulty, but patients with food sensitivities, allergies, celiac disease or gastrointestinal issues may want to pay closer attention to the formulation they take.
First, What Are T4 and T3?
Your thyroid primarily produces a hormone called **T4 (thyroxine)**. Think of T4 as a relatively stable “storage” form of thyroid hormone. Your body then converts T4 into **T3 (triiodothyronine)**, the more biologically active form of thyroid hormone that acts on tissues throughout the body.
This distinction is important because thyroid medications generally fall into three categories:
T4 alone → T4 + T3 together → Desiccated thyroid containing both T4 and T3.
Let’s look at the differences.
Levothyroxine: The Traditional T4-Only Approach
Examples: Synthroid®, Levoxyl®, Unithroid® and generic levothyroxine**
Levothyroxine contains **T4 only** and is the standard first-line treatment for hypothyroidism. Although it is manufactured rather than animal-derived, levothyroxine is chemically identical to the T4 hormone produced by the human thyroid. Your body then converts that T4 into active T3 as needed.
Potential Pros
- Long history of use and extensive research
- Long-acting and generally easy to dose once daily
- Available in many strengths
- Generic versions can be inexpensive
- Usually widely covered by insurance
- Allows the body to regulate the conversion of T4 into T3
Potential Cons
- Some patients continue to experience hypothyroid symptoms despite having a “normal” TSH
- Absorption can be affected by food, supplements and certain medications
- Calcium and iron can significantly interfere with absorption and generally need to be separated from the medication
- Acid-suppressing medications, including proton pump inhibitors (PPIs), can affect the absorption of traditional levothyroxine tablets
- Switching between generic manufacturers may introduce differences in inactive ingredients
- Some patients simply feel better when their treatment includes T3
What About Gluten, Lactose, Dyes and Other Fillers?
Not all levothyroxine tablets have the same inactive ingredients. This can be important for sensitive patients.
For example, **Synthroid is labeled as containing no ingredients derived from gluten-containing grains**, but it does contain **lactose, acacia, confectioner’s sugar containing corn starch, magnesium stearate, povidone and talc**. Most Synthroid strengths also contain one or more color additives; the **50 mcg tablet is an exception and does not contain a color additive**.
**Levoxyl is also labeled gluten-free**, but has its own combination of inactive ingredients and some strengths contain color additives.
Generic levothyroxine formulations can vary by manufacturer, so the excipients in one generic tablet may not be identical to another. For patients with significant sensitivities, it’s worth looking at the **specific manufacturer and formulation**, rather than simply assuming all levothyroxine is the same.
For many people, traditional levothyroxine works extremely well and remains the **standard first-line treatment for hypothyroidism**.
Tirosint®: A T4 Option Designed for Consistent Absorption
Tirosint® is also **levothyroxine (T4)**, but unlike traditional levothyroxine tablets, it comes in a **liquid-filled soft-gel capsule with very few inactive ingredients**
One of the biggest potential advantages of Tirosint is **more predictable absorption**.
Traditional thyroid tablets have to dissolve in the stomach before the medication can be absorbed. Changes in stomach acidity, food, gastrointestinal conditions and certain medications can interfere with that process.
Tirosint’s soft-gel formulation may make absorption **less dependent on stomach acidity**. This can be particularly helpful for people taking **proton pump inhibitors (PPIs)** or other acid-reducing medications, which can sometimes interfere with absorption of traditional levothyroxine tablets.
Tirosint may also be **less sensitive to some food-related absorption issues** than conventional levothyroxine tablets. While we still recommend following your physician’s instructions regarding timing of your thyroid medication, this formulation may provide more consistent thyroid levels for some patients whose absorption varies with traditional tablets.
Another significant advantage for sensitive patients is its **very short inactive-ingredient list**. The Tirosint soft-gel capsule contains levothyroxine along with only a few additional ingredients rather than the longer list of fillers, binders and dyes found in many tablets. This can make it an appealing option for patients who are sensitive to **lactose, gluten-containing ingredients, dyes or other common tablet excipients**.
Potential Pros
- **Excellent and potentially more consistent absorption**
- May be helpful for patients with **GI or absorption issues**
- Absorption may be **less affected by PPIs and reduced stomach acid**
- May be **less sensitive to food-related absorption issues** than traditional levothyroxine tablets
- Very few inactive ingredients
- No tablet dyes or many of the fillers commonly found in traditional tablets
- May be especially useful for patients with **multiple food or medication sensitivities**
- Provides the same T4 hormone as traditional levothyroxine in a different delivery system
Potential Cons
- It is still a **T4-only medication**, so it does not provide T3 directly
- It can be more expensive than generic levothyroxine
- Insurance coverage varies and some plans may require prior authorization
For someone whose thyroid levels fluctuate despite taking levothyroxine consistently—or who has digestive, absorption or excipient-sensitivity concerns—**Tirosint can be an excellent option to discuss before assuming that T4 therapy itself isn’t working.**
Desiccated Thyroid: Armour Thyroid® and NP Thyroid®
**Armour Thyroid® and NP Thyroid® are desiccated thyroid extract (DTE) medications.** Rather than containing T4 alone, they are made from porcine thyroid and naturally contain **both T4 and T3**.
This is one of the biggest reasons some patients prefer these medications.
Potential Pros
- Provides both **T4 and T3 in one medication**
- Some patients report feeling better on a T3-containing medication
- May be an option for patients who continue to experience symptoms despite adequate T4 therapy
- Convenient way to receive both thyroid hormones in a single prescription
- Long history of clinical use
Potential Cons
- The ratio of T4 to T3 is fixed and differs from the ratio normally produced by the human thyroid
- Desiccated thyroid provides proportionally more T3 than the human thyroid normally secretes
- Because T3 is shorter-acting, blood levels can rise after taking a dose and then decline during the day
- Too much T3 can cause symptoms such as **palpitations, anxiety, tremor, sweating or insomnia**
- Excessive thyroid replacement over time can negatively affect **heart rhythm and bone health**
- Insurance coverage, cost and availability can vary
Desiccated thyroid is not generally considered the conventional first-line treatment for hypothyroidism, but **some patients feel and function very well on it**. This is where individualized thyroid treatment becomes important.
Armour Thyroid® vs. NP Thyroid®: What’s the Difference?
Patients frequently ask whether Armour Thyroid and NP Thyroid are completely different medications.
They are actually quite similar. **Both are porcine-derived desiccated thyroid medications containing T4 and T3.** The primary differences involve the manufacturer, formulation and inactive ingredients.
This is another area where excipients may matter.
**NP Thyroid has a relatively short inactive-ingredient list**—calcium stearate, dextrose and mineral oil—and its current manufacturer labeling states that it contains **no ingredient made from gluten-containing wheat, barley or rye. It is also dye-free.**
**Armour Thyroid has a somewhat longer inactive-ingredient list**, including calcium stearate, dextrose, microcrystalline cellulose, sodium starch glycolate and a tablet coating. Therefore, even though Armour and NP Thyroid provide similar thyroid hormones, a particularly sensitive patient may tolerate one formulation differently than the other.
Someone who has done well on NP Thyroid may therefore be able to discuss Armour Thyroid as an alternative with their physician. However, we don’t recommend simply substituting one thyroid prescription for another without medical guidance.
Even when two medications appear similar, **changing the product or dose can change your thyroid levels**, which is why follow-up testing is important.
What About Adding T3 to a T4 Medication?
There is another option that falls somewhere between T4-only therapy and desiccated thyroid: **prescribing T4 and T3 separately.**
For example:
Levothyroxine or Tirosint (T4) + liothyronine/Cytomel® (T3)
One potential advantage of this approach is that your physician can **control the amount of T4 and T3 independently** rather than relying on the fixed ratio found in desiccated thyroid.
Most patients can do very well on T4 alone. However, some people continue to experience symptoms despite appropriate T4 treatment and laboratory values. In selected patients, a carefully monitored trial of adding T3 may be considered.
Because T3 acts more quickly and has a shorter duration of action than T4, dosing needs to be individualized. Depending on the patient and dose, T3 may also be divided into more than one dose during the day.
Just like levothyroxine, **liothyronine products can contain different inactive ingredients depending upon the brand and manufacturer**, so patients with significant sensitivities may want their physician or pharmacist to review the specific product being prescribed.
Too much T3 can cause symptoms of thyroid excess—including **racing heart, palpitations, anxiety, tremor, sweating and difficulty sleeping**—and excessive thyroid hormone exposure over time can increase concerns about **abnormal heart rhythms and bone loss**.
T3 isn’t automatically “better” than T4. The goal is to determine whether a particular patient benefits from it and, if so, to find the **right balance of T4 and T3**.
So, Which Thyroid Medication Is Best?
There isn’t one answer.
For many people, **levothyroxine alone works beautifully**. Someone who has absorption difficulties, takes medications that affect stomach acid, or is sensitive to certain excipients may benefit from a simpler formulation such as **Tirosint**. Other patients feel their best using **Armour Thyroid or NP Thyroid**, while still others may benefit from individually prescribed **T4 plus T3**.
At Living Wellness Medical Center, our goal isn’t simply to choose a medication based on a single number on your lab report. We consider your laboratory results alongside **how you actually feel**, while making sure your thyroid replacement remains safe and appropriate.
If you have **celiac disease or significant sensitivities to gluten, lactose, dyes, corn or other medication ingredients**, please let your physician know. Formulations can change over time, and generic products can differ between manufacturers, so we may want to review the current ingredient list for your specific medication.
If your insurance company has recently stopped covering your current thyroid medication, **please don’t stop your medication or switch medications on your own.** Schedule a consult with your Living Wellness Physiica to discuss the options available to you.
When changing thyroid medications or adjusting a dose, we generally recommend **rechecking thyroid labs approximately six weeks later** so your physician can evaluate how your body is responding and make adjustments if necessary.
**The bottom line:** thyroid treatment isn’t necessarily one-size-fits-all. Whether your best fit is traditional T4, a more readily absorbed and simplified formulation such as Tirosint, desiccated thyroid, or carefully balanced T4/T3 therapy, our goal is the same: **healthy thyroid levels, safe treatment, and helping you feel your best.**
I specifically worded the gluten section around **current labeling** rather than making blanket claims, because excipient formulations can change and generics can differ by manufacturer. Synthroid’s current label, for example, states no ingredients are made from gluten-containing grains but does list lactose and various dyes depending on strength. ([DailyMed][2]) Armour’s current listed excipients include dextrose, microcrystalline cellulose and other tablet ingredients. ([DailyMed][3])
[1]: https://npthyroid.com/faq/?utm_source=chatgpt.com “Frequently Asked Questions | NP Thyroid® (thyroid tablets, USP)”
[2]: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=1e11ad30-1041-4520-10b0-8f9d30d30fcc&utm_source=chatgpt.com “DailyMed – SYNTHROID- levothyroxine sodium tablet”
[3]: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f5a1ce3b-9c62-48da-9ad1-5fe771ae8ccb&utm_source=chatgpt.com “DailyMed – ARMOUR THYROID- thyroid, porcine tablet”
