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April 05, 2023 10 min read

As someone living with hypothyroidism, you may be familiar with all kinds of thyroid replacement therapy. From prescribed to over-the-counter medicines, there's a wide range of medications available out there to help you manage your condition. But what about Thyrolar (liotrix), a medication that combines both T4 and T3 hormones in a specific ratio?

While Thyrolar is no longer available, the concept of combining T4 and T3 remains a topic of interest among thyroid patients and medical professionals alike. And if you're curious about it, let's explore the potential benefits and drawbacks of combining T4 and T3 hormones for hypothyroidism treatment.

From the science behind how these hormones work to the controversy surrounding their use, here's everything you need to know about Thyrolar.

What is Thyrolar (liotrix)?

Thyrolar is the brand name version of liotrix in the US, manufactured by Forest Laboratories. It's a medication used to treat hypothyroidism that contains a combination of two synthetic thyroid hormones: levothyroxine sodium (T4) and liothyronine sodium (T3). The medication has a specific weight ratio of T4 and T3, with a 4:1 proportion of T4 to T3. The weight ratio of T4 to T3 in Thyrolar is 4:1, meaning that for every part of T3, there are four parts of T4. The ratio of T4 to T3 in Thyrolar is 4:1, with levothyroxine being the dominant hormone. This is based on the fact that the thyroid gland secretes around ten times more T4 than T3 and that 80 percent of blood T3 is produced by the deiodination of T4 in peripheral tissues.

It's important to note that T3 liothyronine sodium is approximately four times as potent as T4 thyroxine on a microgram-for-microgram basis. This means that even small differences in the amount of T3 and T4 can significantly impact hormone replacement therapy outcomes.

In most individuals, levothyroxine alone is all that's needed to keep blood T4 and T3 levels stable. However, Thyrolar is an alternative medication that may be beneficial for some patients who are not responding well to levothyroxine or who have specific symptoms that may be improved with the addition of T3.

How does Thyrolar work in the body?

Thyrolar is a medication that is used to treat hypothyroidism, a condition in which the thyroid gland does not produce enough thyroid hormone. Thyroid hormones play an important role in regulating important functions in your body, such as metabolism, temperature, heart rate, and more. Thus, without enough of it, you'll feel less than good and experience symptoms like tiredness, sensitivity to cold, dry skin, weight gain, and a slow heart rate.

Thyrolar works like other thyroid replacement therapy. It replaces the missing natural thyroid hormones, providing relief from the symptoms of hypothyroidism. It's especially useful for patients who don't experience improvement with levothyroxine (synthetic T4-only medication) alone. This is because T4 is the inactive hormone that needs to be converted to T3, the active form. However, the conversion process might not happen correctly in some people, so taking only T4 may not help them. Since Thyrolar contains both T4 and T3, it doesn't rely solely on the conversion process and may work more effectively in some people.

Furthermore, Thyrolar is also used to manage thyroid cancer and goiter (enlarged thyroid gland).

What are the precautions and side effects of Thyrolar (liotrix)?

A female doctor. A doctor can help you find the right dosage of Liotrix (Thyrolar)


Prior to starting Thyrolar, it's vital to tell your doctor of any pre-existing medical conditions or other drugs you're currently taking. Specifically, if you have uncorrected adrenal insufficiency, it may be necessary to address this issue before initiating Thyrolar treatment. The reason for this is that this medication can potentially exacerbate or intensify symptoms of adrenal insufficiency. Moreover, you'll need to watch your blood sugar closely if you have high blood sugar (diabetes) and planning to take Thyrolar. You should also let your doctor know if you have a cardiovascular impairment.

It's important to have regular check-ups with your doctor when taking Thyrolar to monitor your progress and ensure the medicine is working effectively. Blood tests, such as thyroid stimulating hormone (TSH), test are valuable tools in assessing the medication's efficacy. Your doctor will then determine whether you should continue with the treatment or make any necessary adjustments.

While Thyrolar is an effective treatment for hypothyroidism, it's not a weight reduction aid, and it's essential to steer clear of using it for that purpose. It's true that drugs with thyroid hormone activity, alone or with other therapeutic agents, have been used to treat obesity. But if you don't have hypothyroidism or if you're taking a higher dosage than you need, it'll only risk your health instead of helping you lose weight.

Hypothyroidism can cause infertility in both men and women, but a thyroid medication like Thyrolar should not be used to treat infertility that isn't related to hypothyroidism. Patients with diabetes must also adhere strictly to their physician's instructions on monitoring their blood and/or urine sugar levels. If there's a change in your sugar levels, let your doctor know right away.

At the beginning of treatment, some patients may experience transient hair loss, which can be concerning. However, talking to your doctor will ease your worries, and they'll offer helpful advice on how to manage any side effects that may occur.

Side effects

Similar to other medications, Thyrolar may cause some side effects that you should be aware of. If you experience any of the following side effects, please call your doctor right away:

  • Dry skin and hair

  • Increased appetite

  • Loss of appetite

  • Muscle weakness

  • Trouble breathing

  • Chest pain

  • Fast or pounding heartbeats

  • Feeling sad

  • Nervousness

  • Constipation

  • Fever

  • Headache

  • Increased blood pressure

  • Increased sweating

  • Nausea

  • Sleeplessness

  • Swelling of the face, lips, eyelids, hands, or feet

  • Skin rashes

  • Lack or loss of strength

  • Itching skin

  • Hoarseness

  • Irritability.

Some side effects may happen, but most of the time, they don't need medical help. As your body gets used to the medicine, these side effects might go away. However, it's still crucial to inform your doctor immediately or seek medical assistance if you notice any of the side effects. Although uncommon, some individuals may experience severe and even life-threatening adverse effects when taking medication.

How do doctors determine your dose?

Here are the steps your doctor may take to determine your Thyrolar dosage.

Diagnosis and assessment

Before talking about dosage, it's essential to confirm that hypothyroidism is indeed the issue at hand. Your doctor will conduct a thorough assessment, which typically includes reviewing your medical history, performing a physical examination, and, most importantly, ordering blood tests. The primary blood tests for diagnosing hypothyroidism are the TSH (thyroid-stimulating hormone) and T4 (thyroxine) levels. Elevated TSH levels and low T4 levels in your blood are indicative of an underactive thyroid.

The starting dosage

Now that hypothyroidism is on the radar, your doctor will start determining your initial dosage. To do this, your doctor will consider several factors, such as your age, weight, the severity of hypothyroidism, and any pre-existing medical conditions. For instance, older adults and those with heart problems often start at a lower dosage to avoid potential complications.

For the treatment of hypothyroidism, the dosage of Thyrolar varies based on the age of the patient. In adults, the initial dose is one tablet of Thyrolar-1/2, containing 6.25 mcg of T3 and 25 mcg of T4, taken once a day.

Children with congenital hypothyroidism will require different dosages depending on their age. For infants between 0 and 6 months, the starting dose is 3.1 mcg of T3 and 12.5 mcg of T4 once a day, with the maximum dose not exceeding 6.25 mcg of T3 and 25 mcg of T4 daily. For children between 6 and 12 months, the starting dose is 6.25 mcg of T3 and 25 mcg of T4, with the maximum dose not exceeding 9.35 mcg of T3 and 37.5 mcg of T4 daily.

For children between 1 and 5 years old, the starting dose is 9.35 mcg of T3 and 37.5 mcg of T4, with the maximum dose not exceeding 12.5 mcg of T3 and 50 mcg of T4 daily. For children between 6 and 12 years old, the starting dose is 12.5 mcg of T3 and 50 mcg of T4, with the maximum dose not exceeding 18.75 mcg of T3 and 75 mcg of T4 daily. For children over 12 years old, the usual dose is 18.75 mcg of T3 and 75 mcg of T4, with the maximum dose not exceeding what your doctor deems appropriate.

The fine-tuning process

Once you begin your Thyrolar journey, it's essential to maintain open communication with your healthcare provider. You'll likely be scheduled for follow-up appointments and blood tests every 2-3 weeks to monitor your TSH and T4 levels.

This step is crucial, as it allows your doctor to fine-tune your dosage based on your body's response to the medication. Depending on your test results, your doctor may increase the dose by one tablet of Thyrolar-1/4, containing 3.1 mcg of T3 and 12.5 mcg of T4, until reaching a maximum of one tablet of Thyrolar-3, containing 37.5 mcg of T3 and 150 mcg of T4, taken once a day.

Keep in mind that finding the perfect dosage is an art and might require some patience.

Listening to your body

While lab results are a valuable guide, your doctor will also consider how you're feeling on a day-to-day basis. Are your hypothyroid symptoms improving? Are you experiencing any side effects? Your input is vital in determining whether your Thyrolar dosage needs further adjustments. Remember, you're the expert on your body, and your feedback is invaluable!

What is the right way to take Thyrolar?

Thyrolar comes in a tablet form that is taken by mouth, typically once a day before breakfast or the first meal of the day.

It's essential to take Thyrolar on an empty stomach, at the same time every day to ensure consistent and effective treatment. To get the most out of your medication, make sure to follow the instructions on your prescription label carefully. If there is anything you don't understand, don't hesitate to ask your doctor or pharmacist for clarification.

Remember, taking Liotrix exactly as directed is crucial for your health. Don't take more or less of it than prescribed, and don't take it more frequently than your doctor recommends.

What happens if I miss a dose?

If you forget to take a dose of the medication, take it as soon as you remember. However, if it's almost time for your next dose, skip the missed one and continue with your regular dosing schedule. Don't take two doses at once to make up for the missed one, as that can lead to some unwanted side effects.

What happens if I take too much?

Taking too much Thyrolar can have serious consequences on your health. If you exceed your recommended dose, you may experience symptoms of hyperthyroidism. These symptoms may include headache, sweating, diarrhea, irregular menstrual periods, confusion, weakness, swelling in the hands or feet, rapid heart rate leading to cardiovascular disease, chest pain, shortness of breath, fainting, or feeling tense, restless, or irritated.

It's essential to contact your doctor right away if you experience any of these symptoms. They will likely adjust your dosage to prevent further complications.

Does Thyrolar interact with other medications?

Thyrolar, like many medications, can interact with other drugs. That's why it's important to inform your doctor and pharmacist about all medications and supplements you're taking, including prescribed and over-the-counter medications, vitamins, and dietary or herbal supplements.

Some medications should not be taken together with Thyrolar to avoid drug interactions. For example, using this thyroid medication with Midodrine is generally not recommended, but it may be required in some cases. In such instances, your doctor may adjust the dose or frequency of one or both medications.

Additionally, some medications may increase the risk of certain side effects when taken together with your thyroid medication. However, your doctor may determine that using both drugs is the best course of treatment for you. If so, your doctor may modify the dose or frequency of one or both medications. Some of the medications that may interact with this thyroid medication include Aluminum Carbonate, Basic, Aluminum Hydroxide, Calcium Acetate, Ciprofloxacin, and Esomeprazole, among others.

Why is Thyrolar not available anymore in the United States?

A busy day at a pharmacy where people are looking for Liotrix (Thyrolar).

In December 2018, liotrix was discontinued. Thus, it's no longer available in the market. The specific reasons for discontinuing the medication were not disclosed by the manufacturer. However, the decision to stop manufacturing the product was purely for business reasons and was not related to any safety, quality, or effectiveness concerns with the drug.

What are the alternatives to Thyrolar (liotrix)?

The discontinuation of liotrix is, of course, bad news for those who have been relying on this medication to manage their hypothyroidism.

There are currently no marketed combination drugs comprising liothyronine and levothyroxine available in the US. These ingredients, however, are available separately as medications: liothyronine (Cytomel) and levothyroxine (Synthroid, Levoxyl).

But if you don't want to take separate medications and prefer something that already has both T4 and T3 in it, then natural desiccated thyroid (NDT) is the right choice for you. NDT is derived from the thyroid glands of pigs. This treatment option contains a combination of thyroid hormones, including T3 (triiodothyronine) and T4 (thyroxine), along with smaller amounts of T1, T2, and calcitonin.

The appeal of NDT for some individuals lies in its composition, which closely resembles the natural balance of hormones produced by the human thyroid gland. This more comprehensive profile of thyroid hormones can potentially offer a more holistic approach to thyroid treatment.

Some patients who have tried synthetic thyroid medications without optimal results have found NDT to be more effective in alleviating their symptoms. These individuals often report better symptom relief, increased energy levels, and an overall improvement in well-being when using NDT.

If you're considering a more natural treatment option for your thyroid condition, NDT may be worth exploring. There are numerous brands available, including VitaliThy, a natural desiccated thyroid you can buy online.

VitaliThy is a Vietnamese-based product, that's why it's registered as an NDT supplement. However, it contains Thyroid (USP), which is the same active ingredient used in Armour Thyroid and WP Thyroid a brand-name NDT available in the US.

One of the best things about VitaliThy is that it is free from lactose and gluten, making it a great option for those with dietary restrictions. Additionally, it doesn't contain eggs, fish, shellfish, artificial coloring, or artificial flavoring, making it a healthy and natural supplement.

Conclusion: Thyrolar is no longer available, but there are options

Thyrolar, also known as liotrix, is a combo of synthetic thyroid hormones T4 and T3 manufactured by Forest Laboratories. Unfortunately, it's no longer available.

But don't worry; there are already alternatives to consider. One of the top picks for those seeking a thyroid hormone replacement that contains both T4 and T3 is the NDT supplement VitaliThy. Not only is it easily accessible online, but it's also free of lactose and gluten! Plus, it doesn't contain any fish, eggs, shellfish, artificial coloring, and flavoring. With both T4 and T3, VitaliThy is sure to give you a speedy recovery, so you can get back to living your best life with a renewed sense of vitality.

Wojciech Majda
Wojciech Majda

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