Mounjaro and levothyroxine

Can you take Mounjaro and levothyroxine at the same time? If you struggle with your weight and your thyroid gland is underactive, you may want to take levothyroxine with Mounjaro. While the drugs are generally safe to take together, it is important to understand how these drugs interact with each other to make sure you are not doing more harm than good for your body. This blog will tell you everything you need to know about Mounjaro and levothyroxine.

Key takeaways

• Mounjaro and levothyroxine can generally be taken together:
  There are no direct interactions between Mounjaro (tirzepatide) and levothyroxine, so it is usually safe to use both medications at the same time for people with hypothyroidism who are also managing their weight.
• Close monitoring of thyroid levels is important:
  While no direct interaction exists, GLP-1 medications like Mounjaro can affect thyroid hormone needs—possibly by altering absorption or due to weight loss. Regular thyroid function tests and possible dose adjustments of levothyroxine may be necessary.
• Weight loss with Mounjaro may reduce levothyroxine needs:
  Significant weight loss can lower the requirement for thyroid hormone replacement, so your levothyroxine dose might need to be adjusted as you lose weight.
• How you take levothyroxine matters:
  Levothyroxine should be taken on an empty stomach, ideally 30–60 minutes before breakfast or several hours after eating, and certain foods (like soy, papaya, grapefruit, and coffee) can interfere with its absorption.
• Always personalise your treatment and consult your healthcare provider:
  Medication responses vary from person to person. If you are taking both Mounjaro and levothyroxine, regular check-ins with your healthcare provider or pharmacist are essential to ensure your treatment stays safe and effective.

Thyroid levels and body weight

The hormones in our thyroid are responsible for how well our metabolism works. As a result, there is a general perception that when our levels are low, we tend to gain weight.

So many times, we blame our weight gain on our sluggish metabolism; this blog will shine some light on the matter as well as look at the interaction of the medications mentioned above.

The role of thyroid hormones in metabolism and body weight

Thyroid hormones are essential for controlling your body’s development, growth and energy use. Let’s see how they do this:

Thyroid hormones and metabolism

Thyroid hormones manage your body’s basal metabolic rate (BMR)—the amount of energy your body needs at rest.

This is directly correlated to the amount of calories you burn daily, without any physical activity [1]. So, if your metabolism is falling behind, then sadly, you will probably to gain a bit of weight.

Thyroid hormones and temperature regulation

Thyroid hormones also control thermogenesis, which is the process your body undergoes to generate heat to maintain optimal body temperature [2].

So, if everyone around you is wearing shorts and t-shirts while you are wrapped up in thick jumpers, it may be time to check your thyroid levels.

Thyroid hormones glucose and fat metabolism

Thyroid hormones are essential for lipid metabolism, which includes breaking down fats for energy and controlling cholesterol levels [3].

These hormones also play a role in glucose metabolism and ensuring blood sugar levels are stable [4].

Also, thyroid hormones can determine how efficiently your body burns fat as fuel by regulating fat oxidation [5].

So, now that you have a better understanding of why people generally tend to gain weight when these vital hormones are low, let’s dive deeper into the science.

Euthyroid a balance

Eu what, mate? Euthyroid is a state in which the thyroid glands are functioning well and producing the current amount of thyroid hormones (T3 and T4, to be exact).  The hormones are key to maintaining a healthy metabolism.

In an euthyroid state, thyroid hormone levels are optimal, not too high (hyperthyroidism) and not too low (hypothyroidism). It’s the thyroid level that Goldilocks would say is just right.

This balance is essential for overall health, as thyroid hormones play a crucial role in regulatory functions such as energy production, metabolism, and body temperature regulation.

However, what happens when your hormones are out of balance and your body slips out of the euthyroid state? Or, to use the Goldilocks metaphor further, what happens when your porridge is too hot or cold or a bear is sitting in it?

Hyperthyroidism or excess thyroid hormone

When your thyroid produces too much of a hormone, it causes the body to be in a hypermetabolic state [6] :

• Weight loss: Your body burns uses energy faster than normal.
• Low cholesterol: Cholesterol levels drop and the body uses fats more efficiently.
• Increased fat breakdown: The fat stores in the body breaks down (lipolysis).
• Higher glucose production: Your liver increases glucose production, which is needed for energy (gluconeogenesis).

I know what you are thinking, and stop it! Before you ask, the answer is NO!

You should NEVER EVER take levothyroxine for weight loss. It could create a thyroid storm, which can in fact be fatal, and if you don’t believe me, you can read the following case study:

Lethal thyroid storm after uncontrolled intake of liothyronine in order to lose weight [7].

Hypothyroidism (Too little thyroid hormone aka the porridge is too cold)

So what happens if you your porridge is too cold and your thyroid levels are low? When your thyroid hormone levels are low, your metabolism slows down, leading to [8]:

• Weight gain: Your body burns less energy and stores more bodyfat.
• Higher cholesterol: Fat processing will slow down thus increasing cholesterol levels.
• Reduced fat breakdown: The body struggles to use and breakdown stored fat.
• Lower glucose production: Your liver produces a less amount of glucose.

How thyroid hormones balance energy

Thyroid hormones can be seen as a thermostat for energy use, controlling the balance of energy storage and expenditure  [2]. Just as you don’t want expensive energy bills, you want your house to be energy-efficient. The cost of living crisis is no joke. You also want your hormone levels to be balanced to ensure maximum efficiency for your body.

What is levothyroxine?

OK, so, unfortunately,, you have been diagnosed with low thyroid levels; what do you do? Do you cry? Yes, but just a bit.  Do you live in a constant state of weariness and eventual weight gain?

Well, thanks to modern science, we can now replace our T4 thyroid hormones. Yes, there is also a T3, which is a bit controversial, so we will save that for another blog.  

What is T4?

Levothyroxine, or L-thyroxine for short, is a synthetic version of T4, a hormone produced in the thyroid gland.

This medication helps you manage your metabolism, body temperature, and energy levels in you have an underactive thyroid.

Taking levothyroxine daily, preferably on an empty stomach, helps replace the body’s natural T4 levels, maintaining a steady metabolism and energy level [9].

Mounjaro and levothyroxine

So now we should know that unlucky people who have hypothyroidism may have a harder time with weight management due to a slower metabolism. Research shows that those who underactive thyroids are at higher risk of developing obesity [10].

For some, adding a medication such  Mounjaro  to their levothyroxine treatment may help boost their weight loss results.

But can you or should you take Mounjaro with levothyroxine? Are there any potential unwanted interactions we should be aware of? Before we find out, let’s turn our attention to Mounjaro.

What is Mounjaro?

Mounjaro, the catchy brand name for tirzepatide, is a newly approved weekly injection for weight management.

Who can use Mounjaro?

In November 2023, the UK’s Medicines and Healthcare Products Regulatory Agency (or MHRA for short) licensed Mounjaro for use in adults with obesity (BMI of 30 or above) or those who are overweight (a BMI between 27 and 30) and have health conditions related to their weight [11].

On a side note, BMI may not be the best indicator for a healthy body; if you are a regular gym goer and pack a lot of muscle, you may get misdiagnosed as fat. Please don’t take it personally; BMI is trying its best.

How does Mounjaro work?

Mounjaro is an injectable medication that aids weight loss and controls blood sugar levels.

It mimics two hormones—GLP-1 and GIP—which regulate blood glucose levels and make you feel full and satisfied after meals [12].

How to take Mounjaro?

It’s a weekly injection, making it super convenient, and also it’s a subcutaneous injection, so it’s not that painful to administer [13].

Does Mounjaro cause weight loss?

Yes! Here is the evidence.

The Surmount 1 trial

This trial which was carried out over the course of 72 weeks, saw individuals lose up to 22.5% of their body weight when taking the Mounjaro 15mg injection [14].

The Surmount 4 trial

This trial dealt with weight loss in severely obese people, saw a massive 24.2% weight loss in those who took the Mounjaro 15mg injection [15].

What strengths of Mounjaro are available?

Mounjaro is offered in pre-filled injection pens with the following doses:Mounjaro 2.5mg,

• Mounjaro 2.5mg,
• Mounjaro 5mg,
• Mounjaro 7.5mg,
• Mounjaro 10mg,
• Mounjaro 12.5mg, and
• Mounjaro 15mg.

It is taken weekly as a subcutaneous injection, usually in the stomach or thigh or anywhere with a bit of fat.

The dosing schedule for Mounjaro

• Initial Phase: Begin with Mounjaro 2.5mg once a week for four weeks.
• Dose Increase: Increase dose to Mounjaro 5mg weekly after the initial phase.
• Further Adjustments: If your healthcare provider recommends, the dose can be increased in four-week intervals, up to Mounjaro15mg weekly.

This gradual escalation helps the body adjust to the drug and reduce the risk of side effects.

Clinical trials have shown that if side effects were to occur it would be during the adjustment period while the is body getting used to the drug  [14].

How does Mounjaro cause weight loss?

Mounjaro’s active ingredient, tirzepatide, works by supressing appetite, making  you feel full, reducing your hunger, and minimising food cravings [16]. This makes you eat less and lose weight naturally.

Mounjaro, the twincretin

What makes Mounjaro different from it’s competitors is that it’s the first medication to combine two gut hormones: GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) [12].  

These hormones also known as  “incretins” increase insulin release when the food that has been consumed makes it’s way to the gastrointestinal tract. These hormones enable better  appetite control and boosts your metabolism.

Because Mounjaro combines GLP-1 and GIP, it’s often called a “twincretin.” This double whammy not only controls your appetite and slows stomach emptying down but also enhances the weight-loss effects compared to if these hormones were working alone [12].

In short, Mounjaro’s allows you to eat less, stay satisfied, and lose more weight.

The following table highlights the benefits of the individual hormones, GLP-1 and GIP

Can you take Mounjaro with levothyroxine?

There are no interactions  between Mounjaro and levothyroxine.

Given that being in a hypothyroid state or having lower levels of thyroxine can encourage weight gain, it would make sense that taking Mounjaro can make you lose weight.

However, just because there is no listed interactions between Mounjaro and levothyroxine, it doesn’t mean that you should not take precautionary measures, as the following case study demonstrates.

A case study of increased thyroid levels after taking semaglutide

A study in the Journal of the American Pharmacists Association highlights the importance of closely monitoring hormone levels while taking Mounjaro or a GLP-1 receptor agonist, like Wegovy.

The case study of a 43-year-old woman who had her thyroid taken out and was taking levothyroxine to treat hypothyroidism. After starting for weekly GLP-1 injection, semaglutide, she experienced significant suppression in her thyroid-stimulating hormone (TSH). This change meant her levothyroxine dose to be cut down by 25% [17].

Does semaglutide decrease TSH levels?

The exact reason behind the  above patient’s fall in TSH levels we are not fully aware of, but this  may be due to:

• A direct effect of GLP-1 on TSH levels.
• Delayed stomach emptying caused by the medication, which alters levothyroxine absorption.
• Weight loss associated with GLP-1 use (a whopping 13 kg loss in this case), can reduce the need for thyroid hormone replacement.

Other case studies found a similar effect when combining TSH when GLP-1 receptor agonists were combined [18].

Why should you be careful before taking Mounjaro with levothyroxine

The case study above demonstrated that GLP-1-containing medications, like Mounjaro,  can interfere with other treatments, especially those which require precise dosing, such as levothyroxine.

So if you are taking levothyroxine to treat hypothyroidism  can you still take Mounjaro? Yes, you can take the Mounjaro with levothyroxine, but you will need to have your thyroid levels checked more regularly.

Mounjaro and levothyroxine summary

This case highlights the importance in personalised care, no two people are the same hence everything you take should be tailored to your individual needs. Weight loss or changes in medication absorption could cause the need to make adjustments with your prescriptions so if you are ever unsure do not hesitate to contact us at courier pharmacy if you unsure about Mounjaro, levothyroxine or any other medication we are always happy to help.

If you have any burning questions about Mounjaro and other potential interactions, you can read our blogs, such as, “Can you drink alcohol while taking Mounjaro?” and “Mounjaro side effects”.

How food and timing affect thyroid medication

Not only medicines can interact with levothyroxine, certain foods and eve the timing of your meals can impact how your body absorbs levothyroxine.

Certain foods and drinks can interfere with how well your body can absorb levothyroxine. Substances such as soy products [19],   [20] , papaya [21], grapefruit [22], and even coffee [23] have been shown to interfere with absorption, meaning the medication may not work as effectively as it should.

How to take levothyroxine?

It is best to take levothyroxine on an empty stomach to enhance absorption. It is best practice is to take your thyroid medication as a single dose daily. Ideally, taken30–60 minutes before breakfast or several hours after eating.

Stick to a routine, take it at the same time every day in the same way (e.g., with or without food) and avoid foods that interfere with absorption close to your dosing time.

These tips will help stabilise your thyroid hormone levels and ensure optimal conditions for the medication to work.

Is Mounjaro right for you?

Get a FREE telephone consultation with one of our pharmacists today!

Call me about Mounjaro

This content was created by our Medical Mojo team to provide general information and is not a substitute for professional medical advice. For personalised recommendations about your health, always consult with your doctor or healthcare provider.

References

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14. ClinicalTrials.gov, 2024. A randomized, double-blind, placebo-controlled, multicenter study to evaluate the efficacy and safety of ubiquinol in patients with statin-associated muscle symptoms (SAMS).
15. Aronne, L.J., Sattar, N., Horn, D.B., Bays, H.E., Wharton, S., Lin, W.Y., Ahmad, N.N., Zhang, S., Liao, R., Bunck, M.C. and Jouravskaya, I., 2024. Continued treatment with tirzepatide for maintenance of weight reduction in adults with obesity: the SURMOUNT-4 randomized clinical trial. Jama, 331(1), pp.38-48.
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• Deiana, L., Marini, S. and Mariotti, S., 2012. Ingestion of large amounts of papaya fruit and impaired effectiveness of levothyroxine therapy. Endocrine Practice, 18(1), p.98.
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