Levothyroxine

What Does Levothyroxine Do?

Levothyroxine is a synthetic form of thyroid hormone thyroxine, used to treat hypothyroidism, a condition where the thyroid gland doesn't produce sufficient thyroid hormones. 

How Does Levothyroxine Work?

Levothyroxine supplements low thyroid hormone levels in the body, crucial for growth, development and metabolic regulation. The synthetic hormone increases the body's natural thyroxine (T4) levels, converting to triiodothyronine (T3), the active thyroid hormone form, normalising metabolic functions and alleviating hypothyroidism symptoms. 

Effects are seen across body tissues, heart function, digestion, brain development, muscle control and bone maintenance. Its off-label uses include treatment of subclinical hypothyroidism and preventing thyroiditis recurrence.

Drug Type and Category of Levothyroxine

Levothyroxine is a synthetic thyroid hormone, and is classified as a thyroid hormone replacement.

It's also used to manage myxedema coma (a rare, life-threatening complication of severe, long-standing hypothyroidism) and in thyroid cancer patients post-thyroidectomy. 

What dosage of Levothyroxine should you be taking?

The recommended dosage for levothyroxine varies from 25 mcg to 200 mcg daily, dependent on age, weight, and severity of the condition. 

NHS Recommendations ¹

• Adults usually start with a dose between 50-100 micrograms taken once daily, which may be increased gradually over a few weeks to 100-200 micrograms once daily.
• Some people, such as those over 50 or with heart disease, may start on a lower dose.
• The dose is adjusted based on regular blood tests to monitor thyroid hormone levels and ensure the correct dose is reached. Once the correct dose is established, blood tests are usually done once a year to monitor levels.

What are the side-effects of Levothyroxine?

The most common side effects of Levothyroxine include increased appetite, weight loss, heat sensitivity, excessive sweating, headache, hyperactivity, nervousness, anxiety, irritability, mood swings, trouble sleeping, tiredness, tremors, muscle weakness, changes in menstrual periods, hair loss, diarrhoea, vomiting, and stomach cramps.

More serious but rare side effects include fast or irregular heartbeats, chest pain, fever, swollen glands, allergic reactions with symptoms like swelling of the face/throat and trouble breathing, and high blood sugar.

Drug Interactions

Levothyroxine is known to have significant interactions with several medications and supplements:

• Iron, calcium, and multivalent ions (found in antacids, vitamins, and supplements) can interfere with the absorption of levothyroxine, reducing its effectiveness. These should be taken at least 4 hours apart from levothyroxine. ²
• Proton pump inhibitors like omeprazole can increase serum thyroid stimulating hormone (TSH) levels, potentially reducing the efficacy of levothyroxine. ⁵
• Statins like atorvastatin can decrease serum TSH levels, potentially leading to overtreatment with levothyroxine.
• TSH should be monitored when these drugs are co-administered. ⁵
• Oestrogen can increase serum TSH, requiring dose adjustments of levothyroxine. ⁵ 
• Drugs like sucralfate, bile acid sequestrants, and phosphate binders can also interfere with levothyroxine absorption and should be separated by at least 4 hours. ⁶

In general, it is important to take levothyroxine on an empty stomach, 30-60 minutes before the first meal of the day, and to avoid taking it at the same time as other medications or supplements that can interact. ³ Careful monitoring of TSH levels is required when starting, stopping, or changing any medications taken concurrently with levothyroxine.

Natural Alternatives to Levothyroxine

Natural alternatives to Levothyroxine can include iodine, integral for T4 production, and selenium, a trace element that supports thyroid hormone metabolism. Zinc is also beneficial for thyroid health. Ashwagandha can boost thyroid function in subclinical hypothyroidism. ⁹ Fish oil provides omega-3 fatty acids, improving thyroid function, while L-Tyrosine can help the production of thyroid hormones combined with iodine. ¹⁰ 

Selenium is a mineral that plays a role in thyroid function. Studies have found that low selenium levels may be associated with thyroid diseases, so maintaining adequate selenium levels through foods like tuna, turkey, Brazil nuts, and grass-fed beef may help support thyroid health. ^5,6,7

Low vitamin B12 levels have been linked to thyroid problems, including hypothyroidism and autoimmune thyroid diseases. Vitamin B12 supplements may help support a healthy thyroid gland. ^5,6

Low vitamin D levels are associated with thyroid diseases. Some studies have found that vitamin D supplementation may help manage thyroid problems in people treated with levothyroxine, though more research is needed. ¹¹

There is anecdotal evidence that essential oils like lavender, peppermint, and rosemary may help manage hypothyroidism symptoms, though clinical trials have not proven these claims. ⁶

Natural desiccated thyroid extract from animal sources, such as Armour Thyroid, contains a natural form of thyroid hormone and may be an alternative to levothyroxine for some people. ^6,7

Interesting facts about Levothyroxine

There are several myths about Levothyroxine - let’s bust some of them!

Myth: Levothyroxine is unsafe during pregnancy.

Fact: Properly managed thyroid hormone levels are crucial during pregnancy for both maternal and foetal health. In fact, untreated hypothyroidism during pregnancy can lead to complications. Levothyroxine is considered safe and essential for managing hypothyroidism in pregnant women, with dosage adjustments often required under medical supervision. ¹²

Myth: Natural thyroid hormone supplements are safer and more effective than levothyroxine.

Fact: Levothyroxine is a synthetic form of thyroid hormone that mimics the body's natural thyroxine (T4). It is precisely dosed and standardised, making it a reliable treatment for hypothyroidism. Natural thyroid hormone supplements, derived from animal thyroid glands (like desiccated thyroid extract), can vary in potency and may not provide consistent hormone levels. They are also less commonly prescribed due to these inconsistencies and the availability of standardised levothyroxine. ¹³

 

Fact: Levothyroxine was the fifth most commonly prescribed drug in the UK in 2023-2024. 

Controversies around Levothyroxine

There are many controversies around levothyroxine. Some people argue that taking a drug to change thyroid hormone levels is unnatural, and could be done through lifestyle changes. This is often due to side-effects and allergic reactions. 

There are also concerns around the quality of the drug, storage and processing, with different manufacturers having been sued for poor quality levothyroxine drugs causing significant side-effects. In 2017, the manufacturer of Euthyrox (a brand of levothyroxine) reformulated the medication to improve its stability. However, this change led to widespread patient reports of adverse effects and symptom return, causing significant controversy and legal action in several countries. In addition, the FDA has investigated and sometimes issued recalls for specific batches of levothyroxine that did not meet potency standards.

Levothyroxine also requires precise dosing. Just small changes in dosage can lead to significant changes in thyroid hormone levels. Managing this precision is challenging, especially given the variability in absorption between different formulations. This requires regular blood monitoring which is not always possible, and patients can be left taking the same dosage for years. 

Disclaimer:

This article is generated for informational purposes only. It was created in June 2024. Medications and medical guidance can change over time. Therefore, it is essential to consult with your general practitioner or healthcare provider before making any decisions regarding medications or treatment plans. Your GP can provide personalised advice based on your specific health needs and conditions.

References

1. https://www.nhs.uk/medicines/levothyroxine/
2. https://www.drugs.com/drug-interactions/levothyroxine.html
3. https://go.drugbank.com/drugs/DB00451
4. https://pubmed.ncbi.nlm.nih.gov/25040647/
5. https://www.drugs.com/medical-answers/take-other-medications-levothyroxine-3562434/
6. https://www.healthline.com/health/hypothyroidism/five-natural-remedies-for-hypothyroidism
7. https://www.linkedin.com/pulse/natural-thyroid-medication-alternatives-synthroid-thrivelabco
8. https://renuerx.com/general-health/4-natural-remedies-for-hypothyroidism-medication-alternatives/
9. https://www.medicalnewstoday.com/articles/remedies-for-hypothyroidism
10. https://nccih.nih.gov/health/ashwagandha
11. https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/
12. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
13. https://www.thyroid.org/thyroid-hormone-treatment/