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Metformin, Hashimoto’s, and Hypothyroidism

A look at how the type 2 diabetes drug metformin works for Hashimoto’s and hypothyroidism.
Metformin, Hashimoto’s, and Hypothyroidism
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Metformin is a commonly prescribed medication for those with type 2 diabetes. However, in recent years, it has gained attention for its potential benefits for individuals with Hashimoto’s disease and hypothyroidism. Recent research has sparked interest and questions among patients and healthcare professionals alike. This article will explore the relationship between metformin, Hashimoto’s disease, and hypothyroidism.

What is metformin, and what does it do?

Metformin is an FDA-approved medication used to treat high blood sugar levels caused by type 2 diabetes. It belongs to a class of drugs called biguanides, which work by decreasing the production of glucose in the liver and increasing the sensitivity of muscle cells to insulin, a hormone produced by the pancreas. Metformin works by reducing the amount of glucose (sugar) produced by the liver and absorbed from the intestines and improving the body’s response and sensitivity to insulin. It does this by activating an enzyme called AMP-activated protein kinase (AMPK), which is crucial in regulating glucose metabolism.

Metformin is available in various forms, including tablets, extended-release tablets, suspensions, and solutions. Metformin is most commonly sold under the brand names Glucophage, Glumetza, and Fortamet. It is also available in combination drugs that include other diabetes medications such as sitagliptin (Janumet), empagliflozin (Synjardy), or dapagliflozin (Xigduo XR). These combination drugs are often prescribed to individuals who require multiple medications to manage their diabetes effectively.

Metformin is the most commonly prescribed medication for type 2 diabetes and has been in use for the past 70 years. In addition to being prescribed for type 2 diabetes, it is sometimes used for people with polycystic ovary syndrome (PCOS), as it can lower insulin and blood sugar levels and stimulate ovulation.

Metformin is usually prescribed along with a proper diet and exercise program to help effectively control blood sugar levels and prevent further complications. It is considered a first-line treatment for type 2 diabetes by the American Diabetes Association.

What are other health benefits of metformin?

Metformin not only helps to control blood sugar levels but also offers several additional health benefits. One significant health benefit of metformin is its potential for weight loss. It helps to decrease appetite and promotes a feeling of fullness, leading to weight reduction in some individuals. To learn more, you may want to read an article on the Paloma blog: Does Metformin Cause Weight Loss With Hypothyroidism?

Metformin’s positive effects on insulin sensitivity can improve lipid profiles, cholesterol, and triglyceride levels and reduce the risk of cardiovascular diseases.

Metformin has also been found to have anti-inflammatory properties, which can benefit overall health, as well as various conditions like polycystic ovary syndrome (PCOS) and non-alcoholic fatty liver disease.

Metformin’s ability to lower blood pressure and reduce the risk of certain cancers, such as colon and breast cancer, has also been observed in some research studies.

Metformin also modifies the gut microbiome and impacts the gut-brain axis, a communication network between the gut and the brain, including the neural, hormonal, immune, and metabolic networks, as well as the hypothalamic–pituitary–adrenal (HPA) axis.

Overall, metformin’s health benefits extend beyond its primary role in managing diabetes, making it a valuable medication for treating various health conditions.

Later in this article, we’ll also discuss research showing that metformin may have potential benefits for individuals with autoimmune diseases like Hashimoto’s thyroiditis and hypothyroidism.

What are the side effects of metformin?

While metformin is generally well-tolerated and considered safe for most individuals, it can cause certain side effects in some cases. Common side effects of metformin include gastrointestinal issues such as indigestion, abdominal pain, nausea, or diarrhea. Some people may also experience headaches, dizziness, or a metallic taste in their mouth. These side effects usually occur at the beginning of the treatment and can be minimized by taking the medication with food.

Another potential side effect of metformin is hypoglycemia or low blood sugar levels. Hypoglycemia is more likely to occur in individuals who take the medication along with other blood sugar-lowering drugs or those who skip meals. Symptoms of hypoglycemia include shakiness, dizziness, sweating, confusion, and in severe cases, loss of consciousness. It is crucial to carefully monitor blood sugar levels while taking metformin and take necessary precautions to prevent hypoglycemia.

In rare cases, metformin can cause more severe side effects. One of the most concerning potential side effects is lactic acidosis, a rare but potentially life-threatening condition. Lactic acidosis occurs when there is a buildup of lactic acid in the blood, which can happen if the kidneys are not functioning properly. Symptoms of lactic acidosis include weakness, muscle pain, difficulty breathing, nausea, vomiting, abdominal pain, and an irregular heartbeat. If you experience these symptoms while taking metformin, it is crucial to seek medical attention immediately. In severe cases, lactic acidosis can even lead to coma or even death, so it is vitally important to avoid or limit alcohol consumption while taking metformin to minimize the risk of lactic acidosis.

Other less common side effects of metformin include vitamin B12 deficiency, which can lead to anemia and nerve damage, and a rare but serious condition known as metabolic acidosis. Metabolic acidosis occurs when there is an imbalance of acid and base in the body, leading to symptoms such as rapid breathing, confusion, and fatigue. It is essential to discuss any symptoms or concerns with your healthcare provider so that they can monitor your response to the medication and make necessary adjustments if needed.

It is important to note that, generally, side effects with the use of metformin are rare and most people tolerate it well. Overall, it’s estimated that around 1 in 4 people experience some side effects, but in most patients, side effects diminish within 1 to 2 weeks. About 1 in 20 people treated with metformin experience persistent and severe gastrointestinal issues that can affect their quality of life and cause them to discontinue the medication.

Also, you should be aware that some medications may interact with metformin. These include drugs that affect the kidneys, such as diuretics, and certain medications for heart conditions, such as beta-blockers or calcium channel blockers. Additionally, certain antibiotics, such as trimethoprim, can increase the risk of lactic acidosis when combined with metformin. It is essential to inform your healthcare provider about all your medications, including over-the-counter drugs and supplements, to ensure no potential interactions with metformin.

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Metformin, Hashimoto’s, and hypothyroidism

Hashimoto’s thyroiditis is an autoimmune condition that mistakenly causes the body’s immune system to attack the thyroid gland. A Hashimoto’s attack leads to inflammation and gradual destruction of the thyroid tissue, eventually resulting in an underactive thyroid or hypothyroidism. Symptoms of hypothyroidism can include fatigue, weight gain, hair loss, and depression.

In recent years, researchers have noticed a connection between Hashimoto’s thyroiditis and insulin resistance, a condition in which the body’s cells become less responsive to the effects of insulin. Insulin resistance is a hallmark of type 2 diabetes and can also occur in prediabetics.

Metformin works by decreasing glucose production in the liver and improving insulin sensitivity in the body. It helps the body use insulin more effectively, benefiting individuals with insulin resistance, type 2 diabetes, and potentially, those with Hashimoto’s thyroiditis.

Several studies have examined the effects of metformin on thyroid function in individuals with hypothyroidism. These studies have shown promising results, suggesting that metformin may help increase thyroid hormone absorption and the metabolism of thyroid hormones, helping improve thyroid hormone levels and reduce symptoms of hypothyroidism in some individuals.

Some studies suggest that metformin use may have an influence on thyroid hormone levels. Research conducted on individuals with diabetes has shown that metformin may alter thyroid hormone secretion and function. One possible mechanism is that metformin may reduce the activity of an enzyme called deiodinase, which is responsible for converting T4 into its active form, T3. Metformin may reduce T3 levels by inhibiting this enzyme, potentially resulting in certain thyroid-related issues.

One study published in the International Journal of Endocrinology showed that metformin treatment in women with hypothyroidism resulted in improved thyroid hormone levels, reduced TSH (thyroid-stimulating hormone) levels, and improved ovulation. Another study showed that metformin treatment in individuals with insulin resistance and Hashimoto’s thyroiditis improved thyroid hormone levels and reduced TSH levels. These findings indicate that metformin may positively impact thyroid function in some cases.

Experts also believe that metformin may be able to change the affinity and/or quantity of thyroid hormone receptors and activate those receptors, enhancing the effects of thyroid hormones on the pituitary.

Research has shown that metformin can significantly lower TSH levels in hypothyroid individuals, including those who are untreated.

Metformin also seems to positively affect different autoimmune conditions, including Hashimoto’s. Research shows that metformin can reduce Thyroglobulin and Thyroid Peroxidase antibodies (TgAb and TPOAb) and the inflammation they cause. This reduction in antibody levels suggests a potential modulation of the immune response.

One study of patients with Hashimoto’s thyroiditis found that metformin had a therapeutic effect primarily by reducing thyroglobulin antibodies (TgAb), inflammation in thyroid tissue, and lymphocyte infiltration. Lymphocytes are immune cells that play a role in the autoimmune response seen in Hashimoto’s thyroiditis. By reducing lymphocyte infiltration, metformin may help to alleviate the inflammation and damage to the thyroid gland.

Interestingly, when you combine metformin with vitamin D, the effect is even more potent in reducing the thyroid antibody levels, improving insulin sensitivity, and balancing thyroid hormones, including T3. These findings suggest that combining metformin and vitamin D can benefit individuals with Hashimoto’s thyroiditis.

Research has also found that metformin may modulate Th17 cells. These cells are a subset of T helper cells involved in autoimmune responses. By modulating Th17 cells, metformin may help to balance the immune response and reduce inflammation in the thyroid gland.

Finally, research suggests that metformin can positively impact your intestinal flora and bacterial balance. The gut microbiota has been implicated in autoimmune diseases, and modulating the gut microbiota may help improve your immune response in Hashimoto’s thyroiditis and immune function in general.

What dosage of metformin is recommended?

The standard dosage of metformin for treating type 2 diabetes is 500 mg twice daily or 850 mg once daily. There’s no clear consensus on the recommended dosage of metformin for patients with Hashimoto’s thyroiditis or hypothyroidism. However, here are some findings from research studies:

Overall, the recommended dosage of metformin for patients with Hashimoto’s thyroiditis and/or hypothyroidism varies depending on the patient’s condition and other factors. It is essential to consult with a healthcare provider to determine the appropriate metformin dosage for each patient.

Remember, however, that metformin is not a standalone treatment for Hashimoto’s thyroiditis or hypothyroidism. Another important consideration is that if you’re hypothyroid and taking metformin, you may experience changes in your thyroid hormone levels. Anyone evaluating your thyroid blood test results should be made aware that you are taking metformin so they can accurately interpret your test results. 

Other guidelines when taking metformin

If you are prescribed metformin, take the medication exactly as your healthcare provider prescribes. Sticking to your prescribed medication regimen is crucial for effective treatment. It is usually taken with meals to minimize gastrointestinal side effects. Do not skip doses or alter the dosage without consulting your healthcare provider.

It’s also important to drink plenty of fluids while taking metformin. Adequate hydration helps prevent dehydration and supports kidney function. Consult with your healthcare provider regarding the recommended daily water intake for you.

Finally, regularly monitor your blood sugar levels while taking metformin. This will help you track your progress and determine if any adjustments in medication or lifestyle are necessary.

A note from Paloma

Remember that not all individuals with Hashimoto’s thyroiditis or hypothyroidism will benefit from metformin treatment. Each person’s response to the medication may vary, and it should always be prescribed and managed by a healthcare professional.

Additionally, it is crucial to address the underlying causes of Hashimoto’s thyroiditis and hypothyroidism, such as nutrient deficiencies, gut health issues, and chronic inflammation. Metformin should be considered a potential adjunct to these treatments rather than a standalone solution.

The best way to monitor your Hashimoto’s and hypothyroidism is with regular testing. Paloma’s convenient at-home testing kit makes diagnostic tests for TPO antibodies easy and fast. All it requires is a finger prick blood sample to be mailed in. The test evaluates your thyroid stimulating hormone (TSH), free thyroxine (free T4), and free triiodothyronine (free T3) levels – as well as thyroid peroxidase antibodies (TPOAb) – giving you a complete picture of your thyroid function.

If you have hypothyroidism or Hashimoto’s thyroiditis and are interested in exploring the potential benefits of metformin, it is important to discuss this with your healthcare provider. They can evaluate your individual case, consider the risks and benefits, and determine if metformin may be a suitable addition to your treatment plan.

You can book an appointment with one of Paloma’s experienced thyroid health care providers, who will help you discuss a treatment plan for your hypothyroidism, along with lifestyle recommendations to help ensure relief of your hypothyroid symptoms, optimal thyroid function, and overall wellness.

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Vedrana Högqvist Tabor, Ph.D., contributed to this article.


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Mary Shomon

Patient Advocate

Mary Shomon is an internationally-recognized writer, award-winning patient advocate, health coach, and activist, and the New York Times bestselling author of 15 books on health and wellness, including the Thyroid Diet Revolution and Living Well With Hypothyroidism. On social media, Mary empowers and informs a community of more than a quarter million patients who have thyroid and hormonal health challenges.

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