Does methimazole cause weight gain? (+3 tips)

In this article, we will discuss whether methimazole causes weight gain. We will share the mechanism through which methimazole causes weight gain, evidence from research, some tips to manage weight gain, and other relevant information.

Does methimazole cause weight gain?

Yes, methimazole causes weight gain in patients. Research suggests that patients show weight gain following treatment with methimazole within 2 months. This may peak till 6 months while taking the drug, and then gradually subside (1).

Methimazole is an oral medication that has been approved by the FDA for the treatment of hyperthyroidism. It is a thionamide drug, that is essential in cases that cannot be treated by surgery or by the use of radioactive iodine (2).

Methimazole can also be used to treat hyperthyroidism caused by medications. Medications like Celexa can influence thyroid function.

Methimazole works by inhibiting the production of an enzyme that helps synthesize the major thyroid hormones, especially thyroxine (T4) and triiodothyronine (T3) (2).

When this enzyme is inhibited, it leads to decreasing the over-production of the hormones, restoring normal thyroid function (2).

How does methimazole cause weight gain?

Thyroid medications are not meant to target issues of weight gain or loss but rather address the abnormal activity of the thyroid gland. However, most of the medications like methimazole that treat hyperthyroidism cause weight gain (1).

Methimazole has been reported to cause weight gain in the initial stages of therapy (1). Overactivity in the thyroid gland leads to weight loss as the increased production of thyroid hormones accelerates the catabolic functions in the body.

This leads to depletion of the mass of the body, both of the fat and the muscle. This is one of the primary symptoms of hyperthyroidism and despite increased appetite and over-eating, there is severe weight loss. (3)

When treatment with methimazole is started, the production of the enzyme thyroperoxidase is stopped which in turn stops the overproduction of thyroid hormones. (2)

Hence, the weight that was being lost starts to rapidly regain. However, it is still uncertain if the weight gained back is balanced in between both the regain of fat and muscle mass. (1)

Is the weight gained through methimazole healthy?

Despite much research, there is conflicting data about the balance and healthiness of the weight gain associated with antithyroid medications like methimazole.

This is because it is unclear if the changes that arise in a patient’s body composition are only of lean mass, fat mass, or both (4).

The reason for the contrasting results of studies is that there is a lot of variability in the body composition of patients.

There is also a differential effect of varied treatments, and it is also affected by many factors such as the gender, lifestyle, and severity of the condition in a particular patient. (5)

What does research suggest?

Various studies suggest that there is indeed a weight gain caused by the use of methimazole in patients.

In one study, six women who were newly diagnosed with Grave’s disease were given a treatment regimen of methimazole for 52 weeks and were observed for weight gain (1).

After the assigned period, the results showed an increase in weight gradually for the first 8 weeks, then it reached a high from week 8 till 24 and then decreased from week 24 onwards until the end of the 52 weeks. (1)

This is the reason that clinicians need to adequately counsel the patients about the subsequent weight that might be gained due to taking methimazole.

If the patient does not know, the rapid weight changes might stress them out and render them incapable of managing both the gain and loss of weight properly during the treatment of the disease. (5)

What other factors contribute to methimazole-induced weight gain?

Other possible factors exacerbate the increase in weight while the patient is taking methimazole, which includes the following:

What are some tips for weight management?

Even though the weight gain induced by antithyroid drugs cannot be stopped, it can be managed well by incorporating some lifestyle modifications. These are discussed below.

Regular exercise: 

Physical activity has been shown to have good effects on health regardless of the state of the thyroid. It also enhances the patient’s mental well-being and empowers them to stay on a progressive track when it comes to staying healthy.

The imbalance of weight loss caused by hyperthyroidism and the rapid gain caused by methimazole can be regulated by instructed exercise.

A balanced diet and portion control:

By incorporating a healthy diet and eating in well-designated portions, you can overcome the habit of excessive eating as well as maintain your weight.

Low iodine-containing foods and healthy fats will have a positive effect on maintaining body composition. You can also introduce the following minerals and vitamins to enhance recovery:

• iron
• selenium
• vitamin D
• calcium
• zinc

However, do not take any supplements without the approval of your healthcare provider as they may interact with the therapeutic effects of the medication.

Seek counseling and professional help:

One of the best things you can do is to get advice from your healthcare provider as well as a nutritionist to get guidance on dietary habits and gain back your healthy mass.

Professional suggestions will help you manage weight properly while you stay on your regimen of methimazole.

In my experience:

As per my understanding, methimazole causes weight gain. It is an antithyroid medication used to treat hyperthyroidism which is characterised by excess thyroid hormone production.

The excess of thyroid hormone accelerates the body’s catabolic processes leading to increased weight loss. When this condition is treated with methimazole, patients experience weight gain.

Methimazole-induced weight gain is high in the initial months of the treatment and gradually reduces afterward. Lifestyle modifications and patient counseling help manage this side effect.

References