Relationship Between Thyroid Dysfunction and Body Weight At Baseline and After Normalization of Hormone Levels

Relationship Between Thyroid Dysfunction and Body Weight At Baseline and After Normalization of Hormone Levels

Thyroid problems tend to manifest themselves through changes in body weight.


For instance, hypothyroidism is associated with weight gain, while hyperthyroidism often leads to weight loss.


Why do those changes happen?


In this article, we are going to explore the relationship between thyroid problems and body weight.


What happens when thyroid levels return to normal?


Thyroid and body weight

Even though thyroid problems are associated with weight changes, most people don't know how it happens.


In order to discuss the relationship between thyroid hormones and body weight, it's necessary to address all the mechanisms involved.


The truth is that body composition, and thyroid hormones are more closely related than most of us could imagine. Thyroid hormones regulate basal metabolism and thermogenesis.


They participate in lipid (fat) and glucose (blood sugar) metabolism and also play a role in food intake and fat oxidation.


Evidence shows that thyroid dysfunction with changes in body weight, composition, temperature, as well as resting energy expenditure.


In fact, the influence of thyroid dysfunction on all these factors is independent of physical activity.


Let’s take a closer look into common thyroid problems and their impact on body weight.


Hypothyroidism and body weight

Hypothyroidism is a common thyroid disorder characterized by decreased production of T4 and T3 hormones. The condition induces a number of symptoms, and weight gain is one of the most prevalent changes that patients experience.


Hypothyroidism is strongly associated with reduced thermogenesis, lower metabolic rate, and it also contributes to higher BMI and increased prevalence of obesity. It’s easy to think that severe hypothyroidism can induce all these changes and make people gain weight, but that’s not quite correct.


Even small changes in thyroid hormones such as subclinical hypothyroidism can still cause weight gain[i].


Due to low metabolic rate, it is generally assumed that patients with overt hypothyroidism are overweight, and their weight tends to increase as the disease progresses to severe hypothyroidism.


In one study, patients with newly diagnosed overt autoimmune hypothyroidism weighed on average 7kg more than their euthyroid counterparts. It was revealed that the main mechanism behind such an increase in body weight is not all down to fat, but an enlarged water compartment.


In other words, hypothyroidism can contribute to water retention, which means that overweight is not entirely down to increased body fat.


Weight changes that occur due to hypothyroidism are not a result of a single biochemical factor, but it’s more likely that a combination of different effects plays a role. As mentioned above, thyroid hormones slow down metabolism. They do so through interaction with your muscle, liver, fat cells, hypothalamus, and pancreas.


Hormones produced by the butterfly-shaped gland break down fat, but they also help your pancreas and liver metabolize stored calories that your body uses for energy. Thyroid hormones also participate in the process wherein muscles use energy. Normal levels of thyroid hormones the hypothalamus reduces the amount of TRH secretion.


Thyroid dysfunction, such as hypothyroidism, impairs all these processes. Metabolism slows down, your body doesn’t break down fat properly, and a domino effect occurs with weight gain as the final outcome.


Weight management is crucial for people with hypothyroidism because being overweight or obese can worsen other symptoms of this condition. Hypothyroidism is treated with levothyroxine, which helps to normalize thyroid hormone levels.


Hyperthyroidism and body weight

Hyperthyroidism is a thyroid disorder indicated by abnormally high levels of hormones. Unlike hypothyroidism, which leads to weight gain, hyperthyroidism causes weight loss.


Weight loss in hyperthyroid men and women occurs due to faster basal metabolic rate. In other words, hyperthyroidism speeds up metabolism, unlike hypothyroidism, which slows it down.


The likelihood of weight loss has a lot to do with the severity of the overactive thyroid. People with moderate to severe hyperthyroidism are more likely to lose a significant amount of weight than patients whose overactive thyroid problem is relatively mild.


If you don't increase the calorie intake in order to compensate for calories the body burns, then weight loss will happen.


Normalization of hormone levels and body weight

So, what happens after normalization of hormone levels?


Does weight change as well?


It turns out, and it's not so simple!


Rios-Prego et al. evaluated the association between thyroid dysfunction and BMI at baseline and after normalization of the hormone levels. They selected 330 subjects for the study initially, but in order to exclude all variables that could interfere with BMI, they excluded all but 34 participants.


Results showed that no differences in mean baseline BMI between hypo- and hyperthyroidism patients were observed. Moreover, 76.5% of hypothyroid patients were overweight or obese at baseline, while 58.8% of hyperthyroid participants had this weight problem.


After normalization of thyroid hormone levels subjects with hypothyroidism lost weight (about 2kg) while hyperthyroid participants increased weight (about 3kg on average). Scientists concluded that untreated thyroid dysfunction is not associated with BMI. While normalization of thyroid hormone levels induced certain weight changes in participants, but most subjects remained within overweight ranges[ii].


In other words, the study whose findings were published in April 2019, found that normalization of thyroid hormone levels didn't really help patients lose a significant amount of their weight.


Bear in mind that this doesn't mean you can't achieve a healthy weight if you're diagnosed with some thyroid problem and working to normalize levels produced by the butterfly-shaped gland.


It just means more effort is necessary; we can't rely on thyroid disorder treatment as our gateway to a healthy weight.


Plus, we need to have realistic expectations. According to the American Thyroid Association, patients with hypothyroidism can expect to lose about 10% of body weight after their thyroid hormone levels are normalized. While treatment of hypothyroidism should ideally result in the return of body weight a person had before the condition developed, things are more complicated than that. The reason is simple; we do not develop hypothyroidism overnight.


We don't wake up one morning being hypothyroid. This condition develops gradually over a period of a few years, so it's highly unlikely that whole weight gain is due to hypothyroidism only[iii].


On the other hand, patients with hyperthyroidism are expected to gain all the weight they lost when their thyroid hormones were at abnormally high levels. Hoogwerf and Nuttall studied 87 participants treated for hyperthyroidism with radioiodine and/or anti-thyroid drugs.


They followed participants for 7.5 years after their therapy. Patients had their body weight measured before the therapy and during the follow-up. Scientists found that after therapy, bodyweight started increasing. At 24 months after the initial therapy, subjects had about the same weight, they had before they have become hyperthyroid. Furthermore, their body weight started slightly increasing, and about eight years after therapy it was 1.7kg higher on average[iv].


Euthyroid and body weight

Now that we have addressed the link between hypo- and hyperthyroidism with body weight, it's also impossible not to wonder whether normal thyroid hormone levels have any impact on our weight. The state of having normal thyroid gland function is called euthyroid. While hypothyroidism and hyperthyroidism in relation to weight changes are studied extensively, euthyroid is not. However, evidence still exists.


ISRN Biomarkers published a study which explored the relationship of fluctuations of thyroid hormones and TSH with BMI in euthyroid subjects. For the purpose of the study, scientists included 736 euthyroid subjects of whom 616 were women and 118 men. All participants were clinically healthy. Scientists found that the relationship between BMI and various thyroid hormones different in men and women. For instance, a statistically significant relationship between BMI and thyroid hormones T3 and T4 was observed in women.


On the other hand, in men BMI was related to FT3 and negatively associated with TSH. Scientists elaborated that normal thyroid function could be associated with changes in BMI, but the relationship is not quite clear. One potential mechanism that could explain the influence of euthyroid on weight is the change in resting energy consumption[v].


As you can see, thyroid hormones can induce weight changes, but more studies are needed to uncover all mechanisms and learn more about this relationship.


Losing weight with hypothyroidism

As mentioned above in the article, hypothyroidism is strongly associated with weight gain. It seems that overweight and hypothyroidism influence one another, and their management is vital.


Managing hypothyroidism could help you slim down, and weight loss would decrease the severity of other symptoms of this condition. Just bear in mind that many other factors contribute to weight gain, not just thyroid.


To boost your weight loss efforts, you will need to make some lifestyle modifications. These tips can help you lose weight with hypothyroidism:


  • Eat a healthier diet – your nutrition plays an important role in hypothyroidism and weight management. Make sure to minimize simple carbs and sugars and focus on the intake of lean proteins, anti-inflammatory foods, and vegetables. Also, you need to avoid trans fats and pretty much other foods with little to no nutritional value
  • Exercise regularly – physical activity and a healthy diet should go hand in hand. Exercise can aid hypothyroidism management and, as you're already aware, it is crucial for weight loss too. Ideally, you should strive for 150 minutes of moderate exercise and two sessions of muscle-building workout on a weekly basis. Choose activities you like because that way you will be more likely to stick to them. In addition to exercise, you may want to move more e.g., take stairs instead of the elevator, don't park near work and use the opportunity to walk a little bit, do house chores, options are endless
  • Get enough sleep – unfortunately, we have become a sleep-deprived society, but lack of good night’s rest can contribute to weight gain. Ideally, you should sleep seven to nine hours each night. Regular sleep schedule can help you achieve that goal. Bear in mind it’s not just about getting nine hours of sleep, but also about going to bed every night at the same time and waking up every morning at the same time as well
  • Manage stress – stress is linked to sleep deprivation, weight gain, thyroid hormone problems; you name it. Instead of ignoring the stress, you should find a unique way to manage it. Do something you find relaxing e.g., take deep breaths, read, write, exercise, and there are many ways to tackle stress and boost your weight loss efforts
  • Stick to the treatment – a common mistake that many people repeat is that they do not adhere to the hypothyroidism treatment as closely as they should. As soon as they feel like things are getting better, they assume medications are not necessary anymore. Don't do that! Always stick to the treatment your doctor recommended because your healthcare provider will inform you if it's okay for you to stop or take a lower or higher dosage. Failing to adhere to hypothyroidism treatment could negatively affect your weight loss effort



Thyroid gland participates in many functions in the body and is strongly related to our body weight. Studies have shown that the butterfly-shaped gland influences body weight through multiple mechanisms.


That's why problems with thyroid can make people gain or lose weight. Normalization of thyroid hormone levels doesn't always lead to the return of body weight a person had before, particularly in hypothyroid people.


The reason is simple, hypothyroidism develops over a few-years period, and many other factors could cause weight gain too.


That's why it's important to have a healthy lifestyle, eat a well-balanced diet, exercise regularly in order to have a more successful weight loss.




[i] Sanyal, D., & Raychaudhuri, M. (2016). Hypothyroidism and obesity: An intriguing link. Indian journal of endocrinology and metabolism20(4), 554–557. doi:10.4103/2230-8210.183454. Retrieved from:


[ii] Rios-Prego M, Anibarro L, Sanchez-Sobrino P. (2019). Relationship between thyroid dysfunction and body weight: a not so evident paradigm. International Journal of General Medicine, 12;299-304. Doi: 10.2147/IJGM.S206983. Retrieved from:


[iii] Thyroid and weight, American Thyroid Association. Retrieved from:


[iv] Laurberg, P., Knudsen, N., Andersen, S., Carlé, A., Pedersen, I. B., & Karmisholt, J. (2012). Thyroid function and obesity. European thyroid journal1(3), 159–167. doi:10.1159/000342994. Retrieved from:


[v] Milionis A, Milionis C. (2013). Correlation between body mass index and thyroid function in euthyroid individuals in Greece“. ISRN Biomarkers, 2013, Article ID 651494. Doi: 10.1155/2013/651494. Retrieved from:

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