Of all the advice out there about Hashimoto’s and hypothyroidism, one of the most important areas you need to focus on is often overlooked – muscles! Building lean muscle mass is one of the best things you can do to successfully manage Hashimoto’s.
This article is all about the benefits that having more muscle can give you and why it works.
How Hypothyroidism and Levothyroxine Treatment Affect Muscles
Hypothyroidism comes with a host of muscle issues, including :
- Muscle pain (myalgia) and cramps
- Muscle fatigue
- Muscle weakness
- Muscle wasting (atrophy)
Up to 80% of people with hypothyroidism will experience neuromuscular symptoms. Some of these will persist even after thyroid levels are normalized with treatment.[2,3]
Muscle loss can also lead to sarcopenia (age-related muscle loss) and other related health issues such as frailty, falls, and reduced mobility down the line.
Thyroid hormones are required for every metabolic process in your body including cell metabolism, growth, and tissue development. 
Skeletal muscle is one of the largest endocrine organs in the body and is a major target of thyroid hormone. [5,6] Without enough thyroid hormones, muscles will begin to atrophy. This can lead to sarcopenia where the muscle loss from hypothyroidism compounded with aging result in other health issues down the line. Also, a lot of thyroid hormone activation happens in your muscle tissues, so the less muscle tissue you have, the harder it’ll get to successfully manage Hashimoto’s. This is why it’s important to work on gaining and maintaining muscle mass.
With low thyroid function, your muscle cells will be under-functioning. This creates weakness and wasting, and whatever muscle tissues are still left will also be easily fatigued due to low energy. This can make simple tasks of daily living like picking up laundry off the floor, doing dishes, or going up and down the stairs difficult.
Thyroid hormone replacement therapy, especially levothyroxine, is typically a necessary standard treatment, and it often results in some minor initial weight loss. Clinical studies show that the lost weight with this thyroid hormone replacement tends to include both fat and lots of muscle tissue. [7–9] Overall, being hypothyroid and on thyroid hormone replacement may cause more muscle mass loss than if you never had hypothyroidism at all.
As an example, let’s consider two women, A and B, who start off at 25% body fat and 30% muscles. A develops hypothyroidism and starts to gain fat and lose muscles in 6 months so she’s at 25% muscle mass and 35% body fat by the time she’s diagnosed. A then gets on thyroid medication without resistance training or eating enough proteins, and she loses some weight in 6 months. Now A is at 23% muscle mass and 33% body fat, while B is still at 25% body fat and 30% muscles. So, while it seems that thyroid medications may accelerate muscle mass loss, it just results in some loss which combines both muscle and fat.
The good news is that resistance training and nutrition can mitigate or reverse the muscle loss associated with Hashimoto’s and hypothyroidism.
Muscle loss and atrophy worsen the overall picture for Hashimoto’s and your health. Having less muscle mass means you’ll experience worse fatigue and joint pain, your inflammation and antibodies will be higher, and overall you may take longer to achieve remission. Therefore, I believe resistance training and nutrition should be key to managing and thriving with Hashimoto’s.
Now that you know how Hashimoto’s and levothyroxine can affect your muscle mass, let’s look at how having good muscle mass can help with Hashimoto’s.
How Having Good Muscle Mass Helps with Hashimoto’s
Having good muscle mass provides all kinds of benefits when you have Hashimoto’s, many of them lifesaving.
Improves thyroid hormone conversion
Many hypothyroid patients still feel the symptoms even after they get enough levothyroxine that their labs are normal. Part of this has to do with low thyroid conversion. The hormones your thyroid glands produce (T4) need to be converted into the active form (T3) in muscles and other tissues.
The inactive T4 thyroid hormone, whether naturally produced or taken in prescription form (levothyroxine), has to get converted to the active thyroid hormone T3. This conversion largely takes place in the liver and skeletal muscles. Having more muscle mass leads to more T3 conversion, which means you have more of what your body needs to function. 
May improve response to thyroid medications
If you are on thyroid medications, you may remember the awful period when your doctor was still figuring out the right dose for you. You’ve finally been diagnosed and prescribed medication, but your symptoms and labs aren’t stabilized yet.
Having more muscle mass can significantly shorten this duration. The more muscle mass you have, the faster you will reach this stable dose for your thyroid medications. 
Maintains healthy metabolism and helps with weight loss
Muscle cells are very metabolically active–they burn a lot more calories than your fat cells do. Having more muscle mass increases your basal metabolic rate (BMR).  This means you’ll burn more calories even when you’re sitting down and doing nothing!
More importantly, the process of building muscle mass in your body burns a lot of calories. This means you can (reasonably) eat more without gaining fat while looking better by the day. In some cases, you’ll be able to gain muscle mass and lose fat at the same time if you’re very new to lifting and eating for muscle gain.
Improves blood sugar control and health risk from insulin resistance
Women with Hashimoto’s are also at a much higher risk of all kinds of diseases related to poor blood sugar control, including [15,16]:
- Polycystic ovarian syndrome
- Metabolic syndrome and diabetes
- Cognitive impairment and Alzheimer’s disease
- High cholesterol and heart disease
Therefore, regularly lifting weights and building muscle mass will not only reduce belly fat but also improve your blood sugar control. Overall, it will reduce your risks of all kinds of chronic diseases that poor blood sugar control can lead to.
Reduces inflammation and autoimmunity
Muscles modulate immune function and inflammation throughout your body. Your muscles constantly talk to your immune system and make it more resilient. 
Muscles produce immune system messengers that are very anti-inflammatory and inhibit autoimmunity. [18,19] Through this and other ways, the more muscle mass you have, the better your inflammation will be controlled.[20,21] This may translate into lower levels of pain and Hashimoto’s activity.
Stabilizes joints and reduces pain
Aside from inflammation, joint hypermobility is another cause of joint pain in Hashimoto’s. Muscles stabilize joints and protect them from overextending. This prevents injury and reduces compensating tightness in your body that causes pain.
Improves overall day-to-day function, promotes healthy aging, and prevents premature death
The bodily pain and intense fatigue with Hashimoto’s can really take away from wanting to be the best parent you can be or simply living a functional life. While the default response is to move less and rest as much as possible, this only makes things worse.
As you age, sarcopenia (muscle loss) can be a real health threat. It increases your risk of life-threatening infections and falls, along with all kinds of age-related diseases. 
Muscles are anti-aging. They make you look younger and improve your overall well-being.
How to Build Muscles despite Hypothyroidism
Because Hashimoto’s can reduce your muscle mass, it makes good sense to build strength and lift weights to maintain and build muscles. This article lists the key ingredients to building and maintaining muscles wherever you are on your Hashimoto’s journey.
There is so much misguided exercise advice out there for women with Hashimoto’s. This is why I created Thyroid Strong after spending over 10 years figuring out the right way to exercise and eat to lose weight and build muscles without making my Hashimoto’s symptoms worse. It includes lifting guides, nutrition plans, expert interviews, and more so you can comprehensively address the root causes of your Hashimoto’s.
Aside from lifting correctly and eating right, building muscles with hypothyroidism takes consistency and dedication. You may not feel like it at first, and the gym can be intimidating if you have been out of shape for a while. This is why Thyroid Strong also comes with community support from women like you. We can commiserate with your struggles and symptoms, but at the same time keep you accountable to consistently put in the work.
Thyroid Strong will help you thrive with Hashimoto’s, whether your goal is to put it into remission, live your full life, or lose weight and look better.
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