Can Hypothyroidism Cause “Brain Fog” & Mental Symptoms?

Do Thyroid Disorders Cause Forgetfulness and Brain Fog?

Can Hypothyroidism Cause “Brain Fog” & Mental Symptoms?

The thyroid is a gland in your neck that produces hormones that regulate growth and development. But, if it's not functioning well, problems with the thyroid can cause many challenges including extreme fatigue, weight loss or gain, rapid heartbeat, and hair loss.

Interestingly, both hypothyroidism and hyperthyroidism can also cause cognitive problems that can mimic symptoms of mild dementia.

Dementia is a blanket term which refers to a decrease in memory and other cognitive skills needed to perform routine activities of daily living.

The presentation of dementia varies from one person to another. Nevertheless, a person with dementia typically presents with at least two of the following symptoms:

Symptoms of mild dementia sometimes develop when thyroid levels are abnormal, but fortunately, they generally appear to resolve with treatment.

Hypothyroidism is a medical condition where not enough of the thyroid hormone is being produced.

Cognitive symptoms of people with hypothyroidism include memory problems and difficulty concentrating. Research has shown that verbal memory, in particular, may be affected by hypothyroidism. Another study found decreased hippocampal volume in adults with untreated hypothyroidism.

Small changes in executive functioning have also been noted in untreated or under-treated hypothyroidism. Executive functioning can include abilities such as planning, impulse control and making decisions. It's important to note, however, that larger changes in executive functioning are ly not related to hypothyroidism and thus should be reported to the physician.

Hyperthyroidism is when too much of the thyroid hormone is produced.

Some people with hyperthyroidism (also called Graves disease) commonly exhibit poor concentration, slower reaction times, decreased spatial organization and decreased visual processing skills.

Several researchers have questioned whether hyperthyroidism or hypothyroidism increases the risk for dementia to develop. Research on this question includes the following:

  • One study found that participants with subclinical hyperthyroidism (defined as TSH levels lower than 0.10 mIU/L) demonstrated a larger cognitive decline over the course of the research and an increased risk of dementia. There was not an increased risk in those with less significant TSH levels, nor was a risk correlated with subclinical hypothyroid levels.
  • A second study involved 1,750 older adults in Mexico. The researchers found that overt hypothyroidism was the condition most strongly connected to reduced cognitive functioning.
  • Researchers also took a look at several studies on thyroid function and cognition. They concluded that subclinical hyperthyroidism could be correlated with a risk of dementia; however, they also found that mini-mental state exam (MMSE) scores did not decline any faster with the presence of hyperthyroidism, hypothyroidism or normal thyroid functioning.
  • Another review of 13 different studies found that subclinical hypothyroidism was only correlated with an increased dementia risk in those who were younger than 75 and in those who had higher TSH levels.
  • In a post-mortem study of older adults, hypothyroidism that was treated was not found to increase the risk of Alzheimer's brain pathology. This doesn't indicate the actual cognitive functioning of the person, but it does demonstrate that a correlation was not found between actual brain changes of Alzheimer's and thyroid levels.
  • Yet another study found that hypothyroidism was not correlated with an increased risk of mild cognitive impairment. The researchers note that these results assume that hypothyroidism had been treated and thus that there does not appear to be any long-term effects on cognitive functioning.

In short, while the research doesn't all agree, several studies indicate that major cognitive problems are not ly to develop with hyperthyroidism or hypothyroidism. They also conclude that minor cognitive problems associated with thyroid functioning are often temporary.

Thus, if major cognitive decline is present, the physician should conduct a comprehensive assessment to determine what other medical conditions may be affecting your functioning.

Fortunately, there is an effective treatment available for those with thyroid problems. The thyroid hormone levels can be adjusted through the use of oral medications, radioactive iodine, and/or surgeries.

So, can this treatment help people with thyroid disorders who are experiencing cognitive problems? Although there is some question of the effectiveness of treatment with significantly older adults, most research shows that cognitive functioning improves when thyroid disorders are treated.

In fact, the good news, according to the Rancho Bernardo study, is that people who've been treated with supplemental thyroid therapy show no decline in cognitive functioning.

If you're experiencing forgetfulness or difficulty concentrating along with your thyroid concerns, be sure to convey these issues to your physician.

While you might initially feel embarrassed or uncomfortable about your brain fog, remind yourself that sharing this knowledge with your doctor helps the two of you be more effective as you work towards the goal of restoring your normal functioning.

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  1. Cooke GE, Mullally S, Correia N, et al. Hippocampal volume Is decreased in adults with hypothyroidism. Thyroid. 2014;24(3):433-440. doi:10.1089/thy.2013.0058

  2. Treated hypothyroidism, cognitive function, and depressed mood in old age: The Rancho Bernardo study. European Journal of Endocrinology. 2009;(161)917-921.

  3. Alzheimer's Association. What is dementia?

  4. MedlinePlus. Hyperthyroidism.

  5. Juárez-cedillo T, Basurto-acevedo L, Vega-garcía S, et al. Prevalence of thyroid dysfunction and its impact on cognition in older mexican adults: (SADEM study). J Endocrinol Invest. 2017;40(9):945-952. doi:10.1007/s40618-017-0654-6

  6. Pasqualetti G, Pagano G, Rengo G, Ferrara N, Monzani F. Subclinical hypothyroidism and cognitive impairment: Systematic review and meta-analysis. J Clin Endocrinol Metab. 2015;100(11):4240-8. doi:10.1210/jc.2015-2046

  7. Brenowitz WD, Han F, Kukull WA, Nelson PT. Treated hypothyroidism is associated with cerebrovascular disease but not Alzheimer's disease pathology in older adults. Neurobiol Aging. 2018;62:64-71. doi:10.1016/j.neurobiolaging.2017.10.004

  8. Parsaik AK, Singh B, Roberts RO, et al. Hypothyroidism and risk of mild cognitive impairment in elderly persons: a population-based study. JAMA Neurol. 2014;71(2):201-7. doi:10.1001/jamaneurol.2013.5402

  9. American Thyroid Association. Clinical Thyroidology for the public. Radioactive iodine therapy has the most favorable profile for the treatment of Graves’ disease at the Mayo Clinic. 2017;Vol 10 Issue 5 p.13-14.

Additional Reading

  • Memory improvement with treatment of hypothyroidism. International Journal of Neuroscience. 116:895-906, 2006.
  • American Thyroid Association. Thyroid disease in older patients.
  • Aubert C, Bauer D, da Costa B et al. The association between subclinical thyroid dysfunction and dementia: The health, aging and body composition (Health ABC) study. Clin Endocrinol (Oxf). 2017;87(5):617-626. doi:10.1111/cen.13458
  • Quinque E, Karger S, Arélin K, Schroeter M, Kratzsch J, Villringer A. Structural and functional MRI study of the brain, cognition and mood in long-term adequately treated Hashimoto's thyroiditis. Psychoneuroendocrinology. 2014;42:188-198. doi:10.1016/j.psyneuen.2014.01.015
  • Rieben C, Segna D, da Costa B et al. Subclinical thyroid dysfunction and the risk of cognitive decline: A meta-analysis of prospective cohort studies. The Journal of Clinical Endocrinology & Metabolism. 2016;101(12):4945-4954. doi:10.1210/jc.2016-2129
  • Samuels M. Thyroid disease and cognition. Endocrinol Metab Clin North Am. 2014;43(2):529-543. doi:10.1016/j.ecl.2014.02.006


What Thyroid Brain Fog Feels and How You Can Treat It

Can Hypothyroidism Cause “Brain Fog” & Mental Symptoms?

Can thyroid problems cause brain fog? Absolutely. In fact, thyroid brain fog is a common symptom of hypothyroidism and may even be one of the first clues that your thyroid isn’t functioning as it should be. If this is the case, you’re not alone.

According to the American Thyroid Association, an estimated 20 million Americans have some form of thyroid disease.

In addition, one woman in eight will develop a thyroid disorder during her lifetime, and women are five to eight times more ly than men to have thyroid problems.

Brain fog may occur with hypothyroidism because the brain requires adequate levels of thyroid hormone to function properly.

What is thyroid brain fog?

According to the National Academy of Hypothyroidism, the thyroid is a small gland located in the front of the neck.

It controls the body’s production, regulation, and distribution of thyroid hormones, which regulate the body’s metabolic rate as well as heart and digestive function, muscle control, brain development, mood, and bone maintenance. In other words, your thyroid influences nearly every function within your body.

Brain fog and thyroid problems often go hand in hand because thyroid function has a strong connection with metabolism. When your metabolism fluctuates, you may feel slow, lethargic, and lacking in energy.

When your energy level drops below a certain point, your brain is one of the first organs to feel the adverse effects. People with hypothyroidism (reduced thyroid function, also known as an underactive thyroid) often experience hypothyroid brain fog.

(Other symptoms of hypothyroidism include fatigue, weight gain, depression, dry skin, cold intolerance, muscle cramps, and constipation.)

“ATP [adenosine triphosphate] is a molecule that plays a key role in metabolism,” explains Barry Sears, PhD, president of the Inflammation Research Foundation. “In hypothyroidism, ATP production is decreased. Because the brain is the highest energy consumer per gram of weight in the body, it is most affected by an overall decrease in ATP production.”

(Photo Credit: Getty Images)

Thyroid Brain Fog Symptoms

Common thyroid brain fog symptoms include difficulty focusing and concentrating, and taking more time than usual to process or react to information.

“You may feel unmotivated, forgetful, or spacey,” says Mary Shomon, Thyroid Refresh advisory board member. “Your memory for names, numbers, and directions could be unpredictable.

You may even mix up words or have trouble recalling a common word.”

Patients with low thyroid brain fog often feel they can’t focus or concentrate to the point where everything feels blurry — as if they are in a fog.

“In addition to being frustrating, this can lead to sadness and depression, as well as worry and anxiety,” says Urszula Klich, PhD, licensed clinical psychologist and president of the Southeast Biofeedback and Clinical Neuroscience Association.

“People start focusing on their forgetfulness and errors, and worry about being able to be effective at home and work.”

Brain fog is also a common symptom of Hashimoto’s disease, additionally known as chronic lymphocytic thyroiditis, which is the most common cause of hypothyroidism in the United States.

According to the Mayo Clinic, this is a condition in which the immune system attacks the thyroid gland. This causes inflammation, which often leads to an underactive thyroid gland.

Women are much more ly to get Hashimoto’s disease than men, and the condition occurs most commonly during middle age.

What does thyroid brain fog feel ?

Are you still wondering, “What does brain fog feel ?”

“Imagine calling your child by the wrong name, forgetting your phone number or ZIP code, or realizing you have no idea where you are going while driving,” says Shomon. “These frightening memory lapses are common in people with thyroid problems. Thyroid patients call it brain fog, and doctors call it cognitive impairment — either way, it’s an all-too-common thyroid symptom.”

Underactive thyroid brain fog feels similar to hypoglycemia, says Sears. “It’s marked by confusion, an inability to concentrate, and a decreased focus on performing simple tasks.”

Brain fog makes navigating life extremely frustrating and understanding common situations impossible. For some patients, it is so severe that they are unable to participate in everyday conversation. It’s important to get medical advice if you think you have hypothyroidism and start thyroid brain fog treatment as soon as possible.

(Photo Credit: Getty Images)

Because the symptoms of hypothyroidism are often nonspecific and easily missed, and brain fog is often attributed to aging, stress, menopause, or some other cause, people with thyroid issues often go under the radar.

(Up to 60 percent of people with thyroid disease are unaware of their condition.

) Patients can only get a diagnosis of underactive thyroid by having a doctor look at symptoms in their totality and carry out the necessary tests..

Treatment starts with an appointment with your physician for a thorough checkup and to determine whether you have hypothyroidism.

“Your doctor should take your medical history, examine your thyroid, and order a complete thyroid blood test panel,” advises Shomon.

“If your doctor diagnoses you with hypothyroidism, treatment with a prescription thyroid drug may quickly and easily resolve your brain fog.”

If you are already being treated for hypothyroidism but still have brain fog, you may need more aggressive thyroid treatment.

Shomon suggests talking to your doctor about increasing your thyroid medication or adding a medication Cytomel to your standard levothyroxine (e.g., Synthroid or Levoxyl) treatment.

“You may need to switch to a natural desiccated thyroid drug Armour or Nature-thyroid to resolve your brain fog,” she says.

If you think you have brain fog from medication (taken for a thyroid issue or other health issue), talk to your doctor about alternatives.

“As well as thyroid medication, stabilization of blood sugar through a balanced diet also helps produce more ATP in the brain,” says Sears. “Ultimately, people with thyroid and brain fog issues should understand that it is a real metabolic event that can be treated with the appropriate hormones and dietary changes.”

Often, inflammation starts in the gut, the home of most of the body’s immune system. Improving gut health is one way to improve the efficacy of the immune system, which can have a positive effect on brain and thyroid function.

Reducing or eliminating inflammatory foods and substances processed meat, alcohol, caffeine, refined carbohydrates, and artificial trans fats may help improve gut function, and reduce gastrointestinal stress. Adding a probiotic to your diet can also improve gut function by encouraging the production of good bacteria.

(Photo Credit: Getty Images)

As well as getting proper medical care for thyroid brain fog, Klich offers the following tips for taking care of your body and mind to help improve your brain function:

  • Be sure to get restful sleep and exercise.
  • Think of accepting help from others as a gift to yourself. Not accepting help may mean not getting your needs met, leading to more loss (and denying others the joy and benefits of giving).
  • Improve communication skills to reserve your much-needed cognitive energy in the long run. For example, setting healthy boundaries for what you can commit to can help you reserve cognitive energy.
  • People with hypothyroidism find themselves feeling drained in many ways and are often “sick and tired of feeling sick and tired.” This is normal, but watch out for negative thinking. It is easy to turn frustration related to altered abilities into negative expectations about yourself that you begin to believe. Saying things , “I should not be this upset,” or, “I’m mad at myself for being tired,” or, “I’ve got to get a handle on myself,” simply leads to increased feelings of inadequacy.
  • Stress has been shown to limit our executive functioning and decrease our cognitive abilities, which results in difficulty with memory, attention, and concentration. Make stress relief part of your everyday life, whether it takes the form of yoga, meditation, running, reading, taking a long bath, or listening to podcasts.

Klich also suggests these quick strategies for coping with cognitive challenges to make everyday tasks a little easier:

  • Set up some type of organization system that works for you.
  • Use Sticky Notes as reminders, and keep them with you at all times.
  • Always keep keys, glasses, watches, and your purse/wallet in the same spot.
  • Make good use of your computer, electronic devices, and smartphones.
  • Plan mental tasks when you have the most energy in the day.
  • Reduce distractions (such as noise from the TV) when you’re trying to concentrate.
  • Write things down in an organized way.
  • Do one thing at a time.
  • Talk honestly with friends and family about your difficulties because communication can reduce stress and increase your ability to cope.

Finally, if you find that your thyroid brain fog is interfering significantly with your decision-making, sleep quality, work, relationships, or quality of life, don’t hesitate to make an appointment with your doctor, talk to a counselor, or seek other guidance.

This post was written by Claire Gillespie.

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Thyroid Brain Fog

Can Hypothyroidism Cause “Brain Fog” & Mental Symptoms?
This post may contain affiliate links, to find out more information, please read my disclosure statement.

Originally published on 29th April 2016 Last updated on 26th November 2019

Thyroid brain fog is real. Oh, it’s real alright.

You can read the lighter side of my brain fog experiences here, but in this post, I’m going to explore how and why thyroid patients experience it among their many other symptoms.

What is Brain Fog?

Brain fog is often described as feelings of mental confusion or lack of mental clarity. The phrase comes from the feeling of a fog that reduces your ability to think clearly. It can feel a mental block. It can cause a person to become forgetful, detached and discouraged and even depressed as a knock on effect.

Brain fog is a common symptom of thyroid problems, particularly hypothyroidism.

Read how thyroid patients commonly describe their brain fog here.

Low Thyroid Hormone Levels 

Thyroid hormones T3 and T4, used by the brain, have major influences over virtually every brain activity. So if a thyroid patient doesn’t have enough of these thyroid hormones in their body, brain fog often occurs, to varying degrees.

At times, mine was so severe that it seriously impacted my ability to work. I could read an email ten times and it still wasn’t registering in my mind.

Ensure that both your Free T3 and Free T4 are optimised and not just ‘normal’, ‘fine’ or ‘in range’.

Thyroid hormone, particularly T3, has an important role in the health and optimal functioning of your brain, including: cognitive function, the ability to concentrate, mood, memory and attention span.

This explains why we can experience symptoms such as brain fog.

T3 interacts with brain receptors and makes the brain more sensitive to chemicals such as serotonin and norepinephrine, which affects your alertness, memory, mood and emotion.


Inflammation in the body can mean all sorts of things, from a leaky gut, to gluten sensitivity and Hashimoto’s, and brain fog could be an indication of inflammation in the brain.

Dr Datis Kharrazian also comments on how Hashimoto’s, which around 90% of hypothyroid patients have [1], can cause inflammation in the brain, leading to symptoms brain fog. I watched a seminar on this at the Healing Hashimoto’s summit, 13th-20th June 2016.

Being hypothyroid means you have a high chance of also having an autoimmune disease Hashimoto’s, so cutting out gluten may also help with inflammation.

Mental Health 

Since depression can also cause symptoms of brain fog, receiving adequate treatment for that and treating any underlying conditions is also important. Many thyroid patients are also on antidepressants. My depression was caused by an inadequately treated thyroid problem, so once my medication was right for me (switching to NDT), my depression lifted.

Vitamin Levels 

Explore Vitamin B12, D, iron, ferritin etc. too to rule out other causes for brain fog and similar thyroid symptoms.

Some thyroid patients also swear by magnesium supplementation for improving brain fog.

Poor Gut Health

I experienced an impressive reduction in brain fog after overcoming candida (yeast overgrowth) and gut permeability with a functional medicine practitioner.

With leaky gut, the intestinal barrier of the gut becomes permeable from hypothyroidism, infections, food intolerances (especially gluten) or even stress, allowing food particles to slip through and circulate round the rest of the body.

This can lead to your microglia, who work to defend your central nervous system, going in to high alert – leading to inflammation in the brain.

Addressing any gut issues is crucial for overall thyroid health, and the first step many thyroid patients make to improve this is by removing offending foods from their dit, such as gluten and dairy, which alone can improve brain fog a lot.

A UK test for Candida can be found here. and a US test here.

Blood Sugar Imbalances

Symptoms of blood sugar issues can include headaches, feeling faint and dizzy, feeling hungry again quickly after eating, feeling tired, grouchy, irritable and foggy minded.

One of the simplest things you can do to improve any thyroid symptoms you have is to learn how to keep your blood sugar balanced. Since realising that I needed to adjust my diet to allow more protein and fat (and less sugar and carbs) in order to balance my blood sugar better, my low blood sugar bouts, irritable moods, groggy feeling, brain fog and slumps are gone.

Healthy fats play a big role in our mental health, mood and brain function. Good sources of fat include olive oil, sesame oil, avocados, olives, nuts, seeds, peanut butter, flaxseed, salmon, chia seeds, eggs and even seed butter.

I also ensure I consume enough protein with every meal and snack, in order to keep my blood sugar levels balanced; sources of protein can include meats, cheese, eggs, nuts, seeds, yoghurts, beans and legumes.

We should aim to eat every two to three hours to keep blood sugar levels balanced. Going long times without food, such as fasting, can place extra stress on the adrenal glands. Never skip meals.

What Helped Remove My Brain Fog

Going gluten-free dramatically improved my brain fog, but things addressing low iron levels and low Vitamin D levels also helped. As well as addressing my gut health, diet and eating to better balance blood sugar levels.

Keep nudging your doctor for more reasons as to what is causing your brain fog if you still have no joy with any of the above tips. It’s often one of the most debilitating symptoms of being hypothyroid.

Do you experience thyroid brain fog?

See also:

The book Be Your Own Thyroid Advocate: When You’re Sick and Tired of Being Sick and Tired, which builds on this article in detail and covers the simple things you can do to resolve thyroid symptoms.

You can click on the hyperlinks in the above post to learn more and see references to information given, but more reading and references can also be found at:



If you found this article beneficial, please take a moment to share it so we can help others get better with hypothyroidism and Hashimoto's, whilst also raising awareness. “Be Your Own Thyroid Advocate.”

Written by Rachel, The Invisible Hypothyroidism

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