Do Thyroid Disorders Cause Memory Loss and Brain Fog?

The Effects of Hypothyroidism and Hyperthyroidism on Cognition

How the Thyroid Can Affect Memory
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Feeling like you're forgetting things more often, or your brain is in a fog? There are many causes of memory loss, and while some are related to Alzheimer's disease or other dementias, others are due to potentially reversible causes, one of which is a thyroid disorder.

What Is the Thyroid?

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.

What Is Dementia?

Many people incorrectly think that dementia is some specific type of disease. However, dementia is a blanket term which refers to a decrease in memory and other cognitive skills needed to perform routine activities of daily living.

Alzheimer's disease is just one form of dementia, and according to the Alzheimer's Association, it accounts for 60 to 80 percent of all cases of dementia. Another common cause of dementia is vascular dementia which occurs after a stroke, or when blood supply to the brain is compromised.

The presentation of dementia varies from one person to another. Nevertheless, a person with dementia presents with at least 2 of the following symptoms:


Hypothyroidism is a medical condition where not enough of the thyroid hormone is being produced. People with low thyroid levels may feel tired, gain weight, and experience dry, itchy skin and constipation.

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.


Hyperthyroidism is when too much of the thyroid hormone is produced. Symptoms may include feeling jittery, unintended weight loss, and heart flutters.

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

Prevalence of Thyroid Disorders

It's estimated the 200 million people worldwide suffer from a thyroid disorder, although it's difficult to know for certain because many go undetected. We do know that as people age, it's more likely that they'll develop a thyroid disorder; however, many younger adults develop thyroid problems as well.


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.

Does Treatment Reverse or Prevent Cognitive Problems?

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

Further Information on Thyroid Disorders

Please visit Verywell's overview on thyroid disorders for in-depth information on different thyroid disorders, symptoms and treatments.


American Thyroid Association. Thyroid Disease in Older Patients.

European Journal of Endocrinology. December 1, 2009 161 917-921. Treated hypothyroidism, cognitive function, and depressed mood in old age: the Rancho Bernardo Study.

International Journal of Neuroscience. 116:895-906, 2006. Memory Improvement with Treatment of Hypothyroidism.

The Journal of Neuropsychiatry and Clinical Neurosciences, VOL. 19, No. 2. Verbal Memory Retrieval Deficits Associated With Untreated Hypothyroidism. 

Thyroid. 2001 Dec;11(12):1177-85. Hypothyroidism and cognition: preliminary evidence for a specific defect in memory.

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