Can thyroid disease cause forgetfulness and brain fog?

Do you feel like you forget things more often, or as if your brain is covered in fog?

Memory loss has many causes, some linked to Alzheimer’s disease or other dementias. Others are due to potentially reversible causes, one of which is thyroid disease.

This article explains the link between the thyroid and memory, and how hypothyroid and hyperthyroid thyroid disorders mimic the symptoms of dementia. It also identifies drugs often used to treat thyroid disease, as well as two more aggressive options.

Thyroid and memory

The thyroid is a gland in the neck that produces hormones that regulate growth and development. If your thyroid is not functioning properly, it can cause many problems. They include extreme fatigue, weight loss or gain, rapid heartbeat, and hair loss.

Hypothyroidism (an “underactive” thyroid) and hyperthyroidism (an “overactive” thyroid) can also cause cognitive problems, similar to the symptoms of mild dementia.

What is dementia?

Dementia is an umbrella term that refers to not one but several disorders that cause the loss of memory and other cognitive skills needed to perform basic activities of daily living. Alzheimer’s disease is probably the best-known type of dementia.

The way dementia “presents” itself varies from person to person. But people with dementia usually show at least two of the following symptoms:

  • alter visual perception
  • difficulty concentrating or concentrating
  • Impaired reasoning and judgment
  • communication and language barriers
  • memory loss
  • misplaced object

Symptoms of mild dementia sometimes appear when thyroid levels are abnormal, but they usually seem to go away with treatment.

Cognitive symptoms of hypothyroidism

Women are three times more likely than men to have hypothyroidism — a condition in which the body doesn’t produce enough thyroid hormone.

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Cognitive symptoms in people with hypothyroidism include memory problems and difficulty concentrating.

The researchers aren’t entirely sure why these problems occur, but they do know that “hypothyroidism affects memory because thyroid hormones work in areas of the brain that are critical to our memory and cognitive skills.” When thyroid hormone production slows, people feel it “through brain fog.”

Small changes in executive function are also noted in untreated or undertreated hypothyroidism. Executive functions include abilities such as planning, impulse control, and decision-making.

Cognitive symptoms of hyperthyroidism

Hyperthyroidism occurs when your thyroid produces more thyroid hormones than your body needs.

Some people with hyperthyroidism (also known as Graves’ disease) often exhibit poor concentration, slower reaction times, reduced spatial organization, and memory loss.

Thyroid medication can help

Fortunately, there are effective treatments available to people with thyroid problems, including medication:

  • People with hypothyroidism are often prescribed Levothyroxine. Sodium tablets contain a synthetic hormone to mimic Thyroxineproduced naturally by the thyroid gland.
  • Commonly used by patients with hyperthyroidism methimazole or propylthiouracil. Neither is curable, and many people take medication for life.

If you’re taking one of these pills, the Thyroid Foundation UK says there’s good reason to be optimistic: “Fortunately, in the vast majority of cases, psychological symptoms will improve as thyroid disease is managed with treatment.”

Two other treatment options

Thyroid medication may be the easiest treatment, but two other strategies can relieve an underactive or overactive thyroid:

  • Radioactive iodine therapy involves oral radioactive iodine, either in capsule or liquid form. Treatment is slow but sure to destroy the thyroid cells that produce thyroid hormone. (it leaves only other body tissues).
  • Part or most of the thyroid can be removed surgically. Thyroid surgery is a last resort, but it may be a good option for pregnant women who cannot take thyroid medication.
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Thyroid problems and dementia risk

Some researchers have questioned whether hyperthyroidism or hypothyroidism can increase the risk of dementia. Findings on this issue include the following:

  • One study found that participants with subclinical hyperthyroidism (defined as TSH levels below 0.10 mIU/L) exhibited greater cognitive decline and increased risk of dementia over the course of the study. There was no increased risk in patients with insignificant thyroid-stimulating hormone (TSH) levels. Too much TSH can signal hyperthyroidism, while too little can signal hypothyroidism.
  • The researchers also looked at several studies on thyroid function and cognition. They concluded that subclinical hyperthyroidism may be associated with dementia risk. However, they also found that Mini-Mental State Exam (MMSE) scores did not decline any faster in the presence of hyperthyroidism, hypothyroidism, or euthyroidism.
  • Another review of 13 different studies found that subclinical hypothyroidism was associated with an increased risk of dementia in people under the age of 75 and in those with higher TSH levels.
  • In autopsy studies of older adults, treatment for hypothyroidism was not found to increase the risk of Alzheimer’s brain lesions. This does not indicate the person’s actual cognitive function, but it does indicate that no correlation has been found between actual brain changes in Alzheimer’s and thyroid levels.
  • Another study found that hypothyroidism was not associated with an increased risk of mild cognitive impairment. The researchers noted that these results assume that hypothyroidism has been treated and therefore does not appear to have any long-term effects on cognitive function.

In short, while the findings may be inconsistent, it seems Considerable Cognitive problems are less likely with hyperthyroidism or hypothyroidism. Minor cognitive problems related to thyroid function, such as forgetfulness and brain fog, are usually temporary.

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Finally, if you exhibit severe cognitive decline, your healthcare provider should conduct a thorough evaluation to determine if other medical conditions may have contributed to your current state.


Appearing forgetful can be embarrassing. But if you’re dealing with thyroid disease, you should take it easy: If your thyroid isn’t working properly, it can cause memory problems. Symptoms of an overactive and underactive thyroid can look like mild dementia, and problems with concentration and memory are red flags. The good news is that medications can control both hypothyroidism and hyperthyroidism.

VigorTip words

Be sure to alert your healthcare provider if you experience forgetfulness or difficulty concentrating and thyroid problems. While you may initially feel embarrassed or uncomfortable with your brain fog, remind yourself that sharing this knowledge with your healthcare provider can keep both of you working toward your goal of returning to normal function.

Frequently Asked Questions

  • Are Thyroid Problems Linked to Increased Risk of Dementia?

    possible. Research on thyroid and dementia risk is mixed.

    It appears that both high and low TSH levels increase the risk of dementia in people under the age of 75. However, taking medication to restore thyroid hormone levels to the normal range can eliminate the increased risk of dementia.

  • Is memory loss from hypothyroidism reversible?

    Mostly right. Treating hypothyroidism or hyperthyroidism with medications that adjust thyroid levels can help you think more clearly. Cognitive function did not decline in those who received thyroid supplementation. However, it is unclear whether thyroid treatment helps memory problems in adults over 75.