Hypothyroidism and Memory

According to the National Institutes of Health, about 4.6% of the US population older than 12 has hypothyroidism although most cases are mild. In other words, 5 out of 100 people in the United States are hypothyroid[i] which is quite worrying when you consider the total population of the country. Hypothyroidism is characterized by a wide array of symptoms, and it affects our body in many ways. The condition is strongly associated with changes in a person’s memory. How does hypothyroidism affect memory and is there anything you can do about it? Keep reading to find out.

Thyroid hormones and memory

Even though we don’t usually consider thyroid as a factor in brain functions the studies have shown this butterfly-shaped gland plays a role in cognitive abilities and memory. Rivas et al. found that thyroid hormones are vital for proper brain development and function. Therefore, modifications in normal levels of T3 and T4 or impaired activity of the gland itself contribute to a wide range of central nervous system alterations.

Experimental models suggest that cognitive and behavioral deficits linked to developmental hypothyroidism rely mainly on hippocampal changes that can persist throughout a person’s life.

What’s more, Rivas and his colleague also showed that maternal hypothyroidism and even mild hypothyroxinemia during pregnancy is potentially harmful to a child’s neurodevelopment[ii]. Hypothyroxinemia refers to the presence of free thyroxine (fT4) value below the 2.5th percentile with a TSH level in a normal range during pregnancy.

While hypothyroidism is strongly linked with weak memory and decreased cognitive abilities, the underlying mechanisms are still not fully elucidated. Many studies on this subject are ongoing while some completed research delivered an important insight into the role of hypothyroidism in weak memory.

 How hypothyroidism affects memory

As mentioned above, while weakened memory and cognitive abilities are a symptom of hypothyroidism it is not entirely clear how this actually happens. Many theories exist, and it’s safe to say a number of new ones will emerge in the future. According to Rivas and his paper mentioned above altered hippocampal neurogenesis that is observed in hypothyroid adults could contribute to behavioral and cognitive deficits linked with this condition.

Weakened memory due to hypothyroidism could be down to impairment in LTP (long-term potentiation) in the CA1 region of the hippocampus. On the flip side, the scientists who worked on this research reported that T4 replacement corrects this impairment and thereby has the potential to improve the memory of a hypothyroid patient or prevent it from weakening.

Thyroid hormones are involved in the maturation of the cholinergic system which takes part in learning and memory. As a result, some of hypothyroidism’s effects on memory could also be down to impairment in the cholinergic system[iii] too, according to Smith et al. Cholinergic system relies on the neurotransmitter acetylcholine which has a number of roles including encoding and retrieval of memories. Therefore, it comes as no wonder why impairment of cholinergic system due to thyroid inactivity could also lead to problems with memory.

Basically, hypothyroidism affects memory because thyroid hormones play a role in brain areas that are crucial for our memories and cognitive skills. When production of these hormones slows down, this leads to impairments in cholinergic system and hypothalamus, and we experience these effects via brain fog in most cases.

Your brain works hard 24/7, and it needs a lot of energy to do its job correctly. That being said, people with hypothyroidism experience problems such as lack of energy and slow metabolism. Depleted energy levels have an impact on your brain, i.e., they decrease mental sharpness and your ability to recall information, focus, solve problems, among other things.

Decreased mental clarity or brain fog is a common effect that many hypothyroid patients experience and it has a lot to do with the nature of hypothyroidism itself. Of course, lack of energy is one out of many mechanisms by which hypothyroidism influences memory.

Hypothyroidism a risk factor for cognitive impairment

Bégin et al. explained that subclinical hypothyroidism could be a predisposing factor for cognitive impairment. Their review showed that patients who had subclinical hypothyroidism for 16 ± 6.2 months manifested impaired cognitive activity compared to healthy subjects. Young adult patients with subclinical hypothyroidism experience mild dysfunction in memory, learning, and selective attention.

Clinical hypothyroidism also exhibits negative effects on cognitive abilities. Common problems that men and women with clinical hypothyroidism experience on this front include decreased attention, general cognition, psychomotor speed, memory, and learning[iv]. Psychological studies such as the research carried out by Dratman et al. found that T4 has a major impact on cognitive functioning. Your brain maintains levels of both T3 and T4 within a narrow range even when the latter starts fluctuating.

Even small, seemingly insignificant alterations in levels of T4 in the brain could have major consequences on cognitive abilities[v]. In hypothyroidism concentration of T4 lowers thus causing problems with memory and other functions.

Speaking of cognitive impairment and hypothyroidism, it’s important to mention that studies have confirmed both low, and high TSH could increase the risk of Alzheimer’s disease in women, but not in men[vi]. Alzheimer’s disease, the most common type of dementia, is indicated by severe cognitive decline, behavioral problems, and decreased social skills that make an individual unable to function alone as the disease progresses.

Hypothyroidism decreases hippocampus

The impact of hypothyroidism on hippocampus was briefly mentioned above. As you had the opportunity to see, hypothyroidism can contribute to weakened memory by impairing hippocampal neurogenesis and acting on a specific area of the hippocampus. Hypothyroidism and its effects on the hippocampus are complex and a subject of many ongoing studies, but it’s important to discuss it a little bit further.

What is the hippocampus?

Hippocampus is an area of the brain located in the inner folds of the bottom middle section of the brain called the temporal lobe. This part of the brain belongs to the limbic system which is linked to reactions such as reacting and feeling. The proper function of the hippocampus is vital for functions such as processing and retrieving declarative and spatial relationship memories. Declarative memories deal with events and facts while spatial relationship memories are involved in routes or pathways.

For many years it was hypothesized that cognitive problems in hypothyroid patients could be due to the reduced volume of the hippocampus. Cooke et al. carried out a study whose primary objective was to prove the accuracy of that thesis, i.e., to establish whether hippocampal volume was reduced in hypothyroid patients. For the purpose of the study, they enrolled 11 untreated hypothyroid adults and nine age-matched healthy controls.

Subjects underwent brain scans that determined the volume of their hippocampus. Results showed that hypothyroid patients have a significant reduction in hippocampal volume compared to their healthy counterparts. Scientists concluded that hypothyroidism induces structural changes in the brain[vii]. Reduced hippocampal volume could also explain problems with memory that hypothyroid patients experience.

Hypothyroidism treatment and memory

Hypothyroidism is usually managed with levothyroxine which makes up for the lower T4 levels in the body. The treatment has a goal to balance hormones and thereby manage symptoms associated with hypothyroidism. It turns out, and levothyroxine can help patients avoid problems with memory and other cognitive abilities.

Miller et al. carried out a study to assess the effects of thyroid replacement therapy on cognitive function in patients suffering from untreated hypothyroidism. After three months of treatment, hypothyroid patients experienced a significant verbal memory retrieval.

Scientists concluded that specific memory retrieval deficits linked with hypothyroidism could resolve after treatment with levothyroxine[viii].

Alzoubi et al. also had similar findings; their study discovered that treatment with levothyroxine is able to reverse “hypothyroidism-induced impairment of hippocampus-dependent cognition.” At the same time, levothyroxine treatment can improve LTP by “restoring levels of signaling molecules important for these processes”[ix].

As you can see, studies have confirmed the benefits of levothyroxine for improvement of memory and cognitive abilities in hypothyroid patients. This only emphasizes the importance of proactive attitude and sticking to the doctor-recommended treatment.

How to improve memory

Dealing with poor memory can be quite frustrating. You’re unable to do your job properly, struggle to recall information, and as a result, you feel stressed out. It’s needless to mention you can’t concentrate on the task at hand, solve problems adequately, perform decision-making skills, and so much more.

Treatment with levothyroxine improves cognitive functions in hypothyroid patients, but there are many other things you can do to improve your memory. Combine the following approaches with hypothyroidism treatment for sharper memory and stronger brain:

  • Consult your doctor – while problems with memory and brain fog are common symptoms of hypothyroidism; it’s not uncommon for patients to feel reluctant to discuss it with their doctor. Your physician will provide useful advice on things you can do to improve memory
  • Stay active – regular physical activity is vital for brain and its function. Plus, exercise is important for hypothyroidism management too. Hypothyroid patients tend to struggle with weight gain and exercise can help you slim down and keep your weight in a healthy range. The choice of physical activity depends on you. Ideally, that should be a type of activity you really like because that way you are more likely to stick to it
  • Manage stress – hypothyroidism can increase stress which also exhibits a negative impact on your memory. Unresolved stress causes numerous problems in our body, and it’s important to be proactive rather than ignore it or wait for stress to go away on its own. Stress management will keep you more focused on the task at hand, and it makes a recall of memories easier. Do something you find relaxing such as taking deep breaths, meditation, yoga, writing, anything basically
  • Get enough sleep – when you sleep your brain still works hard to store information properly so you can remember and recall them. Getting enough good night’s rest is crucial for brain function and cognitive abilities. It’s not just about getting 7 to 9 hours of sleep, and you need to establish a regular sleep schedule as well. Make sure your bedtime is same every night, and you wake up every morning at the same time as well
  • Challenge your brain – the brain is like muscles in your body; in order to become stronger, it needs to face a challenge. The same way you do physical exercises for a stronger body, you also need to do some brain exercises to strengthen its power. Options are endless here; anything that challenges your mind is considered a good brain exercise. You can read, write, learn a new language, take up a new hobby, sign up for a class, travel, socialize, do crosswords, puzzles, or Sudoku

Conclusion

Hypothyroidism is strongly associated with weak memory and mechanisms that underlying this effect are numerous. Hypothyroid patients experience structural changes in their brain and impairments in the cholinergic system.

Thyroid hormones play a role in brain function so decreased production of T4 could also contribute to memory problems. Levothyroxine treatment proves to be effective for reversing memory and cognitive functions in adults with hypothyroidism.

References

[i] Hypothyroidism (underactive thyroid), National Institute of Diabetes and Digestive and Kidney Diseases https://www.niddk.nih.gov/health-information/endocrine-diseases/hypothyroidism

[ii] Rivas M, Naranjo JR. Thyroid hormones, learning, and memory. Genes, Brain, and Behavior 2007 Jun;6 Suppl 1:40-4. Doi: 10.1111/j.1601-183X.2007.00321.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1601-183X.2007.00321.x

[iii] Smith JW, Evans AT, Costall B, Smythe JW. Thyroid hormones, brain function, and cognition: a brief review. Neuroscience and Behavioral Reviews 2002 Jan;26(1):45-60 https://www.ncbi.nlm.nih.gov/pubmed/11835983

[iv] Bégin ME, Langlois MF, Lorrain D, Cunnane SC. Thyroid Function and Cognition during Aging. Current Gerontology and Geriatrics Research. 2008;2008:474868. doi:10.1155/2008/474868. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2671998/

[v] Dratman MB, Crutchfield FL, Gordon JT, et al. Iodothyronine homeostasis in rat brain during hypo- and hyperthyroidism. American Journal of Physiology 1983 Aug;245(2):185-93. Doi: 10.1152/ajpendo.1983.245.2.E185 https://www.ncbi.nlm.nih.gov/pubmed/6881331/

[vi] Tan ZS, Beiser A, Vasan RS, et al. Thyroid Function and the Risk of Alzheimer’s Disease: The Framingham Study. Archives of internal medicine. 2008;168(14):1514-1520. doi:10.1001/archinte.168.14.1514. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2694610/

[vii] Cooke GE, Mullally S, Correia N, et al. Hippocampal volume is decreased in adults with hypothyroidism. Thyroid 2014 Mar;24(3):433-40. Doi: 10.1089/thy.2013.0058 https://www.ncbi.nlm.nih.gov/pubmed/24205791

[viii] Miller KJ, Parsons TD, Whybrow PC, et al. Memory improvement with treatment of hypothyroidism. International Journal of Neuroscience 2006 Aug;116(8):895-906. Doi: 10.1080/00207450600550154 https://www.ncbi.nlm.nih.gov/pubmed/16861154

[ix] Alzoubi KH, Gerges NZ, Aleisa AM, et al. Levothyroxine restores hypothyroidism-induced impairment of hippocampus-dependent learning and memory: behavioral, electrophysiological, and molecular studies. Hippocampus 2009 Jan;19(1):66-78. Doi: 10.1002/hipo.20476 https://onlinelibrary.wiley.com/doi/abs/10.1002/hipo.20476

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