The Impact of Thyroid Hormones on Your Brain

The Impact of Thyroid Hormones on Your Brain

As you age, your body undergoes various changes, including a decline in thyroid hormone levels. The thyroid gland is a butterfly-shaped organ located in the neck that produces hormones that regulate metabolism, energy levels, and other bodily functions.  Every cell in the body has receptors for thyroid hormone, so its impact is quite broad.  Low thyroid can impact your cognitive performance and is a common issue for those over 50.

Ways Your Thyroid Health Can Impact Your Brain Performance

  1. Mood: Thyroid hormone impacts the release of neurotransmitters and thus is closely tied to the function of neurotransmitters such as serotonin, dopamine, and norepinephrine, which regulate mood. Low levels of thyroid hormones can lead to depression, anxiety, and irritability.
  2. Brain development: A substantial number of genes in the brain are regulated by thyroid hormone during development and in adulthood.
  3. Maintenance of brain structure and function: The effects of thyroid hormone on the brain include regulating neurogenesis, developing synapses, formation of myelin, and differentiation and migration of neuronal and glial cells. An imbalance in thyroid hormones can lead to brain problems, including changes in brain structure and altered neurotransmitter function.

Hypothyroidism and Brain Health

Hypothyroidism (low thyroid) occurs when the thyroid gland does not produce enough thyroid hormones, or other factors interfere with having sufficient circulating thyroid hormone. The medical community defines hypothyroidism as having levels lower than are typical for your age.  However, levels decline with age and are part of the reason that elderly often have less energy and sense of well-being.  It is estimated that 4.6% of the population meets the US diagnostic criteria for hypothyroidism.  Many more experience symptoms of insufficient thyroid hormone.

When available thyroid hormone is too low, it can cause a range of symptoms, including fatigue, weight gain, depression, and memory problems. In addition, hypothyroidism has been independently linked to cognitive impairment, including memory loss and a decrease in overall mental function.

As we age, the risk of developing hypothyroidism increases. Women are 10 times more susceptible to the condition than men.  Low thyroid is often triggered by autoimmune responses where the body’s immune system attacks its own cells.  There is also an interplay between thyroid hormone and the hormones that fluctuate during the menstrual cycle.  Thyroid problems are especially common after menopause when hormone levels are changing.  Some women confuse menopause with symptoms of thyroid disorder and don’t seek treatment for the thyroid issues.  Studies show that low levels of estrogen and progesterone double the risk of dementia as well.

Another way hypothyroidism affects brain health is by causing inflammation in the brain. Inflammation can damage the neurons in the brain, leading to brain fog, memory issues, difficulty concentrating, and confusion.

Inadequate levels of free circulating thyroid hormone are a prevalent concern among individuals over age 50. However, conventional medical practitioners generally require your blood level of total thyroid to fall below the range of normal for your age to meet the criteria to diagnose this as disease. Approximately 5% of the population meets this diagnostic criteria, mostly women and those over age 60.  When your levels are outside the ‘normal’ range, MDs will prescribe a synthetic thyroid called levothyroxine.  Your MD will track your blood levels of thyroid stimulating hormone in attempts to keep your thyroid within the normal range for your age by adjusting your thyroid dose over time.  Unfortunately, levothyroxine is not the optimal approach and recent studies show ~15% of those on levothyroxine continue to feel sick despite following the standard of care recommended by the American Thyroid Association.

Functional medicine professionals, on the other hand, take into account both symptoms and blood levels and understand that many of your symptoms (brain fog, weight gain, fatigue, sluggishness) are a result of these lower thyroid levels.  Although lower thyroid is typical at older age, it is certainly far from optimal.  Functional medicine professionals will typically prescribe bioidentical thyroid that contains both T4 and T3 (the active forms of thyroid) and is similar to the thyroid produced by your body (rather than synthesized).   They also track a variety of different blood markers to adjust your dose, because some thyroid in your blood gets bound to proteins and is not active.  There is also something called reverse T3 or T4 that is also inactive.  Functional practitioners track these various forms and are aware that inactive forms of thyroid contribute to your total thyroid but do not perform the desired beneficial roles.

Treatment for Thyroid Disorders and Brain Health

This is a complicated, involved and somewhat controversial topic, but there is agreement that the brain needs sufficient hormones and nutrients to function well.  Insufficient thyroid needs to be addressed, as do other vitamin and hormone deficiencies.   

Understanding the background helps explain the complexity and variety of viewpoints.  The thyroid gland produces mostly T4 (thyroid with 4 iodines) which is converted to T3 (thyroid with 3 iodines) and reverse T3 (inactive form).  T4 and T3 can be bound to protein which makes them inactive.  Free T3 is the active version of thyroid that can enter tissues and is needed to address your symptoms.  

Most traditional physicians will generally do a blood test to assess your T4.  If your T4 level is low for your age (meets classic medical diagnostic criteria) the physician will prescribe levothyroxine, a synthetic thyroid hormone, in attempts to restore normal levels and function.  However, low thyroid may result from issues other than just insufficient T4 levels (if T4 is not converted to T3 or if T4 or T3 are not free).

Functional medicine practitioners generally test for free T3, reverse T3 and free T4, which gives a more complete picture of your thyroid function.  They are also willing to treat if you are having symptoms of low thyroid, even if you are not technically outside the range.  Low levels may be typical for your age, but they do impact your cognitive function, energy and mood.  

Ways To Support Your Thyroid Health And Brain Performance

  • Find the right MD to address your thyroid issues. A functional medicine professional who uses bioidentical hormones is more likely to be successful in improving your cognitive performance, energy, mood and quality of life.
  • Get your thyroid levels checked regularly, especially if you are older, have a family history of thyroid problems, or experience symptoms such as fatigue, weight gain, cognitive issues and/or  depression.  
  • Eat a balanced diet rich in iodine, selenium, and other nutrients that support thyroid function. Good sources include seafood, dairy products, and nuts.
  • Manage stress levels, as stress can disrupt thyroid function and lead to imbalances in hormone levels.

Key Takeaway

The thyroid plays a crucial role in maintaining your brain health.  Insufficient active circulating thyroid can have a significant impact on the brain, leading to problems with cognition, memory, and mood. It is important to be aware of the symptoms of thyroid imbalance and to seek medical treatment with a knowledgeable professional. With proper treatment and management, the impact of a thyroid imbalance on brain health can be minimized.

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