Thyroid Function and Brain

Since the first diagnosis of hypothyroidism, various mental health issues, namely depression, dementia, and anxiety, have been associated with low thyroid function. Thyroid hormone is essential for the formation of the fetal brain. Pregnant women need double the amount of iodine to ensure their babies have a healthy cognitive function. The thyroid hormone not only builds the brain but also maintains and regenerates the adult brain. Thyroid hormones regulate brain neuroplasticity and brain-derived neurotrophic factor. Brain-derived neurotrophic factor, known as BDNF, keeps neurons healthy and promotes the growth of new ones. Hypothyroidism can turn a perfectly healthy brain into an incredibly shrinking brain. For over 200 years, Western medicine has noted the mental changes in people with thyroid problems. Since 1993, this has existed as a new medical field called psychothyroidology, but it's not something that comes up in search engines, and not many clinicians know about it.In 1786, Caleb Parry, a British physician, noticed a young woman was traumatized after falling out of her wheelchair while it was going downhill. She wasn't hurt, but two weeks later, she developed goiter and became suicidal. In 1874, William Gull published an article showing how insufficient thyroid hormone can cause severe symptoms in middle-aged women. Remarking that although patients' intellect was the same, they became depressed and apathetic. In 1891, the trance-like state that afflicted Dr. Ord's hypothyroid patients came with hallucinations and psychotic delusions, a condition he named myxedema madness. While some didn't have classic signs of hypothyroidism—swelling in the face and cold body temperature —they recovered from their psychoses when they were treated for hypothyroidism. George Crile, the American surgeon and thyroid expert who dominated thyroid studies in the US from the 1920s to the 1950s, described his hypothyroid patients as having sleep disturbances, restlessness, weakness, fatigue, and lack of concentration. His younger hypothyroid patients seemed agitated, but the older patients were depressed.

Hypothyroidism can cause reduced cognition and slowed motor function—slowed everything—so a slowed down brain. Thoughts don't come; words don't come; memories don't come. But that is the last stage. Before that, the brain is trying desperately to balance an imbalance. This is why the symptoms are so varied. In hyperthyroidism, the thyroid overproduces because antibodies attack it or it senses it won't make hormones much longer. In hypothyroidism, the thyroid cannot produce enough hormones because crucial nutrients are lacking or there is a hormone conversion problem. To make it even more confusing, a person can veer between hypo and hyper throughout the day, weeks, months, and years. Psychiatric conditions, such as depression, anxiety, mania, panic, Alzheimer's, dementia, eating disorders, schizophrenia, and suicide ideation, have been associated with low or irregular thyroid function.

Congenital iodine deficiency syndrome used to called cretinism and it was common in areas where iodine was deficient. It causes neonatal and childhood brain damage as well as delayed bone and endocrine development. Evelyn Man’s research from the 1040s illustrated that iodine deficiency during pregnancy caused learning and developmental disabilities in children. Sufficient iodine is crucial for adequate levels of thyroid homone during pregnancy. Maternal thyroid hormone builds the fetal brain. Maternal hypothyroidism puts children at risk for autism, Down’s syndrome, cerebral palsy, seizures, and low IQ.

Thyroid hormone regulates cellular function in all tissues and regularly regulars it in the brain. The brain needs more T3 than any other tissue. T3 receptors are found in neurons, mainly in the hippocampus and amygdala, the brain regions governing mood, memory, and learning. Even mild hypothyroidism, if sustained for a long time, may cause irreversible damage to cognitive function because it alters the volume of the brain. In hypothyroidism, the brain shrinks.

In 1972, a study measured the brain waves of patients with subclinical hypothyroidism and agitated depression. All of the subjects had slow waves, common in epilepsy, Alzheimer's, and non-convulsive seizures. The brain is an electrochemical organ. The brain generates beta waves when aroused and actively engaged in mental activities. When we sleep dreamless, our brain makes delta waves. You will be in a trance if you're awake with delta waves in the brain. Not the good meditative kind, but your brain doesn't work kind. That is what the hypothyroid brain can feel like. High TSH is high, but free T4 and free T3 levels within the medical range, a condition called subclinical hypothyroidism, contribute to the rapid cycling of bipolar mood disorder. In one study of people with hypothyroidism, cerebral blood flow was reduced by 38%.

Depression seems to be significantly associated with altered thyroid function. Up to 80% of people diagnosed with hypothyroidism are women, and women diagnosed with rapid cycling bipolar disorder often also have low thyroid function. A 1983 study demonstrated that 92% of the people with rapid cycling bipolar disorder had hypothyroidism.In elderly patients, hypothyroidism is often mistaken for dementia. Both undiagnosed hypothyroidism and hyperthyroidism increase the risk of Alzheimer's disease, again, especially in women. 25% of depressed patients have a blunted TSH response, so their hypothalamus is calling the pituitary and telling it to tell the thyroid to make more hormones. Still, the pituitary gland doesn't answer the phone, and the thyroid doesn't produce needed hormones.

There is something called Hashimoto's encephalopathy, and guess what? It is more prevalent in women. With Hashimoto's encephalopathy, they have high thyroid antibodies and psychiatric symptoms, such as aggression, hallucinations, dementia, headaches, trouble concentrating, and even coma. In one study, 27% had strokes, 38% psychosis, 66% seizures, and abnormal brain waves. Researchers theorize that, in this case, antibodies are targeting brain tissue. Any tissue can be targeted by autoimmunity. That's the problem with autoimmunity. Hashimoto’s is not addressed with treatment for hypothyroidism because doctors do not think antibody levels can go into remission, and no tissue is safe. In these cases, as hypothyroidism gets worse, symptoms worsen. However, symptoms go away if they are treated for hypothyroidism. 47% of women with postpartum thyroiditis had depression six weeks after giving birth. Many women are never diagnosed or diagnosed too late.

As with any physiological issue, stress can make it worse. Both thyroid and irregular adrenal function cause depression. When stress is chronic, we first have a nervous system response, then an adrenal response, and then, later, but inevitably, a thyroid response. Stress raises cortisol levels until we run out of cortisol.

Abnormal thyroid function causes chronic stress. St dies have found that patients with bipolar disorder have an overactive stress system. Those with depression initially have cortisol levels twice as high as healthy controls. The longer they have high cortisol, the faster they exhaust their ability to make it, leading to deeper depression. High epinephrine or adrenaline levels make T3 levels crash. High cortisol inhibits TSH and lowers the conversion of T4 to T3. Hypothyroidism initially increases cortisol levels due to decreased cortisol clearance in the liver, which will eventually lead to low cortisol. Finally, the thyroid hormone increases GABA, which is a calming neurotransmitter. It's the stuff you want when you take Ambien and Benzos to try to relax. Unfortunately, both damage the thyroid and the adrenal function. It can be a vicious circle that goes round and round.

Psychiatrists can't measure thyroid hormone levels in the brain. Modern medicine cannot reach a diagnosis without measurements, even in the presence of many symptoms. Because it is acutely sensitive to thyroid hormone levels, the brain is locked up tight by the blood-brain barrier.

Brain levels are more tightly controlled than any other tissue. T3 is so important that the brain has extra T4 to convert into T3 if more is needed. Both T4 and T3 decide the rate at which brain neurons regenerate. The problem is that 80% of the T3 in the brain is converted from deiodinase 2, which isn't sensitive to TSH. Your thyroid won't make more hormones when your brain needs it. As a result, your TSH level will not indicate if your brain needs more thyroid hormone.

T4 can convert into T3 in the brain, and T4 and T3 cross the blood-brain barrier. T3 levels balance out faster in peripheral tissues, kidneys, and liver, where a different enzyme, deiodinase 1, converts T4 to T3. Because the brain has only 20% of the thyroid hormone levels in circulation, if your T3 level goes up on your blood test, the measurement reflects levels in all tissues except the brain. Other tissues get what they need to function optimally. If levels are low in the rest of the body, the brain won't get thyroid hormone until the rest of the body runs out. Studies in psychothyroidology demonstrated people's brains seem to feel better at high thyroid hormone levels.

How can you improve thyroid function in the brain? Few people know the impact diet has on their thyroid. It would help if you had the nutrients for thyroid function— iodine, zinc, magnesium, and selenium. You also need the amino acid tyrosine, the most bioavailable source of animal protein. There is tyrosine in plant foods, yet those sources all have anti-nutrients, which interfere with thyroid function. You must also ensure the adrenals have their necessary nutrients —cholesterol and B vitamins, best sourced from animal foods. Then, you must remove inflammation because nothing works well in the presence of inflammation. Inflammation makes MRNA proteins unravel, which causes autoimmunity. The carnivore diet reduces inflammation.

Since T4 to T3 conversion is even more critical in the brain, you need adequate selenocysteine, a rare amino acid with selenium attached. The three enzymes that convert thyroid hormone— deiodinase 1, deiodinase 2, and deiodinase 3—are made of selenocysteine. You need plenty of deiodinase 2 in the brain. The selenium has to be bioavailable for it to be metabolized into selenocysteine. People claim plant foods, such as Brazil nuts and broccoli, have plenty of selenium, but plant-sourced selenium is not bioavailable. Tissues don't retain it. The same goes for selenium supplements. The most bioavailable sources of selenium are egg yolks and beef.