The Thyroid Gland Can Have Significant Impact on Your Brain and Mental Health
The Thyroid Gland Can Have Significant Impact on Your Brain and Mental Health
posted: Nov. 10, 2025
When Nancy Hord Patterson felt her heart pounding through her chest while driving home in Jacksonville, FL, one day, she knew something was wrong. But Patterson, 44 at the time, didn't know she was starting a decades-long journey that would shape not only her life but also the lives of countless others.
“I saw my blouse bouncing with every heartbeat,” she recalls of that day in 1987. “I felt like I was losing control.”
Patterson had just earned her doctorate in counselor education, focusing on stress management, and yet here her body was sounding an alarm she could not explain. “I couldn't think of any stress,” she says. “But my heart was racing.”
Her first stop was to see a cardiologist, and while tests showed nothing wrong with her heart, she passed out during a stress test on a treadmill. She next saw an endocrinologist, who noted that a significant marker—her thyroid-stimulating hormone (TSH) levels—were abnormal. More tests and referrals followed, and Patterson ultimately was diagnosed with hyperthyroidism, caused by Graves’ disease, an autoimmune disorder that sends the body's metabolism into overdrive.
The thyroid may be small—just about 2 inches long—but it has a significant influence on brain function and the rest of the body. Located at the base of the neck, the butterfly-shaped gland produces a hormone called T4 (thyroxine) that is converted in the bloodstream to T3 (triiodothyronine). Both hormones help regulate how the body uses energy. TSH, which the pituitary gland in the brain produces, regulates T4 production from the thyroid gland. Changes in T4 and T3 hormone levels can affect many organs, including the brain.
“The brain is highly sensitive to thyroid hormone levels,” says Chien-Hsiang Weng, MD, MPH, a clinical associate professor in the department of family medicine at the Warren Alpert Medical School of Brown University and attending physician at Brown University Health. “Even mild disruptions in brain metabolism and neurotransmitter systems can result in changes to mood, cognition, and mental clarity.”
Behind the Disorders
Thyroid disease affects an estimated 20 million Americans, according to the American Thyroid Association, and women are five to eight times more likely than men to be affected. People are especially at risk if they have a family history of thyroid disease, have other autoimmune conditions, take medication high in iodine, underwent surgery to the pituitary gland, or received radiation therapy to the head or neck.
Two main types of disorders exist: hypothyroidism, when the gland underproduces hormones, and hyperthyroidism, when it makes too much. Hyperthyroidism typically occurs between ages 20 and 40, whereas hypothyroidism is more common after age 60.
Both can disrupt brain function in distinct ways. Evidence shows that thyroid dysfunction can alter blood flow in the brain, which can contribute to cognitive challenges. It also is an often-overlooked contributor to neuropsychiatric symptoms, especially in aging adults, according to Dr. Weng.
Hypothyroidism is most often associated with depressive symptoms, such as fatigue, low mood, and decreased motivation, says Matthew Ettleson, MD, an endocrinologist at the University of Chicago. Many patients experience subtle cognitive changes, such as “trouble finding the right words, feeling slower with day-to-day tasks—even something as small as reading a receipt and processing it,” he adds.
Symptoms of hypothyroidism may emerge gradually and can be mistaken for signs of aging, depression, or stress. “That's why diagnosis can be delayed,” Dr. Weng says. “We need to raise awareness that subtle neurologic symptoms may actually stem from the thyroid.”
Hyperthyroidism, on the other hand, commonly caused by Graves’ disease, presents more like anxiety than depression, speeding up brain activity in ways that can feel jarring: irritability, restlessness, insomnia, mood swings, and difficulty with attention and memory. These patients may experience what Dr. Ettleson calls “non-productive fatigue—burning through energy quickly but not feeling recharged.”
After her initial diagnosis of hyperthyroidism and Graves’ disease, Patterson quickly learned that thyroid disease can produce psychiatric-like symptoms, including confusion, irritability, memory lapses, insomnia, and even mania or depression. “I've had doctors tell me my behavior was ‘crazy’ when my thyroid levels were off,” she says. “But it wasn't depression. It wasn't anxiety. It was my thyroid.”
Despite taking standard medications for hyperthyroidism and Graves’ disease, such as radioactive iodine, Patterson's symptoms didn't stop at a racing heartbeat or mood swings. A “funny” sensation in her eyes turned out to be thyroid eye disease, a serious inflammatory condition that can cause bulging eyes, double vision, and, in rare cases, vision loss. “I had to tape my eyes shut to sleep,” Patterson says. “They weren't closing on their own.”
Her vision became distorted, and swelling and tissue inflammation made daily activities nearly impossible. She did everything her doctor recommended: steroids, ice packs, diuretics, raising the head of her bed, and strict sodium restrictions. Eventually, Patterson underwent a series of eye surgeries.
Patients who develop thyroid eye disease also may be prescribed teprotumumab, a targeted insulin growth factor 1 receptor (IGF1R) inhibitor. The drug can be expensive, however: for a patient weighing about 165 pounds, one infusion costs about $45,000, and eight infusions about $360,000, according to a 2024 report in the Journal of Personalized Medicine.
Treatment Options
Treatment for thyroid disease generally is designed to normalize thyroid hormone levels, but clinicians must calibrate these therapies precisely because both undertreatment and overtreatment carry risks.
For hypothyroidism, the standard therapy is levothyroxine, a synthetic form of the T4 hormone. If their dose is too low, patients may stay in a hypothyroid state and continue to experience brain fog or depression, Dr. Weng says, and if it's too high, “they may swing into a [drug-induced] hyperthyroid state, which can worsen anxiety or cardiovascular risk, especially in older adults.”
Treatment for hyperthyroidism—such as the radioactive iodine Patterson used as well as antithyroid drugs and surgery—can be effective but require close follow-up. Many patients eventually develop hypothyroidism after radioactive iodine and surgery and need lifelong hormone replacement. While radioactive iodine has not been directly tied to cognitive effects, the hypothyroidism it can cause can then impact a patient's brain health if not carefully managed, Dr. Ettleson notes.
Treating thyroid disease is critical for brain health, and in most cases, normalizing thyroid hormone levels leads to improvements in brain function. “Most patients experience at least some relief in terms of memory, focus, and mood,” Dr. Ettleson says. “But … a significant number of patients tell me they never feel fully ‘back to normal.’”
Dr. Ettleson emphasizes that this isn't because the medication causes cognitive or mental health issues. More likely, the treatment is only partially effective for some patients. “If someone doesn't convert T4 to T3 efficiently in the brain, they might still feel off, even if their labs look normal,” he says.
Promising Research
Recent research has shed light on the thyroid-brain connection and associated neuropsychiatric challenges, including a population-based study involving Dr. Weng. Published in Neurology in 2022, the study found that older adults with treated hypothyroidism had more than triple the odds of being diagnosed with dementia compared to those without thyroid disease. While the study didn't prove that the treatment caused harm, it raised important questions.
“It's possible that needing treatment reflects more severe or long-standing thyroid dysfunction,” Dr. Weng says, and by the time treatment begins, the patient's brain may already be irreversibly affected.
The study also supports growing evidence that untreated or undertreated hypothyroidism in older adults may significantly raise the risk of dementia, highlighting the importance of early diagnosis and appropriate management of thyroid disease to help protect long-term brain health.
Meanwhile, a study published in The Journal of Endocrinology & Metabolismin 2022 suggests that thyroid hormone levels that are too high or low may reduce blood flow in the brain, which over time could increase the risk of stroke, cognitive decline, or dementia. Crucially, this circulation issue might be modifiable; using medication and lifestyle interventions to keep a patient's thyroid hormone levels in a healthy range might support better brain health as they age.
The Power of Self-Advocacy
In addition to adhering to medication, people with thyroid disease may want to include self-advocacy in their toolkit. In this regard, Patterson has blazed a noteworthy trail. After her first eye surgery, she asked a simple question: “Where are the support groups?”
“There weren't any,” Patterson says. “So I said, ‘Well, there will be.’”
With the professional backing of her endocrinologist, she launched what became the Graves’ Disease & Thyroid Foundation. The group began by providing information, support groups, and advocacy for patients with Graves’ disease and thyroid eye disease at a time when few resources existed.
The foundation has grown to influence research and clinical care. For more than 30 years, Patterson has stayed in touch with scientists from the University of California, Los Angeles, who had reached out to her while studying what became the first U.S. Food and Drug Administration-approved treatment for thyroid eye disease. She advances the foundation's mission to educate doctors and patients alike on the specific, often invisible struggles patients face. And she emphasizes how gender bias can delay diagnosis for many women.
“Doctors assume women's cognitive or mental health issues are due to stress or hormones or that we're just emotional,” Patterson notes. “By the time the doctor runs out of excuses, the thyroid is finally tested.”
But she's encouraged that some medical schools now teach courses on how to listen to patients. She urges people with thyroid symptoms to communicate their experiences effectively: “Don't just say, ‘I feel terrible.’ Say, ‘I'm only sleeping two hours a night.’ Be specific. Keep a journal. Make them listen.”
Patterson, now a clinical specialist in psychiatric/mental health nursing, often encounters patients with thyroid disease who think they're losing their minds. “They'll say, ‘I don't know what's wrong with me.’ I tell them, ‘These are psychiatric symptoms, yes, but they don't come from your emotions. They come from your hormones. It's like putting a Ferrari in park and stomping on the gas.”
When Nancy Hord Patterson felt her heart pounding through her chest while driving home in Jacksonville, FL, one day, she knew something was wrong. But Patterson, 44 at the time, didn't know she was starting a decades-long journey that would shape not only her life but also the lives of countless others.
“I saw my blouse bouncing with every heartbeat,” she recalls of that day in 1987. “I felt like I was losing control.”
Patterson had just earned her doctorate in counselor education, focusing on stress management, and yet here her body was sounding an alarm she could not explain. “I couldn't think of any stress,” she says. “But my heart was racing.”
Her first stop was to see a cardiologist, and while tests showed nothing wrong with her heart, she passed out during a stress test on a treadmill. She next saw an endocrinologist, who noted that a significant marker—her thyroid-stimulating hormone (TSH) levels—were abnormal. More tests and referrals followed, and Patterson ultimately was diagnosed with hyperthyroidism, caused by Graves’ disease, an autoimmune disorder that sends the body's metabolism into overdrive.
The thyroid may be small—just about 2 inches long—but it has a significant influence on brain function and the rest of the body. Located at the base of the neck, the butterfly-shaped gland produces a hormone called T4 (thyroxine) that is converted in the bloodstream to T3 (triiodothyronine). Both hormones help regulate how the body uses energy. TSH, which the pituitary gland in the brain produces, regulates T4 production from the thyroid gland. Changes in T4 and T3 hormone levels can affect many organs, including the brain.
“The brain is highly sensitive to thyroid hormone levels,” says Chien-Hsiang Weng, MD, MPH, a clinical associate professor in the department of family medicine at the Warren Alpert Medical School of Brown University and attending physician at Brown University Health. “Even mild disruptions in brain metabolism and neurotransmitter systems can result in changes to mood, cognition, and mental clarity.”
Behind the Disorders
Thyroid disease affects an estimated 20 million Americans, according to the American Thyroid Association, and women are five to eight times more likely than men to be affected. People are especially at risk if they have a family history of thyroid disease, have other autoimmune conditions, take medication high in iodine, underwent surgery to the pituitary gland, or received radiation therapy to the head or neck.
Two main types of disorders exist: hypothyroidism, when the gland underproduces hormones, and hyperthyroidism, when it makes too much. Hyperthyroidism typically occurs between ages 20 and 40, whereas hypothyroidism is more common after age 60.
Both can disrupt brain function in distinct ways. Evidence shows that thyroid dysfunction can alter blood flow in the brain, which can contribute to cognitive challenges. It also is an often-overlooked contributor to neuropsychiatric symptoms, especially in aging adults, according to Dr. Weng.
Hypothyroidism is most often associated with depressive symptoms, such as fatigue, low mood, and decreased motivation, says Matthew Ettleson, MD, an endocrinologist at the University of Chicago. Many patients experience subtle cognitive changes, such as “trouble finding the right words, feeling slower with day-to-day tasks—even something as small as reading a receipt and processing it,” he adds.
Symptoms of hypothyroidism may emerge gradually and can be mistaken for signs of aging, depression, or stress. “That's why diagnosis can be delayed,” Dr. Weng says. “We need to raise awareness that subtle neurologic symptoms may actually stem from the thyroid.”
Hyperthyroidism, on the other hand, commonly caused by Graves’ disease, presents more like anxiety than depression, speeding up brain activity in ways that can feel jarring: irritability, restlessness, insomnia, mood swings, and difficulty with attention and memory. These patients may experience what Dr. Ettleson calls “non-productive fatigue—burning through energy quickly but not feeling recharged.”
After her initial diagnosis of hyperthyroidism and Graves’ disease, Patterson quickly learned that thyroid disease can produce psychiatric-like symptoms, including confusion, irritability, memory lapses, insomnia, and even mania or depression. “I've had doctors tell me my behavior was ‘crazy’ when my thyroid levels were off,” she says. “But it wasn't depression. It wasn't anxiety. It was my thyroid.”
Despite taking standard medications for hyperthyroidism and Graves’ disease, such as radioactive iodine, Patterson's symptoms didn't stop at a racing heartbeat or mood swings. A “funny” sensation in her eyes turned out to be thyroid eye disease, a serious inflammatory condition that can cause bulging eyes, double vision, and, in rare cases, vision loss. “I had to tape my eyes shut to sleep,” Patterson says. “They weren't closing on their own.”
Her vision became distorted, and swelling and tissue inflammation made daily activities nearly impossible. She did everything her doctor recommended: steroids, ice packs, diuretics, raising the head of her bed, and strict sodium restrictions. Eventually, Patterson underwent a series of eye surgeries.
Patients who develop thyroid eye disease also may be prescribed teprotumumab, a targeted insulin growth factor 1 receptor (IGF1R) inhibitor. The drug can be expensive, however: for a patient weighing about 165 pounds, one infusion costs about $45,000, and eight infusions about $360,000, according to a 2024 report in the Journal of Personalized Medicine.
Treatment Options
Treatment for thyroid disease generally is designed to normalize thyroid hormone levels, but clinicians must calibrate these therapies precisely because both undertreatment and overtreatment carry risks.
For hypothyroidism, the standard therapy is levothyroxine, a synthetic form of the T4 hormone. If their dose is too low, patients may stay in a hypothyroid state and continue to experience brain fog or depression, Dr. Weng says, and if it's too high, “they may swing into a [drug-induced] hyperthyroid state, which can worsen anxiety or cardiovascular risk, especially in older adults.”
Treatment for hyperthyroidism—such as the radioactive iodine Patterson used as well as antithyroid drugs and surgery—can be effective but require close follow-up. Many patients eventually develop hypothyroidism after radioactive iodine and surgery and need lifelong hormone replacement. While radioactive iodine has not been directly tied to cognitive effects, the hypothyroidism it can cause can then impact a patient's brain health if not carefully managed, Dr. Ettleson notes.
Treating thyroid disease is critical for brain health, and in most cases, normalizing thyroid hormone levels leads to improvements in brain function. “Most patients experience at least some relief in terms of memory, focus, and mood,” Dr. Ettleson says. “But … a significant number of patients tell me they never feel fully ‘back to normal.’”
Dr. Ettleson emphasizes that this isn't because the medication causes cognitive or mental health issues. More likely, the treatment is only partially effective for some patients. “If someone doesn't convert T4 to T3 efficiently in the brain, they might still feel off, even if their labs look normal,” he says.
Promising Research
Recent research has shed light on the thyroid-brain connection and associated neuropsychiatric challenges, including a population-based study involving Dr. Weng. Published in Neurology in 2022, the study found that older adults with treated hypothyroidism had more than triple the odds of being diagnosed with dementia compared to those without thyroid disease. While the study didn't prove that the treatment caused harm, it raised important questions.
“It's possible that needing treatment reflects more severe or long-standing thyroid dysfunction,” Dr. Weng says, and by the time treatment begins, the patient's brain may already be irreversibly affected.
The study also supports growing evidence that untreated or undertreated hypothyroidism in older adults may significantly raise the risk of dementia, highlighting the importance of early diagnosis and appropriate management of thyroid disease to help protect long-term brain health.
Meanwhile, a study published in The Journal of Endocrinology & Metabolismin 2022 suggests that thyroid hormone levels that are too high or low may reduce blood flow in the brain, which over time could increase the risk of stroke, cognitive decline, or dementia. Crucially, this circulation issue might be modifiable; using medication and lifestyle interventions to keep a patient's thyroid hormone levels in a healthy range might support better brain health as they age.
The Power of Self-Advocacy
In addition to adhering to medication, people with thyroid disease may want to include self-advocacy in their toolkit. In this regard, Patterson has blazed a noteworthy trail. After her first eye surgery, she asked a simple question: “Where are the support groups?”
“There weren't any,” Patterson says. “So I said, ‘Well, there will be.’”
With the professional backing of her endocrinologist, she launched what became the Graves’ Disease & Thyroid Foundation. The group began by providing information, support groups, and advocacy for patients with Graves’ disease and thyroid eye disease at a time when few resources existed.
The foundation has grown to influence research and clinical care. For more than 30 years, Patterson has stayed in touch with scientists from the University of California, Los Angeles, who had reached out to her while studying what became the first U.S. Food and Drug Administration-approved treatment for thyroid eye disease. She advances the foundation's mission to educate doctors and patients alike on the specific, often invisible struggles patients face. And she emphasizes how gender bias can delay diagnosis for many women.
“Doctors assume women's cognitive or mental health issues are due to stress or hormones or that we're just emotional,” Patterson notes. “By the time the doctor runs out of excuses, the thyroid is finally tested.”
But she's encouraged that some medical schools now teach courses on how to listen to patients. She urges people with thyroid symptoms to communicate their experiences effectively: “Don't just say, ‘I feel terrible.’ Say, ‘I'm only sleeping two hours a night.’ Be specific. Keep a journal. Make them listen.”
Patterson, now a clinical specialist in psychiatric/mental health nursing, often encounters patients with thyroid disease who think they're losing their minds. “They'll say, ‘I don't know what's wrong with me.’ I tell them, ‘These are psychiatric symptoms, yes, but they don't come from your emotions. They come from your hormones. It's like putting a Ferrari in park and stomping on the gas.”
