Thyroid hormones affect brain function and can influence mood, concentration, sleep, and emotional regulation.
Both excessive and insufficient thyroid hormone levels can produce psychological symptoms, although the patterns differ.
Hyperthyroidism and anxiety
People with hyperthyroidism may feel unusually nervous, restless, irritable, or emotionally overwhelmed.
They may experience racing thoughts, difficulty sleeping, or a persistent sense of being on edge.
These symptoms can resemble anxiety disorders, and in some cases thyroid dysfunction may worsen an existing mental health condition.
Hypothyroidism and low mood
People with hypothyroidism may experience low mood, slowed thinking, reduced motivation, difficulty concentrating, or memory problems.
Some describe feeling mentally foggy or struggling to complete tasks that previously seemed easy.
However, these symptoms are not specific to thyroid disease.
Depression, anxiety disorders, sleep disorders, medication effects, chronic illness, and life stress can produce similar experiences.
When should mood changes be investigated?
If mood or cognitive changes are persistent, significantly affect daily life, or occur alongside physical symptoms of thyroid dysfunction, discuss them with a healthcare professional.
Thyroid testing may be appropriate, but it is important not to assume that all emotional symptoms are caused by hormones.
Mental health conditions deserve assessment and treatment in their own right, whether or not thyroid dysfunction is present.
9. Changes in Bowel Habits
Thyroid hormones influence the movement of the digestive tract.
When thyroid function is reduced, intestinal movement may slow. This can lead to constipation, bloating, and less frequent bowel movements.
When thyroid hormone levels are excessive, intestinal movement may accelerate, causing more frequent bowel movements or diarrhea.
Constipation and hypothyroidism
Persistent constipation may be one of several symptoms of an underactive thyroid.
People may also experience fatigue, dry skin, cold intolerance, and weight gain.
However, constipation is common and can result from inadequate fiber intake, dehydration, reduced physical activity, medication effects, and many other causes.
Frequent bowel movements and hyperthyroidism
People with hyperthyroidism may notice more frequent bowel movements or loose stools.
This can occur alongside increased appetite, weight loss, sweating, and palpitations.
Severe or persistent diarrhea can cause dehydration and should be assessed appropriately.
When are bowel changes concerning?
Seek medical advice if bowel changes persist, occur with unexplained weight loss, or interfere with normal activities.
Blood in the stool, severe abdominal pain, black stools, or persistent vomiting requires prompt medical evaluation.
Thyroid disease is one possible explanation, but digestive symptoms should not automatically be attributed to hormonal problems.
10. Muscle Weakness, Cramps, or Joint Discomfort
Thyroid hormones help regulate muscle metabolism and normal neuromuscular function.
When hormone levels are abnormal, some people develop muscle weakness, cramps, stiffness, or discomfort.
Muscle symptoms associated with hypothyroidism
Hypothyroidism can contribute to muscle aches, stiffness, cramps, and reduced strength.
Some people notice difficulty climbing stairs, rising from a low chair, or carrying objects that previously felt manageable.
The symptoms may develop gradually and be mistaken for normal aging or reduced fitness.
Muscle symptoms associated with hyperthyroidism
Hyperthyroidism can cause muscle weakness, particularly in the muscles around the hips and shoulders.
A person may find it difficult to lift their arms overhead or stand up from a seated position.
This can occur because excessive thyroid hormone affects muscle protein metabolism and can contribute to muscle breakdown.
Joint discomfort
Some people with thyroid disorders experience joint or muscle discomfort, although these symptoms are not specific to thyroid disease.
Arthritis, vitamin deficiencies, autoimmune conditions, injuries, and medication effects may produce similar problems.
If muscle weakness is progressive or accompanied by significant pain, unexplained swelling, or other concerning symptoms, seek medical assessment.
Sudden severe weakness, especially when it affects one side of the body or occurs with difficulty speaking, requires emergency care because it may indicate a neurological emergency rather than a thyroid problem.
Why Are Women More Susceptible to Thyroid Disorders?
Thyroid disorders occur in both women and men, but several thyroid conditions are more common in women.
One important reason is the relationship between thyroid disease and autoimmunity.
Autoimmune diseases occur when the immune system mistakenly targets the body's own tissues. Women are disproportionately affected by many autoimmune conditions, although the exact reasons differ between diseases and are not completely understood.
The two most common autoimmune thyroid disorders are Hashimoto's thyroiditis and Graves' disease.
Hashimoto's thyroiditis
Hashimoto's thyroiditis is an autoimmune condition in which the immune system attacks the thyroid gland.
Over time, this can reduce the gland's ability to produce sufficient thyroid hormone, leading to hypothyroidism.
Symptoms may include fatigue, cold intolerance, constipation, dry skin, weight changes, and slowed thinking.