Thyroid hormones are essential for brain maturation, and for brain function throughout life. In adults, thyroid disease can lead to a variety of brain disorders. Hypothyroidism (or low thyroid) for example, can cause lethargy, poor reflexes and motor coordination and is often associated with memory impairment. Hypothyroidism is also associated with bipolar affective disorder, schizophrenia, depression, and loss of cognitive functions, especially in the elderly.
On the other hand, Hyperthyroidism (or too much thyroid) causes anxiety, irritability, and increased reflex action. Both, hypothyroidism and hyperthyroidism can lead to mood disorders, dementia, confusion, and personality changes. Most of these disorders are usually reversible with proper treatment.
Stephanie Reese, PhD