Lithium and Thyroid Function
People with bipolar disorder often have thyroid gland problems. Lithium treatment may also cause low thyroid levels in some people. Low thyroid function, called hypothyroidism, has been associated with rapid cycling in some people with bipolar disorder, especially women.
Because too much or too little thyroid hormone can lead to mood and energy changes, it is important to have a doctor check thyroid levels carefully. A person with bipolar disorder may need to take thyroid medication, in addition to medications for bipolar disorder, to keep thyroid levels balanced.