There's a direct connection between thyroid disorder and bipolar symptoms – a bipolar thyroid disease if you will – but it has never been clearly determined what that connection is nor why the thyroid hormones can cause bipolar actions. Since hyperthyroidism mimics bipolar behavior, the symptoms for bipolar disorder and thyroid disease are similar.
Occidentally, medications for other health-related issues will interfere with thyroid function. Drugs like the beta blockers are a good example of this and they can cause a devastating domino effect on your overall health. While taking these medications, the thyroid action is misaligned and malfunctions by not producing the correct amount of hormone which can then cause symptoms of nervousness, fatigue, and irrational behavior. This behavior is often thought to be symptomatic of bipolar disorder and sometimes that is the case, however sometimes it's purely an underactive or overactive thyroid responding to the medications and thus result in a bipolar thyroid disorder. When correct testing of the thyroid is ignored and the patient is diagnosed as bipolar, the medications prescribed for bipolar often fail to work.
By treating the thyroid with natural herbal remedies and a diet related to the extreme of the malfunction, the bipolar actions often tend to disappear. The foremost natural treatment for the thyroid is the use of kelp or seaweed either as food form or supplements. The iodine content of this herbal substance will balance the hormone secretions. Seafood is also very beneficial to add to the diet because of the high iodine content. Once the thyroid is controlled, and this may be a lifelong dedication to diet, the bipolar activity may be reduced or even eliminated.