The thyroid is a small butterfly-shaped endocrine gland just above the collarbone in the front of the neck. It makes thyroid hormone, a substance that controls our metabolism — the chemical processes in the body that allow us to function every day. Hyperthyroidism occurs when the thyroid makes too much thyroid hormone. This can cause an increased metabolism, with accompanying signs and symptoms such as:

• Unintentional weight loss— even when appetite and food intake stay the same or increase

• Rapid and sometimes irregular heartbeat — more than 100 beats a minute

• Pounding of the heart — palpitations

• Nervousness — anxiety and irritability

• Tremor — usually in the hands and fingers

• Sweating— increased sensitivity to heat

• Changes in menstrual patterns and difficulty getting pregnant

• More frequent bowel movements

• Fatigue, muscle weakness

• Difficulty sleeping

• Skin thinning

• Fine, brittle hair and hair loss

Some patients may have an enlarged thyroid, known as goiter. The eyes can also become dry or red, and if severe, the eyeballs can seem to protrude and cause a distinctive “stare.” If not treated for a long time, patients can develop heart problems leading to congestive heart failure, where the heart cannot circulate enough blood throughout the body.

Patients can also get osteoporosis with weak, brittle bones that are prone to break.