An overactive thyroid can cause male breast growth, according to Healthline. Other symptoms that are not gender specific include weight loss, hair loss, rapid heart rate, an enlarged neck and frequent bowel movements. Patients may feel nervous or restless, have hand tremors, experience higher blood pressure or increased appetite. If hyperthyroidism is a symptom of Graves disease, the eyes may appear to bulge from their sockets.
Hyperthyroidism may also cause atrial fibrillation, notes Healthline. Symptoms of atrial fibrillation include shortness of breath, a racing heart, dizziness or loss of consciousness. Atrial fibrillation occurs when the top two chambers of the heart contract rapidly and do not effectively circulate blood to the lower two chambers of the heart, according to the National Heart, Lung and Blood Institute. Although someone may not notice he has atrial fibrillation, this heart problem increases the risk of stroke, heart failure and chest pain.
Doctors can diagnose hyperthyroidism through blood tests that check T4, TSH, triglyceride and cholesterol levels, according to Healthline. They may also use ultrasound to determine if the patient has an enlarged thyroid or has a growth on the thyroid gland. A patient may undergo a computed tomography scan or magnetic resonance imaging to look for a pituitary gland tumor as well.