According to MedicineNet.com, the most common symptoms of a hyperactive thyroid are sweating excessively, being intolerant to heat, nervousness, agitation, tremors, increased bowel movements, weight loss, tiredness and decreased concentration. MedicineNet.com also states that the symptoms become more severe as the condition worsens.
MedicineNet.com states that a hyperactive thyroid is also known as hyperthyroidism. Due to an excessive production of thyroid hormones, patients experience a range of symptoms. As thyroid hormones are responsible for metabolic activity in the body, producing too much of them leads to weight loss despite having an increased appetite, shaking and more frequent bowel movements. Mayo Clinic notes that people with hyperthyroidism experience irregular menstrual cycles, muscle fatigue, a swelling at the base of the neck and insomnia.
According to WebMD, the symptoms of hyperthyroidism are often so subtle they mimic the signs of other illnesses. This is especially true of elderly patients, who often experience very subtle symptoms. According to Mayo Clinic, elderly patients take medications such as beta blockers that mask the signs of this condition.
WebMD states that more advanced cases experience severe symptoms, depending on what causes the hyperthyroidism. This includes the bulging eyes associated with Graves' disease, hair loss, thinning skin and a rapid heartbeat of more than 100 beats per minute. MedicineNet.com states that untreated hyperthyroidism causes a thyroid storm, which involves the patient experiencing high blood pressure, a fever and heart failure.