Hyperthyroidism is a medical condition where the thyroid gland produces an excessive amount of thyroid hormone. Nearly every process in an individual's body is sped up when more thyroid hormone is produced. Common symptoms include frequent nervousness, heat intolerance, fast heart rate, problems sleeping, excessive hunger, and weight loss. However, untreated hyperthyroidism induces more havoc on the heart muscle and cardiovascular system than just elevating the heart rate. An excess of thyroid hormone causes the heart muscle to work harder than it would otherwise.
An overstimulated thyroid gland can produce marked disturbances in a patient's heart rhythm. Overworking the heart can also create issues with how the valves work. Valve leaflets can become worn out and too thin, or they can become too stiff. Both problems with the valve leaflets can produce a heart murmur because the blood cannot flow through them properly. Blood can flow backward in the wrong direction, producing a heart murmur.