Thyroid is a small gland located in the neck. It modulates many vital functions of the body. The hormone the gland produces directly affects the heart and peripheral vascular system. The hormone can increase cardiac input by increasing myocardial inotropy and heart rate and dilate peripheral arteries. Deficiency of the thyroid hormone causes cardio vascular disease and aggravates many preexisting conditions.
The right amount of hormone produced helps to regulate the body’s metabolism as well as digestive function, muscle function and the normal integrity of the skin. To make it short, the thyroid has at least some effect on every organ of the body, including the heart.
Disorders of the thyroid gland can worsen existing heart problems or cause new ones and also can accelerate the underlying heart disease. Doctors usually forget to think about the thyroid when cardiac symptoms are worsening. If they don’t think about it, they will miss the same.
Disorders of the thyroid gland usually involve either not producing enough hormone called Hypothyroidism or the production of too much hormone called Hyperthyroidism. Both the types are common.
For the normal cardio vascular function thyroid hormone is very important. Therefore, when enough hormone is not present neither the heart nor the blood vessels can function normally. In Hypothyroidism the heart muscle becomes weak both in its contraction phase and also in the relaxation phase. With the result the heart cannot pump vigorously as it used to be and the amount of blood ejected in each heart beat is also reduced. Besides, as the heart muscle does not relax normally in between heart beats, a serious condition called diastolic dysfunction may result. Further, the amount of nitric oxide in the lining of the blood vessels is reduced and thereby causing them to stiffen. People with Hypothyroidism, the cardiac symptoms can be seen.
Common symptoms are:
- Poor exercise tolerance and shortness of breath
- Slow heart beat
- Diastolic Hypertension
- Worsening of heart failure
- Edema (swelling)
- Worsening of coronary artery disease
Hypothyroidism can be extremely subtle condition and often occurs without the typical textbook type symptoms doctors usually expect.
In Hyperthyroidism, as mentioned above, there is over production of the hormone. In this situation the heart muscle is ‘whipped’ like a horse and for a person with heart disease, it is like whipping a tired horse. Too much hormone increases the force of the contraction of the heart muscle and the amount of oxygen demanded by the muscle is also increased. Further more, in Hyperthyroidism, the amount of nitric oxide in the lining of blood vessels is increased making them to dilate and become less stiff.