The thyroid gland is a small butterfly shaped organ situated in front of the neck.

It produces a hormone called thyroxine which has important and profound effects on every important organ system in the human body including the brain, nerves, reproductive system to name a few.

It also has a wide range of effects on the heart and blood vessels.

Normal functioning of the thyroid gland is needed for normal heart rate and contraction (pumping action) and also for maintaining normal blood pressure.

Hypothyroidism- that is when the thyroid gland produces low or no thyroxine- leads to a situation of low heart rate- bradycardia- where the pulse rate can come to less than 60/minute (normal range is 60-100/minute). It can also lead to a failure of the pumping action of the heart leading to fluid accumulation in the lungs and extremities, it can lead to high blood pressure, in very severe hypothyroidism it can lead to pericardial effusion- accumulation  of fluid in the region aound the heart.

Untreated hypothyroidism can lead to worsening of artherosclerosis (cholesterol plaques in the major arteries supplying the heart and brain) and dyslipidemia (high levels of “bad cholesterol”) and increase the chances for a sudden heart attack.

A very severe state of hypothyroidism is called myxedema coma where the person needs urgent medical attention including ICU care and may need medication to maintain he normal blood pressure and contraction of the heart.

On the other hand hyperthyroidism- where there is production of thyroxine is at many times the normal level-  is characterized by a very  rapid heart rate- may go upto  140-160 beats/minute, the patient will complain of palpitations- an uncomfortable awareness of his rapidly beating heart- which may be present even at rest or during sleep. There can also be irregularity of the pulse rate- a condition called atrial fibrillation –this can lead to heart failure and sometimes even cardiac arrest as well as strokes and gangrene of the the toes/fingers because of a blood clot getting lodged in the blood vessels  supplying the brain or the peripheries. Hence it is important to pick it up and treat it fast. Hyperthyroidism can also lead to high blood pressure and cardiac failure if left untreated or inadequately treated.

Just like myxedema coma there is a condition called thyrotoxic crisis/”thyroid storm” which can be life threatening and fatal if not picked up early enough and treated appropriately –this also needs urgent admission into the ICU.

Hence any patient who comes with an usually low or high or irregular pulse rate should be examined and undergo appropriate investigations to look for an associated thyroid disorder: serum TSH and free T4 and free T3-if any abnormality is present patient’s overall outcome will improve if diagnosed early enough and treated adequately.

This webpage is edited by Dr T George Koshy.

Dr. Koshy is an Expert Endocrinologist and presently working as Assistant Professor, Endocrine Unit at Department of Medicine, Orthodox Syrian Church (MOSC) Medical College, Kolencherry, Ernakulam (Kerala), India.