Side Effects of an Underactive Thyroid

The thyroid gland produces two types of hormones. These hormones called T3 and T4 affect different parts of the body, but they basically control the metabolic system. Hypothyroidism, commonly called an underactive thyroid, doesn't produce enough of one or both of these hormones.

Hypothyroidism has side effects some of which can be severe.

Heart Disease

Heart disease and any complication pertaining to it are the most serious side effects to an underactive thyroid. People who have heart disease may experience things like heart palpitations or a flip flop feeling in the chest, shortness of breath and dizziness. Heart disease is a serious condition and can be fatal.

Poor Circulation

There are a lot of causes of poor circulation and hypothyroidism is one of them. People who have poor circulation may also have heart disease. This normally affects the limbs (arms and legs) and people may notice a blue tint to their skin. Poor circulation can also cause some of the less severe complaints that people with an underactive thyroid have such as dry or flaky skin and constantly cold hands or feet.

Increased Susceptibiliy to Infection

While it's more associated with weight problems, the thyroid gland plays a large role in the body's immune system. When the body produces less hormone than is needed, one can become more susceptible to both viral and bacterial infections. Also things like sinus problems and sore throats become more common and often reoccurring.


Depression can not only be caused by an underactive thyroid, but has similar symptoms. Fatigue, loss of or increase in appetite and unexplained crying are all symptoms of both depression and hypothyroidism. To determine the difference between the two, a doctor should be consulted to run the proper blood tests.

Increased Weight

Since the thyroid gland is in charge of producing the hormones that control the metabolism, when it's not producing enough this can greatly affect one's weight. Some people may see a weight gain, while other people may just have severe problems losing weight.

Decreased Heart Rate

The heart rate is the number of beats the heart makes per minute. In someone who has hypothyroidism, the heart rate will be below normal. While heart rate can vary by person due to fitness level and activity, the average resting person has a heart rate of about 70 beats per minute.