Hypothyroidism is a medical condition that occurs if your thyroid--a small gland within your neck that is part of your endocrine system--produces abnormally low levels of thyroid hormones 1. These thyroid hormones are responsible for regulating your metabolism, or how your body uses energy. About 5 percent of people in the United States have this condition and the majority of them are women, based on estimates from the National Endocrine and Metabolic Diseases Information Service 3. An insufficient supply of thyroid hormones within your body can cause a number of side effects, all of which should be discussed with your doctor.

Weight Gain

Weight gain is one of the primary side effects associated with hypothyroidism. Low levels of thyroid hormones within the body slow the metabolism of ingested food sources. This causes a decrease in the rate at which your body burns calories, which causes weight gain. This condition can also cause fluid retention, which can lead to swelling of facial tissue or body muscles. If you have hypothyroidism, you can develop an increase in body weight even if your diet remains unaltered.


Low levels of thyroid hormones can contribute to extreme tiredness or fatigue. A slower metabolism also decreases how quickly your cells obtain energy from ingested food, which can lead to chronic fatigue.


Hypothyroidism can cause changes in bowel movements. Low thyroid hormone levels can make it difficult or impossible for you to produce a stool--a condition known as constipation. Constipation can cause additional symptoms, such as abdominal cramping, pain or bloating, and may contribute to weight gain. If this condition does not resolve, speak with a doctor for further care.

Hair Loss

Decreased thyroid hormone levels can cause changes in the appearance of your hair. Certain people can develop coarse, dry or dull hair due to this condition. Hair loss, which can occur from the scalp or eyebrows, is also a common side effect of hypothyroidism.

Decreased Heart Rate

Hypothyroidism causes some people to develop a slowed heart rate, the New York Thyroid Center at Columbia University Medical Center warns 1. Such symptoms should be discussed with your doctor as soon as possible.

Dry or Discolored Skin

An underactive thyroid gland can also cause dry or discolored skin. Dry skin can appear red or flaky and may become itchy or irritated. Skin discoloration due to hypothyroidism can cause your skin to appear yellow or orange--especially on the palms of your hands or the soles of your feet.

Vocal Alterations

Abnormally low levels of thyroid hormone can cause enlargement of your thyroid gland--a condition called goiter--which can lead to problems with your voice box. If you have hypothyroidism, your voice may sound dry, raspy or hoarse, making it difficult for you to speak normally.

Cognitive Impairment

Hypothyroidism can cause cognitive difficulties in some people. You may be unable to concentrate during your normal activities, or you may become forgetful or have difficulty making decisions.


Hypothyroidism can also lead to mood alterations, such as depression or anxiety. A study published in the March 1993 issue of "The American Journal of Psychiatry" reported that 56 percent of subclinical hypothyroidism patients reported experiencing depression at some point during their lives. In contrast, the lifetime frequency of depression was only 20 percent in healthy patients.

Menstrual Cycle Changes

Women with hypothyroidism can develop irregular or abnormally heavy menstrual periods. Some women can also experience miscarriages or may be unable to become pregnant (infertility) because of this condition.