Signs and Symptoms of an Underactive Thyroid With Blood Test Results

Updated April 17, 2017

The thyroid is a butterfly-shaped gland that is located in the front of the neck. It produces hormones that control how the body uses energy. Instances of an underactive thyroid, in which the gland is not producing enough thyroid hormone, are known as hypothyroidism and can be confirmed through a blood test. Hypothyroidism has a variety of signs and symptoms.

Tiredness and Weakness

If a person feels unusually tired or weak, this may be a symptom of an underactive thyroid. An associated symptom is depression. With the slowing down of the thyroid gland and the decreased production of thyroid hormone, all body systems are affected. Without the proper levels of thyroid hormone, the muscles won't function as efficiently as they should, resulting in tiredness and weakness. The lack of thyroid hormone also negatively affects the chemical balance in the brain, which can result in depression.

Brittle Nails

Fingernails and toenails peeling, splitting, and/or breaking easily may be a sign of hypothyroidism. Fingernails and toenails are made up of layers of protein. The reduced production of thyroid hormone caused by an underactive thyroid can result in a lack of production of the proteins needed to maintain nail strength and integrity. Although brittle nails can be due to extreme dryness of the nail, they may also be a symptom of hypothyroidism, and so a physician should be consulted if they persist.

Dry Skin

Dry skin occurs when the skin's natural moisture is decreased. Hypothyroidism can result in dry skin, manifested as chapping, redness, scaling, itching, cracking, fissures, and tenderness, which is a result of the underactive thyroid being unable to properly maintain the skin's moisture levels.


Constipation occurs when an individual's bowel movements are less frequent, harder, or become more painful. A reduction in the production of thyroid hormone causes the digestive system to not process food effectively, causing the difficulty and pain in passing a stool that is associated with constipation. Although diet can be the reason behind constipation, hypothyroidism is another more serious cause.

Memory Problems

Memory problems or the inability to think clearly may be another sign of hypothyroidism. An underactive thyroid may cause an individual to be more forgetful or to have more muddled thoughts. As mentioned earlier, a decreased production of thyroid hormone affects the neurological system, including the brain. Processes involved in cognitive thinking and memory rely on thyroid hormone to function effectively.

Abnormal Menstrual Periods

In women, one sign of hypothyroidism may be irregular or abnormally heavy menstrual periods. The reproductive system and the hormones controlling the menstrual cycle are regulated by thyroid hormone. When the thyroid is underactive, the hormones oestrogen and progesterone, which control the menstrual cycle, do not signal menstruation regularly. This results in irregular periods and/or abnormally heavy periods.

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About the Author

Kimberly Wylie has been a professional, full-time freelance writer for nearly a decade. She is the author of the book "Hiring the Right Candidate" and has written for several online and print publications. A gifted wordsmith, her work has included everything from movie scripts to patent documentation.