DEAR MAYO CLINIC: I recently was diagnosed with mild hypothyroidism that isn't causing symptoms. My doctor says I don't need treatment now, but she wants me to come back for regular checkups. Does hypothyroidism usually get worse over time? If it does, how is it treated?

ANSWER: For mild cases of hypothyroidism, not all patients need treatment. Occasionally, the condition may resolve without treatment. Follow-up appointments are important to monitor hypothyroidism over time, however. If hypothyroidism doesn't go away on its own within several months, then treatment is necessary. If left untreated, this condition eventually may lead to serious health problems.

The thyroid gland is a small butterfly-shaped gland in the front of the neck that makes the hormones triiodothyronine, or T3, and thyroxine, or T4. Those hormones affect all aspects of your metabolism. They maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate, and help regulate the production of proteins. The amount of thyroid hormones your body makes is regulated by another hormone called thyroid stimulating hormone, or TSH, that's produced by the pituitary gland.

Hypothyroidism develops when the thyroid doesn't make enough hormones. As a result, your metabolism slows down. As thyroid activity slows, the level of T4 in your body decreases, and the level of TSH increases to encourage the thyroid gland to raise T4 production.

Some mild cases of hypothyroidism, called subclinical hypothyroidism, are associated with an elevated TSH while the T4 level stays within the normal range. At that point, the condition may not produce any noticeable symptoms. But if the decrease in T3 and T4 continues (referred to as overt hypothyroidism), it can affect many bodily functions.

Common early symptoms of hypothyroidism include unexplained weight gain, fatigue and low energy. It also may cause dry skin, constipation, sensitivity to cold, a puffy face, muscle weakness, hoarseness, and joint pain or stiffness.

Hypothyroidism can affect the heart by slowing the heart rate. It also has an effect on the body's ability to effectively metabolize cholesterol. That can lead to a rise in blood cholesterol, increasing the risk of heart disease and cardiovascular events, such as heart attack and stroke.

Hypothyroidism can affect the brain and lead to difficulty with concentration and memory. It can affect the gastrointestinal system, too, causing less frequent bowel movements and constipation. In premenopausal women, hypothyroidism can affect the menstrual cycle and fertility.

Hypothyroidism is diagnosed using a blood test that measures the level of thyroid hormones in the body. That blood test is repeated at regular intervals to monitor thyroid hormone levels. If hypothyroidism persists for more than a few months, treatment often is recommended.

Standard treatment for hypothyroidism involves taking a daily oral medication called levothyroxine, a synthetic form of thyroid hormone. It restores the body's hormone levels to normal, which reverses the signs and symptoms of hypothyroidism.

The amount of levothyroxine needed varies from person to person. To determine the right dosage for you, your health care provider will regularly check your level of thyroid hormone. The first blood test is done six to eight weeks after you start taking the medication. After that, blood levels generally are checked every six months. Then, if the levels stay within the normal range for several years, monitoring usually can switch to once a year. Some medications, including nonprescription (over-the-counter) ones, can affect the absorption or metabolism of thyroid hormone tablets, so you should notify your health care provider whenever you begin or discontinue other medications.

It's important to receive the correct amount of this medication because too little levothyroxine won't adequately control hypothyroidism and too much can cause side effects, such as increased appetite, insomnia, shakiness, and heart palpitations or an irregular heartbeat.

Work with your health care provider to set up a schedule for your follow-up visits. With careful monitoring and treatment, when necessary, hypothyroidism can be effectively controlled, eliminating symptoms and decreasing your risk of complications from this condition. — Dr. Robert C. Smallridge, Endocrinology, Mayo Clinic, Jacksonville, Florida

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• Mayo Clinic Minute: How the thyroid affects the heart published 9/11/19
• Study finds similar cardiovascular outcomes for generic, brand-name drugs for hypothyroidism published 6/19/19
• Consumer Health: Understanding hypothyroidism published 1/26/18
• Women’s Wellness: Hypothyroidism and pregnancy published 2/1/17

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