Thyroid problems, when undiagnosed and untreated, can cause a variety of uncomfortable symptoms, including weight gain or inability to lose weight, depression, anxiety, fatigue and infertility.

Because symptoms can sometimes be broad, thyroid disease is often misdiagnosed as a mental-health issue, and symptoms can be seen as attributed to other factors such as lifestyle, lack of sleep, overeating or stress.

Thyroid problems are mostly genetic, and thyroid problems do run in the family. They are more common in young women but can happen at any age including in the elderly, depending on the specific type of thyroid problem. Iodine deficiency, exposure to goitrogens (foods or other substances that can cause goiter) and other environmental factors may also play a part.

The thyroid gland is a small, butterfly-shaped gland in the neck. when the thyroid is its normal size, you can’t feel it. This gland controls how quickly the body uses energy, makes proteins, and controls how sensitive the body is to other hormones. it does this by producing thyroid hormones called T4 and T3. These hormones act throughout the body to influence metabolism, growth and development as well as body temperature.

During infancy and childhood, adequate thyroid hormone is crucial for brain development. Thyroid health also is especially important especially for women of childbearing age, as this affects fetal development and pregnancy outcome.

When the thyroid works normally, it produces and secretes the amount of T4 and T3 hormones necessary to keep things moving at their proper pace.

The most common problems of the thyroid consist of an overactive thyroid gland, known as hyperthyroidism, and an underactive thyroid gland, known as hypothyroidism. Of the two, hypothyroidism is more common.

In the United States, the most common cause of hypothyroidism is an autoimmune disease called Hashimoto’s thyroiditis, in which your own body makes antibodies that attack the thyroid cells. it cannot be prevented but is easily treated with replacement thyroid hormone pills. Iodine deficiency as a cause for hypothyroidism is more common outside the United States; it can be prevented by adequate intake of iodine in the diet.

This is why the U.S. government puts iodine in salt and other food products.

Common symptoms of hyperthyroidism include anxiety, insomnia, rapid weight loss, diarrhea, high heart rate, high blood pressure, eye sensitivity or bulging, and vision disturbances. Common symptoms of hypothyroidism include feeling cold all the time, fatigue, weight gain, constipation, difficulty concentrating, fluid retention, depression, body pain and slow reflexes.

While there is no consensus from either the U.S. Preventive Service Task Force or the Endocrine Society on whether to check for thyroid issues during annual or regular physical exams, if a patient suspects thyroid dysfunction based on any of the symptoms discussed, it can be diagnosed by simple blood tests.

Zinnia T. San Juan, M.D., is an assistant professor and a specialist in endocrinology with the Division of Endocrinology, Department of Internal Medicine, Texas Tech University Health Sciences Center Paul L. Foster School of Medicine.