Definition

The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces hormones that control metabolism. Hypothyroidism results when the thyroid gland doesn’t produce enough thyroid hormone. The most common form of hypothyroidism is Hashimoto’s thyroiditis.

Causes

Hashimoto’s thyroiditis is an autoimmune disorder. The immune system produces antibodies that attack cells of the thyroid gland.

Hypothyroidism may also be caused by:

• Congenital defects of the gland or how it works
• Iatrogenic—occurs as the result of surgery or radiation therapy for thyroid cancer treatment
• Iodine deficiency—rare in the US
• Pituitary deficiency
• Unknown reasons

Risk Factors

Hypothyroidism is more common in women, and in those aged 65 years and older. Other factors that may increase your risk of hypothyroidism include:

• Family history of hypothyroidism
• Autoimmune diseases, such as systemic lupus erythematosus, celiac disease, type 1 diabetes, or rheumatoid arthritis
• Certain health conditions, such as infiltrative disorders, cancer, or infections
• Surgery, radiation therapy, or radioablation in the neck region
• Certain medications, such as lithium, iodine, or interleukins
• Pituitary adenoma —benign tumor of the pituitary gland

Symptoms

You may not have symptoms of hypthyroidism. In those that have symptoms, hypothyroidism may cause:

• Fatigue
• Weakness
• Coarse, brittle hair, and hair loss
• Facial puffiness
• Dry skin
• Swollen hands or feet
• Cold intolerance
• Weight gain
• Constipation
• Achy feeling all over
• Depression and irritability
• Memory loss
• Difficulty concentrating
• Blurred vision
• Menstrual abnormalities or infertility

Symptoms of severe or long-term hypothyroidism causes:

• Slow heart rate
• Depressed breathing
• Hypothermia —low body temperature
• Coma

Diagnosis

You will be asked about your symptoms and medical history. A physical exam will be done.

Tests may include blood tests to check levels of thyroid stimulating hormone (TSH), and/or free T4. Other tests may be recommended to rule out health conditions that are similar to hypothyroidism.

Treatment

Thyroid replacement therapy involves taking medications that replace the function of the thyroid gland. This therapy may also prevent cancer cell growth in people who had surgery or radiation treatment for thyroid cancer.

People with Hashimoto’s thyroiditis are monitored as long as they have normal thyroid function and remain symptom-free. Once function decreases or symptoms appear, treatment is started with thyroid replacement therapy.

Prevention

There are no current guidelines to prevent hypothyroidism.

The American Academy of Pediatrics and United States Preventive Services Task Force recommend screening all newborns for congenital hypothyroidism. If you are at high risk for developing hypothyroidism talk to your doctor about annual screening.

WomensHealth.gov—US Department of Health and Human Services http://womenshealth.gov

Thyroid Foundation of Canada http://www.thyroid.ca

Escobar-Morreale HF, Botella-Carretero JI, Escobar del Rey F, et al. Treatment of hypothyroidism with combinations of levothyroxine plus liothyronine. J Clin Endocrinol Metab. 2005;90:4946-4954.

Hypothyroidism in adults. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed
Updated December 12, 2014. Accessed December 16, 2014.

Roberts CG, Ladenson PW. Hypothyroidism. Lancet. 2004;363:793-803.

Surks MI, Ortiz E, Daniels GH, et al. Subclinical thyroid disease: scientific review and guidelines for diagnosis and management JAMA. 2004;291:228-238.

Thyroid hormone treatment. American Thyroid Association website. Available at:
http://www.thyroid.org/thyroid-hormone-treatment
Published June 4, 2012. Accessed November 25, 2013.