The most common type of thyroid disorder, hypothyroidism occurs when the thyroid gland fails to produce enough thyroid hormone—hormones which influence essentially every organ, every tissue and every cell in the body. Hypothyroidism affects an estimated 15 million Americans, particularly women and the elderly.

In the U.S., the most common type of hypothyroidism is Hashimoto’s Disease, a condition caused when the immune system produces killer lymphocytes that destroy the thyroid. As the damaged thyroid gland produces less thyroid hormones, the pituitary gland secretes more thyroid-stimulating hormone (TSH) to encourage the thyroid to work harder. This increased demand on the thyroid may cause it to enlarge, resulting in what is commonly known as a goiter. Antibodies are produced that serve as a diagnostic test for Autoimmune Disease.

Signs and Symptoms

Fatigue, irregular menstrual periods, impotence, high cholesterol, hoarse voice, mood swings, difficulty swallowing, forgetfulness, intolerance to cold, and dry, coarse skin and hair.

Detection and Diagnosis

Hypothyroidism may be difficult to detect. Its signs and symptoms are easily confused with other conditions, such as the natural aging process, menopause or stress. Many patients remain undiagnosed and untreated for years due to their lack of awareness of hypothyroidism and its signs and symptoms.

Fortunately, even mild hypothyroidism can be detected by a sensitive TSH (thyroid stimulating hormone) test, which enables physicians to identify thyroid disorders much earlier than with previous tests.


The goal for treating hypothyroidism is to restore normal blood levels of thyroid hormone by replacing missing hormones. The treatment of choice for hypothyroidism involves supplementing the body’s naturally produced hormone with a synthetic hormone tablet, levothyroxine sodium, which is generally taken for life. After the patient starts taking this hormone tablet, the treatment must include periodic TSH tests to monitor thyroid hormone levels.

Because patient dosage requirements may change over time according to age, body weight, cardiovascular status and other diseases or medications, it is essential to monitor patients’ medication needs on a regular basis. Monitoring precise dosages effectively prevents recurrence of symptoms of hypothyroidism and prevents over-replacement, which can in turn lead to hyperthyroidism.

Hypothyroid patients should not switch to different brands of levothyroxine sodium without consulting a physician. Both the American Association of Clinical Endocrinologists (AACE) and the American Thyroid Association (ATA) have released clinical guidelines recommending that patients be retested and their dosages adjusted accordingly if they switch levothyroxine sodium products. AACE further advocates that physicians treat patients with the same brand of levothyroxine throughout their lifetime. Be aware of pseudo-diagnoses such as Wilson’s Disease (see under “Myths and Facts”).