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Diagnosing Hypothyroidism

NYU Langone endocrinologists treat people with disorders of the endocrine system, including hypothyroidism. This hormonal disorder occurs when the butterfly-shaped thyroid gland, located in the neck, doesn’t produce enough of the hormone thyroxine, commonly known as T4.

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The thyroid helps regulate many of the body’s functions, including metabolism, heart rate, and body temperature. When a person’s thyroid doesn’t produce enough of this hormone, some body functions begin to slow.

Symptoms of Hypothyroidism

People with hypothyroidism, for instance, may have trouble losing weight, even if they are eating well and exercising. They may feel tired all the time or have difficulty concentrating. They may feel constipated. Some people notice that their hair and skin are drier than usual and may experience hair loss.

Many people with hypothyroidism are never properly diagnosed. If you are feeling run down, having trouble losing weight with proper diet and exercise, or having trouble concentrating, tell your doctor. He or she can determine whether your symptoms are caused by thyroid deficiency.

Causes of Hypothyroidism

Hypothyroidism can affect anyone at any age. It tends to occur more often in women than in men. Those with a family history of autoimmune thyroid disease, such as Hashimoto’s thyroiditis or Graves’ disease, or other autoimmune disorders have an increased risk.

There are several causes of hypothyroidism.


Hypothyroidism can occur after a person develops thyroiditis, which is an inflammation of the thyroid gland. There are several types of thyroiditis.

Thyroiditis initially triggers the release of stored thyroxine. This temporarily elevates the level of this hormone in the blood, causing thyrotoxicosis, often followed by a subsequent drop in the hormone level, leading to hypothyroidism. Mild thyroiditis can sometimes be observed without treatment, but more severe thyroiditis requires treatment during both its hyper- and hypothyroid phases.

Beta blockers are used to control symptoms of hyperthyroidism because they slow and protect the heart from the excess stimulation caused by increased levels of thyroid hormone. Thyroid replacement with thyroxine is necessary when the hypothyroid phase of thyroiditis is severe. Though the hypothyroid phase of thyroiditis is often transient, it can sometimes be permanent and lead to a lifelong need for thyroxine replacement.

Some people develop thyroiditis after an upper respiratory infection, but usually the trigger is unknown. In a small percentage of women, thyroiditis can occur within a year of giving birth, in a condition called postpartum thyroiditis.

The most common cause of hypothyroidism is Hashimoto’s thyroiditis, an autoimmune condition that’s also called chronic lymphocytic thyroiditis. A healthy immune system produces antibodies to recognize and destroy foreign substances, such as bacteria and viruses. But in people who have an autoimmune disorder, the immune antibodies mistakenly attack healthy tissues.

Long-term destruction of the thyroid gland by autoimmunity in Hashimoto’s thyroiditis can lead to decreased or even complete loss of thyroid function. People with the disease often have family members with autoimmune or thyroid conditions, although it is not completely understood why people develop it.

Hypothyroidism may also result from disease or injury to the cells in the pituitary, a gland in the brain that produces thyroid-stimulating hormone, or TSH, which prompts the thyroid to produce thyroxine. Since the problem is with the pituitary and not the thyroid, this condition is sometimes called central or “secondary” hypothyroidism. It’s rare and occurs most often after a head injury or brain surgery.


Other causes of hypothyroidism include thyroidectomy, in which the thyroid is partially or fully removed surgically, or destruction of the thyroid gland by the use of radioactive iodine to treat thyroid cancer or hyperthyroidism. This results in inadequate thyroxine production.


The use of certain medications can also cause hypothyroidism. These include lithium, which is used to manage mood disorders. Synthetic interleukins and other drugs used during chemotherapy can cause hypothyroidism, as can interferon alpha, which is used in the treatment of hepatitis.

Amiodarone, a medication used in managing heart arrhythmias, can cause both hypothyroidism and hyperthyroidism.

Diagnostic Tests

To diagnose hypothyroidism, your doctor asks about your symptoms and your medical history. He or she also performs a physical exam to determine whether your thyroid is enlarged or feels tender or inflamed. The doctor orders a blood test to confirm a diagnosis of hypothyroidism.

Blood Testing

The doctor takes a small sample of blood, which is analyzed in a laboratory to look for several markers, or indicators, of thyroid disease. The most sensitive of these is TSH. An elevated TSH level indicates that your thyroid has decreased function.

If the TSH level is borderline elevated after an initial blood test, your doctor may wait a few weeks and then repeat the test. Your doctor may also test your blood for thyroid antibodies, which may indicate that you have Hashimoto’s thyroiditis. Antibodies are present in almost all people with this condition.

If you are diagnosed with hypothyroidism, your doctor works with you to create a treatment program.

Our Research and Education in Hypothyroidism

Learn more about our research and professional education opportunities.