Thyroid Gland: Too Slow or Too Fast?

By Dianne S. Cheung, MD, MPH

Hypothyroidism [hye-po-THIGH-roi-diz-uhm] (underactive thyroid gland)

“Doctor, I’m gaining weight. Is it my thyroid’s fault?”

This is perhaps the most common question to endocrinologists [en-doh-krih-NOL-uh-jists] in the office. Sometimes the answer isn’t what most patients would like to hear.

Hypothyroidism is a condition when the body does not produce enough thyroid hormone. The thyroid, a butterfly-shaped gland located in the middle of the neck, is responsible for regulating the body’s metabolism. When this gland doesn’t make enough thyroid hormone (T3 and T4), the ability for the body to use and store energy slows down. In turn, production of T3 and T4 is regulated by a gland in the brain called the pituitary [pi-TOO-i-ter-ee] gland, which produces thyroid-stimulating hormone (TSH). TSH stimulates the thyroid gland to produce T3 and T4. In hypothyroidism, TSH is higher than normal, and T3 and T4 are low.

There are 2 common causes of hypothyroidism. Autoimmune hypothyroidism, also called Hashimoto’s thyroiditis, is caused by the body destroying the thyroid gland (an “autoimmune” process). Over 90% of patients with chronic autoimmune thyroiditis have anti-thyroid antibodies. The condition can easily be treated with thyroid hormone replacement. Thyroid disorders can also occur with the use of certain medications. Hypothyroidism is more common in women, and many but not all patients have a goiter (an enlarged thyroid gland causing a swollen neck).

Diagnosis of hypothyroidism is mainly made with blood tests, since the symptoms of low thyroid production are not specific to the condition. These symptoms include

  • Weight gain
  • Fatigue
  • Forgetfulness
  • Constipation
  • Dry skin
  • Hair loss
  • Cold intolerance
  • Irregular menses

Having these symptoms does not necessarily mean you have hypothyroidism. Testing the blood for TSH is part of the medical evaluation for thyroid problems. Elevated TSH levels establishes a diagnosis of hypothyroidism. The more severe, the higher the TSH level and lower the T4 levels will be.

Seeing your primary care doctor or an endocrinologist is the first step if you suspect hypothyroidism. A simple blood test for TSH can be done, and if it is high, it can be confirmed with a repeat TSH with a free T4 level. Hashimoto’s thyroiditis tends to run in families, so if Grandma had a goiter and took thyroid medication, and you have weight gain and fatigue, definitely get a blood test to check your thyroid.

As the thyroid loses its function, patients may develop a goiter (enlarged thyroid gland). Other than looking odd, it can cause symptoms in the neck such as hoarseness, choking, and persistent coughing.

Treatment of hypothyroidism involves replacing thyroid hormone. The most common thyroid replacement used is levothyroxine [lee-voh-thigh-ROX-een], a synthetic T4 replacement. T4 stays in the body for many days and is converted to active T3 as needed.

Levothyroxine should be taken on an empty stomach in the morning, an hour before breakfast, and it is best to wait at least four hours before taking medicines such as oral calcium or iron replacement, bile acid-binding resins, and proton pump inhibitors, as well as soy and fiber products.

Patients can find relief of many of their symptoms within a few weeks of initiating thyroid replacement, but it may take up to a few months to reach a normal thyroid state.

Hyperthyroidism [hye-per-THIGH-roi-diz-uhm] (overactive thyroid)

“Doctor, I can’t sleep and I’m anxious all the time.”

The flip side of hypothyroidism is hyperthyroidism.

Graves’ disease is the most common form of hyperthyroidism. This condition makes the immune system produce an antibody that makes the thyroid gland produce more thyroid hormone. As a consequence, the pituitary gland slows down or shuts off production of TSH, while T4 and T3 levels are higher than the normal range in the blood. The added thyroid hormone affects the body by “speeding up” many of the processes, causing some or all of the following symptoms:

  • Rapid or irregular heartbeats
  • Weight loss
  • Anxiety and nervousness
  • Tremor (shaking)
  • Insomnia
  • Diarrhea or frequent bowel movements
  • Heat intolerance
  • Fatigue
  • Irregular menses in some women
  • Erectile dysfunction (impotence) in some men

Graves’ disease is more common in women. A goiter often occurs along with excessive thyroid hormone production. Some patients develop an eye problem known as Graves’ orbitopathy [or-bit-AH-pah-thee], which causes dry irritated eyes, double vision (diplopia) and eyes that stick out due to swelling of the eye muscles.

Hyperthyroidism can also occur due to a toxic nodular goiter. Another cause can be a viral infection called subacute or granulomatous [gran-yuh-LOH-muh-tus] thyroiditis, in which the thyroid gland becomes inflamed and painful. Fortunately, when the viral infection resolves, so does the thyroiditis. There is also painless thyroiditis that can occur when the thyroid gland becomes inflamed temporarily, such as after giving birth.

The first step in diagnosis is to measure the amount of TSH, which should be low, and T3 and T4 levels should be high. Since there are several causes of hyperthyroidism in which the thyroid gland goes back to normal by itself (painless thyroiditis and subacute thyroiditis), it is important to determine the cause. This may require a radioiodine [ray-dee-oh-EYE-oh-dyne] uptake and scan.

Treatment for hyperthyroidism includes medication, radioactive iodine, and surgery. Anti-thyroid drugs such as methimazole [me-THIM-uh-zohl] and propylthiouracil [proh-pil-thigh-oh-YOOR-uh-sil] (PTU), decreases the amount of thyroid hormone made. Both drugs work well, but due to recent reports of liver failure in patients on PTU, methimazole is now preferred. Methimazole and PTU may cause rash, hives, and stomach upset. Rarely, a condition called agranulocytosis [uh-gran-yuh-loh-sahy-TOH-sis] (low white blood cells) can occur. Beta blockers, such as propranolol [pro-PRAN-oh-lawl], are also prescribed to control symptoms such as tremor (shaking), irregular heart beat, and anxiety. Medication may need to be taken for several months or up to a few years before the thyroid returns to normal. Hyperthyroidism can come back and require repeat treatment with medication, radioactive iodine, or surgery.

Some patients who do not respond to medications or who cannot handle the side effects of the medications may decide to receive radioactive iodine. Radioactive iodine is taken in capsule or liquid form and destroys part or a majority of the thyroid gland. Patients may need to go on thyroid replacement therapy after treatment.

A few patients will need surgery. Reasons for surgery include a large goiter that is causing pressure symptoms, unable to handle the side effects of antithyroid drugs, unable to receive radioactive iodine, or possibly have thyroid cancer (rare). There are patients with Graves’ orbitopathy whose eye disease worsens once they receive radioactive iodine treatment, so surgery could be an option if hyperthyroidism is not controlled on antithyroid drugs.

Whichever thyroid condition you may have, there is an effective treatment available. If you suspect that you may have either hypothyroidism or hyperthyroidism, please go see your primary care doctor or endocrinologist, because there is a remedy waiting for you.

Dr. Dianne S. Cheung is board-certified in Endocrinology, Diabetes and Metabolism having completed her fellowship training at the UCLA Ronald Reagan Medical Center. Dr. Cheung is currently in private practice with South Bay Endocrine Associates in Torrance, California. She is active member of the Inpatient Diabetes Committee at Torrance Memorial Medical Center. She has presented abstracts and posters on diabetes and thyroid cancer at national conferences, including The Endocrine Society and the American College of Physicians. Dr. Cheung has published in peer-reviewed medical journals, and her research interests are in diabetes and thyroid disease.