Diseases of the Thyroid

Posted By Donna Alvarado, Medical Editor

Presented by Kaniksha Desai, MD
Clinical Assistant Professor of Endocrinology

January 16, 2020

The thyroid gland may be small, but it is mighty. It regulates metabolism in your body, which drives almost every action your body takes to live.

Diseases of the thyroid, which grow common as people age, can affect everything from your lungs to your gut to your heart.

“It acts on almost every other organ in the body,” said Kaniksha Desai, MD, clinical assistant professor of endocrinology, in a presentation at the Stanford Health Library.

More than 10 percent of the population will have a thyroid problem at some time in their lives, Dr. Desai said. Women are about 5 times more likely to get a thyroid problem than men. The most common disorders are an underactive thyroid, an overactive thyroid, a thyroid nodule, or thyroid cancer.

The thyroid gland is located in your neck, at the bottom near your collarbones. To the left of your thyroid is your food pipe (the esophagus). Your vocal cords are also located next to your thyroid.

Big impact

Because it regulates metabolism, when the thyroid revs up—or slows down—that can have a big impact on your health. The thyroid gets its driving directions from another small gland: the pituitary.

Depending on what your body needs, the pituitary sends chemical messages to the thyroid to either increase or decrease the production of thyroid hormone. That chemical messenger is called thyroid-stimulating hormone, or TSH.

Signals sent

If the pituitary sends a TSH signal to the thyroid to speed up, the thyroid releases hormones called T3 and T4 to do that.

The T3 and T4 hormones head to their targets, such as the heart.

Imaging

Most of the time, doctors use 2 main kinds of tests to get pictures of the thyroid: ultrasound scans and radioactive iodine scans. Sometimes doctors need an additional scan, called CT or MRI to see the thyroid gland better.

A radioactive iodine scan shows what hormones the thyroid is making. Both radioactive iodine scans and ultrasound scans can show if parts of the thyroid are inflamed or overactive.

Four main disorders

There are 4 main kinds of thyroid diseases: underactive thyroid, overactive thyroid, thyroid nodules, and thyroid cancer.

♦Underactive thyroid (hypothyroidism)

Causes include:

  • Autoimmune disorder: In this condition, your body mistakes your thyroid cells for foreign material (like viruses or bacteria) and attacks them. That prevents the thyroid cells from making the hormones your body needs.
  • Iodine deficiencies: Without enough iodine, the thyroid can’t make hormones. This cause is uncommon in the U.S.
  • Surgery that removes part of your thyroid gland can make it underactive.
  • Thyroiditis: Inflammation of your thyroid can trigger an underactive or overactive thyroid.
  • Some medicines, including a heart medicine called amiodarone (given for irregular heartbeats), can cause an underactive thyroid.

Symptoms:

Symptoms of an underactive thyroid are pretty broad, because thyroid hormones act on almost every part of your body. The most common symptoms are:

  • Swelling in your neck, called goiter. Your thyroid is trying to compensate for being underactive, so it gets enlarged.
  • Weight gain
  • Feeling tired
  • Constipation
  • Cold intolerance
  • Infertility problems, with heavy menstrual cycles

Many of these symptoms can be caused by problems other than a thyroid disorder, so doctors make a careful diagnosis. That can include lab tests for TSH and thyroid hormones.

Treatment for an underactive thyroid is often a drug that is synthetic thyroid hormone. One mainstay, called levothyroxine, is a T4 hormone (brand names are Synthroid, Levoxyl, and Tirosint).

♦Overactive thyroid (hyperthyroidism)

Causes include:

  • An autoimmune disease called Grave’s disease
  • Thyroid nodules (spots on the thyroid gland)- can produce their own thyroid hormone
  • Thyroiditis: inflammation
  • Certain drugs

Symptoms of an overactive thyroid are also broad. They include:

  • Swelling in your neck (goiter)
  • Weight loss
  • Diarrhea
  • Tremors, shaking, and feeling overly energetic
  • Bulging eyes, caused by extra thyroid hormone deposited in eye muscles that causes them to swell.

An overactive thyroid is often diagnosed with help from lab tests for TSH and the 2 thyroid hormones (T3 and T4).

Treatment for an overactive thyroid includes 3 main options:

  • Anti-thyroid drugs, including methimazole and propylthiouracil (PTU). These drugs block the thyroid from making extra thyroid hormone.
    These drugs can have side effects, so some people can’t take them for a long time.
  • Radioactive iodine
    Given by pill, this drug burns off thyroid cells so that they stop producing thyroid hormone.  Once your thyroid stop producing then you will need to take thyroid hormone replacement for the rest of your life.
  • Surgery
    Surgery removes the entire thyroid gland so that it doesn’t produce thyroid hormone. Again, that requires you to take thyroid hormone replacement therapy for the rest of your life.

♦Thyroid nodules

Thyroid nodules are growths on the thyroid gland. More than 50 percent of people over age 50 have a thyroid nodule.

Often, thyroid nodules don’t cause any symptoms. If they are big, however, they can bulge out from your neck and press on nearby parts of your neck.

Symptoms of large nodules include:

  • Trouble breathing
  • Trouble swallowing

An ultrasound scan can identify a thyroid nodule.

Lab tests can reveal if a large nodule is causing the thyroid gland to produce too much thyroid hormone. Sometimes a biopsy is done.

“The good news is that most of these thyroid nodules are not cancer,” Dr. Desai said. About 5 to 10 percent are cancer.

Sometimes the biopsy comes back as an indeterminate result – in which the cells are not normal, but they are not cancer either.

For this gray area, an additional test is done to reveal molecular markers on the cells, which can rule out cancer and avoid surgery.

“If it comes back as cancer, we have to remove it,” Dr. Desai said.

Noncancerous thyroid nodules may not need any treatment if they are not causing troublesome symptoms. Most of these nodules don’t grow much over the years, Dr. Desai said.

Treatment for large nodules or those causing problems includes:

  • Surgery, the traditional treatment
  • A newer procedure, soon to be available at Stanford, it is called radiofrequency ablation. “We use heat on the end of the needle that’s doing the biopsy, and you’re burning the nodule,” Dr. Desai said.

♦Thyroid cancer

Thyroid cancer occurs in about 4 percent of women, making it the 6th most common cancer. For most, it is treatable.

“The number of deaths from thyroid cancer is pretty small,” Dr. Desai said.

Thyroid cancer often appears like a nodule at first. “Unfortunately, most patients with thyroid cancer actually don’t have symptoms,” Dr. Desai said.

Symptoms, if they do occur, are similar to those of noncancer nodules, including:

  • Trouble swallowing or breathing
  • Neck swelling
  • Hoarseness in your voice, caused by pressure on your vocal chords.

Thyroid cancer is diagnosed using the same tests used to check thyroid nodules, including:

  • An ultrasound scan, done for the neck (which includes both the thyroid gland itself and the lymph nodes in the neck around the thyroid gland)
  • A fine needle biopsy to confirm thyroid cancer

Doctors usually determine the stage of the thyroid cancer. Stage 1- Stage 4, with Stage 1 as having the best prognosis with a 5-year survival rate greater than 99%.

Treatment for thyroid cancer includes these main options:

  • Surgery to remove the cancer which cures a lot of the cancer cases
  • Radioactive iodine treatment if the thyroid cancer has spread to lymph nodes and other areas of the body
  • Suppressive hormone therapy to keep the hormone TSH low to prevent growth of the cancer
  • Chemotherapy for advanced thyroid cancer which cannot be treated with surgery and/or radioactive iodine

After treatment, long-term follow-up care usually involves:

  • Ultrasound scans to make sure the cancer is gone and doesn’t return
  • Checking for a biochemical “tumor marker,” called thyroglobulin which is produced by thyroid cancer cells
  • Testing to make sure your TSH is in the recommended range for your cancer status

For more information:
American Thyroid Association
American Association of Clinical Endocrinologists
ThyCa: Thyroid Cancer Survivors’ Group

Kaniksha Desai, MD

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