Hypothyroidism: What Experts Suggest for Treating Low Thyroid Hormone Levels

Hypothyroidism: What Experts Suggest for Treating Low Thyroid Hormone Levels

Medicine is always changing. Updates in diagnosing problems come with better ways to diagnose and, in turn, treat medical conditions. Sometimes the updates show a better understanding of a condition, information that comes out of research and clinical studies. This past year, experts from the American Association of Clinical Endocrinologists (AACE) and the American Thyroid Association (ATA) came together to review and update issues specific to low thyroid hormone levels, also known as hypothyroidism [hahy-po-thahyroi-diz-uhm]. Here are some of the highlights from their review* and the suggestions that were made to those that treat this condition. *(To view the complete report, visit: https://www.aace.com/files/hypothyroidism_guidelines.pdf).

First, some background: The thyroid is a small gland weighing less than an ounce and is located at the front of your neck. It controls the pace at which every cell, tissue and organ in your body functions. Hypothyroidism occurs when the thyroid gland does not make enough thyroid hormone to meet your body’s needs. The more severe the hypothyroidism is, the more likely there will be symptoms such as fatigue, depression, weight gain, constipation and dry skin. This is a common condition. Over 10 million Americans have hypothyroidism. And many do not know they have it. Women are more likely to have it than men, and the chances for developing it go up as we get older. For example, over 10 percent of Caucasian women over 60 years of age in the United States and Canada are hypothyroid.

The thyroid makes two kinds of thyroid hormone: thyroxine, called T4, and T3. The thyroid’s output consists primarily of T4 (see Figure 1 below). Most of the T3 the body needs is made outside the thyroid, in organs and tissues that use T3, such as the liver, kidneys and brain.

The thyroid is under the control of the pituitary gland, located at the base of your brain, sometimes known as the “master” gland, because it controls functions of the thyroid and other glands in the endocrine system (see Figure 1 below). The pituitary gland sends a message in the form of thyroid-stimulating hormone (TSH) to your thyroid gland, telling it how much hormone to make. TSH levels in your bloodstream rise or fall depending on whether there is enough thyroid hormone in your system to meet your body’s needs. Higher levels of TSH push the thyroid to produce more hormone. Low TSH levels mean the thyroid is producing more than enough hormone. TSH levels can change a great deal with minor increases and decreases in T4. This is a very tightly regulated feedback process between the pituitary and the thyroid gland.

Why Does This Finely Tuned System Fail?

Worldwide--but not in the USA and other countries where there is enough iodine in food--too little iodine in the diet is the most common cause of hypothyroidism. In the USA and other countries where there is sufficient iodine in the diet, common causes of hypothyroidism are:

  • Chronic inflammation of the thyroid, known as Hashimoto’s thyroiditis, is the most common.
  • Surgical removal of the thyroid for:
    • Thyroid lumps or nodules, most of which are benign
    • An enlarged thyroid, also known as goiter, that is causing discomfort
    • An overactive thyroid
    • Radiation therapy, usually to treat an overactive thyroid

In contrast to a normal thyroid (Figure 1), hypothyroidism occurs when too little thyroid hormone (T4 and T3) is generated by the thyroid gland (Figure 2). In response, changes in the hypothalamus and the pituitary gland lead to increased TSH production in an effort to increase the thyroid’s output. But the diseased gland continues to lag in production of thyroid hormone, causing the body’s metabolism to slow down. Some portions of the damaged thyroid gland might become enlarged, leading to a goiter.

Illustrations reprinted from The Harvard Medical School Guide to Overcoming Thyroid Problems by Jeffrey R. Garber with Sandra Sardella White.

Less common causes of hypothyroidism are drugs, such as lithium [lith-ee-uhm], used to treat specific psychiatric conditions; amiodarone [am-ee-oh-darohn] for heart conditions; diseases of the pituitary gland affecting the production of thyroid stimulating hormone (TSH); and radiation to the thyroid for reasons other than an overactive thyroid.

What Do We Know About Hashimoto’s Thyroiditis?

It is five to 10 times more common in women than in men, occurs more frequently as we get older and is more common in people with other autoimmune diseases—such as Type 1 diabetes, celiac disease (sensitivity to gluten which is present in wheat, barley, and rye and – therefore – many foods containing them), lupus (affects many organs such as skin, joints and kidneys), rheumatoid arthritis, or pernicious anemia—and their families. Goiter (thyroid enlargement) may or may not be present. One of the keys to diagnosis is finding thyroid antibodies in the blood. The normal function of antibodies is to protect us from infection. With Hashimoto’s thyroiditis the immune system mistakenly produces antibodies against the thyroid and attacks it as if it did not belong there. Antibodies against the thyroid are anti-thyroglobulin antibodies (TgAb) and anti-microsomal/thyroid peroxidase antibodies (TPOAb). TPOAb tests predict going from mild to more advanced hypothyroidism, so it is recommended they be checked to help with the decision to treat mild hypothyroidism as well as in those with recurrent miscarriages. This is because miscarriages are more common in women with TPOAb, perhaps because they become hypothyroid during pregnancy.

Signs and Symptoms of Hypothyroidism

The symptoms of hypothyroidism may be mild and mistaken for other conditions, and, therefore, often are easily overlooked. Dry skin, cold sensitivity, fatigue, muscle cramps, voice changes and constipation are among the most common. Less common and usually just seen with severe hypothyroidism are hand numbness and pain from carpal tunnel syndrome due to nerves being compressed in the wrist, and sleep apnea, a form of interrupted, ineffective sleep seen in some who snore. With successful treatment, heart rates may rise from slow to normal. Cholesterol may go from high to normal and menstrual abnormalities, including irregular periods, can go away. But a diagnosis of ypothyroidism should not be made on the basis of symptoms alone!

Diagnosing Hypothyroidism

TSH levels are typically used in making a diagnosis in those with a normally functioning pituitary. Although TSH may not be the same for different ages and ethnic backgrounds, the majority of individuals without evidence of thyroid disease have a TSH below 2.5 mIU/L. So it has been suggested that the upper limit of the TSH reference range be lowered to 2.5 mIU/L. However, many patients with TSH concentrations in this range do not develop hypothyroidism, particularly if they do not have thyroid antibodies. Blood test confirmation of the diagnosis before treatment is absolutely necessary. T3 levels alone should not be used to diagnose hypothyroidism.

Screening for Hypothyroidism – Yes or No?

Universal screening is not recommended for patients who are pregnant or planning pregnancy, and there is no general agreement about screening entire populations for hypothyroidism. Testing in the following situations is recommended:

  • Autoimmune disease, such as Type 1 diabetes, lupus or rheumatoid arthritis
  • A first-degree relative with autoimmune thyroid disease such as Hashimoto’s thyroiditis
  • History of neck radiation to the thyroid gland including radioactive iodine therapy for hyperthyroidism and external beam radiotherapy for head and neck cancers
  • A prior history of thyroid surgery or dysfunction
  • An abnormal thyroid examination
  • Psychiatric disorders
  • Those over age 60, particularly Caucasian women
  • Patients taking amiodarone or lithium
  • Patients with features—either complaints or physical features - of hypothyroidism

Dr. Jeffrey Garber is an Associate Professor of Medicine at Harvard Medical School, chief of the endocrine division of Harvard Vanguard Medical Associates, and President of the American College of Endocrinology (ACE). His book, The Harvard Medical School Guide to Overcoming Thyroid Problems, and monograph Thyroid Disease: Understanding hypothyroidism and hyperthyroidism, Copyright ©2012, Harvard University, were written for members of the lay public interested in learning about thyroid disorders.