Everything You Ever Wanted to Know About the Thyroid (but were afraid to ask…) Caroline Messer, MD Board Certified Internist, Endocrinologist, and Physician Nutrition Specialist

Topics Thyroid Nodules Hyperthyroidism Hypothyroidism Frequently asked questions dispersed throughout talk

Introduction

The thyroid is a butterfly-shaped gland in the middle of the neck, located below the larynx (voice box) and above the clavicles (collarbones) FAQ: If I have an issue with my parathyroid, does this affect my thyroid hormone levels?

Thyroid function is controlled by a gland located just below the brain, known as the pituitary. The pituitary produces thyroid stimulating hormone (TSH), which stimulates the thyroid to produce T3 and T4. These hormones regulate how the body uses and stores energy.

very small changes in serum free T4 concentrations induce very large reciprocal changes in serum TSH concentrations. As a result, thyroid function is best assessed by measuring serum TSH, assuming the absence of pituitary or hypothalamic disease.

Thyroid Nodules

This figure shows a thyroid nodule on the left side of the thyroid This figure shows a thyroid nodule on the left side of the thyroid. Thyroid nodules are round or oval-shaped and differ from the surrounding normal thyroid tissue. A person may have one or more thyroid nodules.

Thyroid Nodules Thyroid nodules are very common; up to half of all people have at least one nodule, although most do not know about it Most nodules don’t change the amount of thyroid hormone in the body, but some cause the thyroid to make too much hormone. These nodules are very rarely cancerous. FAQ: Can thyroid nodules decrease the amount of thyroid hormone my body is making?

Causes of Nodules Thyroid nodules can be caused many different conditions. Reassuringly, about 95 percent of all thyroid nodules are caused by benign (non-cancerous) conditions.

Possible Symptoms Asymptomatic: found on routine exam or during imaging test performed for another condition Difficulty swallowing, voice hoarseness, shortness of breath Symptoms from having too much thyroid hormone

Diagnosis Normal TSH or high TSH: the next step is to have a thyroid ultrasound and fine needle aspiration biopsy (FNA) Additionally, if TSH is high, thyroid antibodies should be checked to look for Hashimoto’s thyroiditis

Diagnosis: Thyroid Ultrasound Thyroid ultrasound should be performed on all patients with a suspected nodule or nodular goiter on physical examination or with nodules incidentally noted on other imaging studies (carotid ultrasound, CT, MRI or PET scan) Thyroid ultrasonography is used to answer questions about the size and anatomy of the thyroid and nearby structures in the neck Findings can be used to select nodules that require FNA biopsy based on size and features

Diagnosis: FNA Thin needle used to remove small tissue samples from the nodule. Samples are examined with a microscope. FNA biopsy can be performed in the office with a local anesthetic (numbing medicine) Accurately identifies cancer in a suspicious thyroid nodule. In some cases, the biopsy does not contain enough tissue to make a diagnosis, and surgery is necessary Results of the biopsy will be one of the following: Benign (non cancerous) Malignant (cancer) Possible or suspicious for malignancy Non diagnostic or insufficient

Diagnosis: Thyroid Scan Low TSH: the nodule may be producing high levels of thyroid hormone The next step is to have a thyroid scan to see if the nodules are producing thyroid hormone

Thyroid Nodule Diagnosis: Thyroid Scan Can help determine if a nodule is producing thyroid hormone (i.e., “hot” or “toxic”) Performed after swallowing a small dose of a radioactive substance Nodules that absorb the substance are usually not cancerous Nodules that do not absorb the substance are called “cold,” and have a 5% risk of being cancerous Nuclear medicine diagnostic procedures have been used for more than five decades, and there are no known long-term adverse effects from such low- dose exposure. FAQ: Can a thyroid scan itself cause cancer because of the radioactive iodine?

Thyroid Scan Results

Treatment: Depends on Type of Nodule Watching & waiting – we don’t always treat nodules right away. We will often repeat yearly thyroid ultrasounds to monitor their size Radioactive iodine – comes in a pill or liquid that you swallow. Has a small amount of radiation and can destroy a lot of the thyroid gland. Used only to treat nodules that make too much thyroid hormone. Surgery to remove the thyroid nodule – a procedure to drain fluid from the thyroid nodule, if it is filled with fluid FAQ: I was placed on synthroid many years ago to shrink the size of my nodule(s). Does this work?

Hyperthyroidism

What is it? Hyperthyroidism is the medical term for an overactive thyroid (hyper = excessive) In people with hyperthyroidism, the thyroid gland produces too much thyroid hormone When this occurs, the body's metabolism is increased, which can cause a variety of symptoms

Symptoms Anxiety, irritability, trouble sleeping, even psychosis or depression Weakness (particularly the upper arms and thighs, making it difficult to lift heavy items or climb stairs) Tremors (of the hands) Perspiring more than normal, difficulty tolerating hot weather Rapid or irregular heartbeats

Symptoms Fatigue Weight loss in spite of a normal or increased appetite Frequent bowel movements Some women have irregular menstrual periods or stop having their periods altogether. This can be associated with infertility Men may develop enlarged or tender breasts, or erectile dysfunction, which resolves when hyperthyroidism is treated

Causes: Graves’ Most common cause of hyperthyroidism Not clear why it develops in most people, although it is more common in certain families In people with Graves' disease, the immune system produces an antibody that stimulates the thyroid to produce too much thyroid hormone Most common in women between the ages of 20-40, but can occur at any age in men or women

The thyroid gland enlarges (called a goiter) and makes excessive amounts of thyroid hormone, causing symptoms of hyperthyroidism Some people develop eye problems (called Graves' ophthalmopathy), which causes dry, irritated or red eyes, and double vision. Others develop swelling behind the eyes that causes the eyes to bulge out (figure 2), although this is less common. In its most severe form, people with Graves' ophthalmopathy can develop inflammation of the optic nerves, which can result in loss of vision.

Hyperthyroidism: Nodules One or more thyroid nodules (small growths or lumps in the thyroid gland) can produce too much thyroid hormone The nodule is then called a hot nodule, toxic nodule or toxic nodular goiter

Hyperthyroidism: Thyroiditis Painless ("silent” or “lymphocytic") thyroiditis and postpartum thyroiditis are disorders in which the thyroid becomes temporarily inflamed and releases thyroid hormone into the bloodstream, causing hyperthyroidism Postpartum thyroiditis can occur several months after delivery. Symptoms may last for several months, often followed by months of hypothyroid symptoms, such as fatigue, muscle cramps, bloating and weight gain Subacute thyroiditis is thought to be caused by a virus. It causes a painful, tender, enlarged thyroid gland. The thyroid becomes inflamed and releases thyroid hormone into the bloodstream; the hyperthyroidism resolves when the viral infection improves

Diagnosis Low TSH, elevated T4 and T3 T3 levels are often disproportionately higher than T4 in hyperthyroidism; T3 measurements may be valuable for evaluating and following patients with this disorder. Thyroid scan may also be recommended to help determine the cause of hyperthyroidism (Graves' disease, toxic nodular goiter, or thyroiditis)

Thyroid Scan Results E. Thyroiditis

Treatment: Anti-Thyroid Drugs Anti-thyroid drugs, such as methimazole and propylthiouracil, work by decreasing how much thyroid hormone the body makes. Both are very effective, but methimazole is preferred because of a greater risk of serious side effects with PTU These medications can be used: As a short term (4-8 weeks) treatment in people with Graves' disease or toxic nodular goiter, before treatment with radioiodine or surgery As a long term (1-2 years) treatment for Graves' disease. The disease goes into remission in about 30% of people, and anti-thyroid drugs can be used to control hyperthyroidism while waiting to see if remission occurs People who have very mild Graves' disease may have as high as a 50-70% chance of remission. It is possible to have a relapse years later, and most people will need to eventually consider permanent treatment with radioactive iodine or surgery Antithyroid drugs have some minor side effects, such as rash, hives, painful joints, fever, and stomach upset. A more serious complication called agranulocytosis (lack of white blood cells) can occur, but this is very rare. PTU has rarely been linked with liver failure.

Treatment: Beta- Blockers Beta-blockers, such as atenolol, are often started as soon as the diagnosis of hyperthyroidism is made While beta-blockers do not reduce thyroid hormone production, they can control many of the symptoms, such as rapid heart rate, tremors, anxiety and heat intolerance Once the hyperthyroidism is under control (with anti- thyroid drugs, surgery or radioactive iodine), the beta-blocker is stopped

Treatment: Radioactive Iodine Destroying the thyroid with radiation, called radioiodine ablation, is a permanent way to treat hyperthyroidism The amount of radiation used is small and does not cause cancer or infertility Radioiodine is given in liquid or capsule form, and works by destroying much of the thyroid; takes ~6-18 weeks People with severe symptoms, older adults and people with heart problems should first be treated with an anti- thyroid drug to control symptoms Most people who take radioiodine develop hypothyroidism and will need to take thyroid hormone supplements for the rest of their lives As with most treatments, there are some risks with radioactive iodine: Sometimes, after apparently successful treatment, the condition returns and further treatment is needed. About 20 percent of people who use radioiodine treatment require a second dose. These people usually have severe hyperthyroidism or a very large goiter. Occasionally, people with Graves' disease find that their eye symptoms worsen after therapy. People who are treated with radioiodine should avoid close physical contact, especially with young children and pregnant women, for three to seven days after treatment because of the possibility of exposing them to low doses of radiation. This can be difficult for parents of young children. You will need to see your doctor or nurse on a regular basis after treatment to have your thyroid hormone levels checked and monitor for hypothyroidism or recurrent hyperthyroidism.

Treatment: Surgery Although surgical removal of the thyroid is a permanent cure for hyperthyroidism, it is used far less often than anti-thyroid drugs or radioactive iodine because of the risks (and expense) associated with thyroid surgery The risks include damage to the nerves of the voice box and parathyroid glands However, surgery is recommended when: A large goiter blocks the airways, making it difficult to breathe. You cannot tolerate anti-thyroid drugs, and you do not want to use radioiodine There is a nodule in the thyroid gland that could be cancerous Most people develop hypothyroidism after surgery and require treatment with thyroid hormone

Hypothyroidism

What is it? Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone It is the most common thyroid disorder

Causes In ~95% of cases, hypothyroidism is due to a problem in the thyroid gland itself and is called primary hypothyroidism Rarely, hypothyroidism is a result of decreased production of thyroid-stimulating hormone (TSH) by the pituitary gland Thyroid problems are more common in women, increase with age and are more common in whites and Mexican Americans than in blacks However, certain medications and diseases can also decrease thyroid function. As an example, HYPOthyroidism can also develop after medical treatments for HYPERthyroidism, such as thyroidectomy (surgical removal of the thyroid) or radioactive iodine treatment (to destroy thyroid tissue)

Symptoms Thyroid hormone normally stimulates the metabolism, and most of the symptoms of hypothyroidism reflect slowing of metabolic processes. General symptoms may include fatigue, sluggishness, weight gain, and intolerance of cold temperatures.

Symptoms Decreased sweating, thick skin, coarse or thin hair, brittle nails Mild swelling around the eyes Slowed heart rate and decreased overall cardiac function leading to fatigue and shortness of breath with exercise Mild high blood pressure and elevated cholesterol Tongue swelling, hoarse voice, and sleep apnea Sleep apnea is a condition in which there is intermittent blockage of the airway while sleeping, causing fitful sleep and daytime sleepiness

Symptoms Constipation Absent or infrequent periods to very frequent and heavy periods Myxedema coma – in people with severe hypothyroidism, trauma, infection, exposure to the cold and certain medications can rarely trigger a life-threatening condition called myxedema coma, which causes a loss of consciousness and hypothermia (low body temperature)

Diagnosis Blood tests – TSH is the most sensitive test because it can be elevated even with small decreases in thyroid function Thyroxine (T4), the main product of the thyroid gland, may also be measured to confirm and assess the degree of hypothyroidism T3 levels are mostly useful in hyperthyroidism. Decreased caloric intake or mild illness can inhibit the conversion of T4 to T3 and lead to transiently low T3 levels. This doesn’t mean that there is a primary thyroid issue. FAQ: Why aren’t you checking my T3 levels?

Treatment Goal of hypothyroidism treatment is to return blood levels of TSH and T4 to the normal range and to alleviate symptoms Treatment for hypothyroidism is thyroid hormone replacement therapy, usually given as an oral form of T4 T4 should be taken 1x per day on an empty stomach (1 hour before eating or 2 hours after). Generic (levothyroxine) and brand-name (Synthroid®, Levoxyl®, Levothroid®, Unithyroid®) formulations are equally effective However, it is preferable to stay on the same type of T4 rather than switch between brand name and/or generic formulations

Treatment If a switch is necessary, a blood test is usually done 6 weeks later to determine if the dose needs to be adjusted. Color-coded tablets can help with dose adjustments. Some clinicians prescribe another form of thyroid hormone, triiodothyronine (T3) in combination with T4. However, since T4 is converted into T3 in other organs, most studies have not shown an advantage of combination T3 & T4 therapy over T4 alone. Patients treated with currently available T3-containing preparations have wide fluctuations in serum T3 concentrations throughout the day due to its rapid gastrointestinal absorption and its relatively short half-life in the circulation (about one day). autoimmune thyroid disease appear to be unusually sensitive to the inhibitory effects of iodide upon its own organification and may fail to escape from the Wolff-Chaikoff effect. Thus, iodide may induce or exacerbate hypothyroidism in patients with Hashimoto's thyroiditis.

Treatment In most cases, symptoms begin to improve within 2 weeks of starting thyroid replacement therapy. However, people with more severe symptoms may require several months of treatment before they fully recover. FAQ: All the chat sites recommend Armour® thyroid. Why don’t you? FAQ: Why can’t I treat my hypothyroidism with iodine? Patients treated with currently available T3-containing preparations have wide fluctuations in serum T3 concentrations throughout the day due to its rapid gastrointestinal absorption and its relatively short half-life in the circulation (about one day). autoimmune thyroid disease appear to be unusually sensitive to the inhibitory effects of iodide upon its own organification and may fail to escape from the Wolff-Chaikoff effect. Thus, iodide may induce or exacerbate hypothyroidism in patients with Hashimoto's thyroiditis.

Q&A Caroline Messer, MD, CCD 914 241-1050 cmesser@mkmg.com