Patients with thyroid dysfunctions require risk management before dental procedures

Thyroid dysfunction is the second most common glandular disorder of the endocrine system. The thyroid is the major regulator of metabolism and effects all of the bodily functions. The pituitary gland stimulates the thyroid to produce the hormones thyroxine (T4), triiodothyronine (T3), and ccalcitonin.

Apr 1st, 1996

Cynthia R. Biron, RDH

Thyroid dysfunction is the second most common glandular disorder of the endocrine system. The thyroid is the major regulator of metabolism and effects all of the bodily functions. The pituitary gland stimulates the thyroid to produce the hormones thyroxine (T4), triiodothyronine (T3), and ccalcitonin.

An over or under secretion of hormones of the thyroid gland in the adult patient can be controlled by the use of exogenous hormone, anti-hormone therapy, and thyroidectomy. The onset of thyroid dysfunction may be slow and insidious. The discovery of the hormone dysfunction may be initially suspected by a dental health professional who is conscientious about patient assessment (especially extraoral examinations).

The patient with a thyroid dysfunction, as well as the patient taking medications for thyroid dysfunction, requires proper risk management before considering dental treatment. Patients whose thyroid hormone level is within normal limits are in an euthyroid state. The undersecretion of thyroid hormones means patients are suffering from hypothyroidism. The oversecretion of hormones leads to hyperthyroidism.

The goal of drug therapy for thyroid dysfunction is to restore euthyroid status. Keep in mind that the thyroid gland regulates metabolism and the biochemical activity of most of the tissues of the body. So hyperthyroidism or hypothyroidism presents with characteristic manifestations that can progress to a life-threatening situation if left untreated or improperly managed.

Drugs used in dentistry can interact adversely with high levels of endogenous hormones and normal levels of exogenous thyroid hormones. A thorough investigation of the patient`s medical history, a physical assessment, and a drug history can prevent a life-threatening situation in a patient with a thyroid dysfunction.

Hyperthyroidism (thyrotoxicosis)

Several names are given to the hyperthyroid diseases; most are derived from the names of researchers and physicians who discovered the increased thyroid gland function that is associated with excessive hormone production. Graves` disease (Basedow`s disease in other countries), Plummer`s disease, Parry`s disease, and thyroiditis are such diseases. The diseases are manifested in females between the ages of 20 to 40 in an 8:1 ratio over males.

Thyrotoxicosis is usually revealed by a diffusely enlarged goiter. If it is nodular, many nodules can be felt on palpation. The nodules secrete excessive amounts of the hormone, and the rest of the thyroid tissue is atrophied. It is called a toxic nodular goiter and occurs in long-term thyroid enlargement. Therefore, it is more likely to be found in older patients than the 20 to 40 age range.

Graves` disease is an autoimmune thyroid disorder that presents with the diffuse enlargement of the gland and a presence of antibodies against fractions of the thyroid. It is familial and became more well known to the public when President and Mrs. Bush were diagnosed with the disease. It certainly is not in any way contagious, and it is rather unusual that a husband and wife would have each inherited it from their respective families. The incidence of all types of hyperthyroidism is three out of 10,000 per year.

Recognition of the signs and symptoms of hyperthyroidism is very important in dentistry. The elevated levels of thyroid hormones in these patients make them extremely sensitive to sympathomimetic drugs such as epinephrine, which is used in dentistry as a vasoconstrictor in local anesthesia and retraction cord.

Administration of sympathomimetics can cause the patient to experience a hypertensive crisis, tachycardia, and/or dysrhythmia. These patients are usually resistant to the effects of CNS depressants such as diazepam and other anti-anxiety drugs. The usual treatment for apprehension and stress reduction will not improve the apprehension or nervousness of these patients, particularly if they are undiagnosed or inadequately medicated.

The signs and symptoms of hyperthyroidism at onset may be mild and mistaken for anxiety. The physical manifestations include nervousness, irritability, weight loss (despite normal or excessive food intake), tremors, rapid speech, moist clammy skin, intolerance to heat, elevated vital signs, and uncoordinated movements.

In Graves` disease, a very noticeable sign is exopthalmos (protruding eyeballs). In early stages, only one eye may show lid retraction, or both eyes may have slight lid lag (a bilateral occurrence such as this is less obvious).

In an extraoral examination the thyroid may be enlarged or noticeably palpable. The changes may be unilateral or bilateral, nodular, or not nodular. These patients may experience sensitivity in that area of the neck. They may not be able to tolerate closed collars or anything around the neck.

The enlarged gland may be more visually noticeable when the patient is in a supine position in the dental chair. But in more severely enlarged thyroids, the bulge in the neck is noticeable even when the patient is sitting upright or standing. If a patient presents with an enlarged thyroid and/or a combination of the signs and symptoms of hyperthyroidism, they should be referred to their physician for evaluation.

Patients with dangerously high levels of thyroid hormones may need aggressive therapy to prevent Thyroid Storm (thyroid crisis). Thyroid Storm is extremely rare and manifests itself in less than 2 percent of patients with hyperthyroidism. It usually occurs in patients who have not previously been diagnosed or long-term hyperthyroid patients who have a sudden exaggeration of hyperthyroid symptoms because of unusual stress, illness, or trauma.

The Thyroid Storm manifestations are associated with those of cardiovascular disease such as severe hypertension, tachycardia, dysrhythmia, and hyperpyrexia. This rare medical emergency is life threatening, and the dental team should immediately summon EMS and provide basic life support to the patient until the paramedics arrive.

Hypothyroidism

Insufficient levels of thyroid hormone cause symptoms such as slower metabolic rate, weight gain, lethargy, intolerance to cold, dry and cool skin, and puffiness of the face and eyelids, as well as others. The blood pressure appears to be normal, but the heart rate is slow. Primary hypothyroidism is caused by a defective thyroid gland. Secondary hypothyroidism is caused by failure of the pituitary gland to provide thyroid stimulatin hormone (TSH) to stimulate the thyroid gland for hormone production.

The most common causes of hypothyroidism is Hashimoto`s thyroiditis which is a chronic progressive condition and autoimmune disorder of the thyroid gland. The other common cause is surgical removal of the thyroid gland.

The treatment of thyroid replacement therapy is monitored by following the patient?s TSH level. L-thyroxine (T4) (Synthroid, Levothroid) are some of the drugs of choice. Generic drugs are not recommended since bioavailability varies among manufacturers.

Patients are placed on full replacement doses of thyroid hormone if they have had a thyroidectomy. An exception is the patient who develops coronary artery disease when thyroid hormones increase myocardial oxygen demand. The delicate balance of maintaining euthyroidism and preventing angina and arrhythmias in patients with both diseases is difficult to attain.

Untreated hypothyroidism can progress to a state of depressed metabolic activity known as Myxedema Coma. The disease is extremely rare, occurring in only 0.1 percent of all patients who have hypothyroidism. The manifestations of Myxedema Coma include hypothermia, hypotension, cardiac arrhythmias, and bradycardia followed by death. It is rarely seen in patients under the age of 50 and is usually the cause of death in elderly hypothyroid patients who have not succumbed to associated cardiovascular disease. It is unlikely that Myxedema Coma would occur in the dental office. Treatment for this emergency is basic life support until the arrival of EMS. Hypothyroid patients are extremely sensitive to CNS depressant drugs commonly used in dentistry.

Benzodiazepines, barbiturates, and narcotic analgesics may cause respiratory and cardiac depression in patients with hypothyroidism. The L-thyroxine (T4) hormone replacement drug can be synergistic with sympathomimetic drugs used in dentistry.

Patients with thyroid dysfunction may undergo changes in their hormone levels and should see their physicians regularly to determine if they are in a euthyroid state. Frequent testing is the only way to ascertain that the doses they are taking are correct for their particular condition.

If patients present with a history of thyroid dysfunction, question them thoroughly and consult with their physician before doing any invasive treatment. As with all patients, a thorough extraoral examination that includes palpation of the thyroid gland is extremely important. It is a service that you can provide for your patient that could save his or her life.

This is not a part of the appointment that you can afford to omit to save time. We owe it to our patients to extend care, and, when we do, they have a great deal more respect for us and our profession in general.

Cynthia R. Biron, RDH, is chair of the dental hygiene program at the Tallahassee Community College. She is also a certified emergency medical technician.

Treatment options target hormone replacement

The treatments for hyperthyroidism are either anti-thyroid drugs, radioactive iodine, or thyroidectomy followed by exogenous thyroid hormone replacement.

Anti-thyroid drugs. These drugs interfere directly with thyroid hormone synthesis. The two anti-thyroid drugs (termed thionamides) are Propylthiouracil (PTU) and Methimazole (Tapazole).

Patients taking PTU must be carefully evaluated before surgery or invasive dental treatment. PTU has anti-vitamin K potential and can cause hypoprothrombinemia and bleeding that poses a risk for hemorrhage.

Thionamides may cause a very rare reaction of agranulocytosis (0.5 percent of patients) that can result in oral infections and inadequate wound healing. These post-op complications could be prevented if clinicians carefully research precautions stated in drug reference books.

Radioactive Iodide (RIA) [Sodium Iodide (Iodotope), Sodium Iodide 131]. The administration of RIA is frequently preferred over the risks of thyroidectomy. Capsules and oral solutions of RIA are swallowed, and the RIA is concentrated in thyroid tissue. The radiation injures the cells so that they are incapable of producing thyroid hormones.

With one dose, 80 to 90 percent of patients are cured of hyperthyroidism within two to four months. However, 20 to 50 percent of the patients become hypothyroid and must then be treated for that condition with exogenous thyroid hormone replacement.

Contrary to previous belief, RIA therapy does not cause harmful effects that increase the incidence of malignancy or genetic defects.

Several studies have followed patients and offspring for decades, determining that RIA has not increased the incidence of malignancy in either patients or offspring.

Beta-adrenergic blockers. The hyperthyroid patients` increased sensitivity to circulating catecholamines causes several of the manifestations associated with the disease. Beta-adrenergic blocking agents are used to reduce palpitations, tremors, nervousness, and tachycardia.

Proporanolol (Inderal), atenolol (Tenormin), and nadolol (Corgard) are the drugs of choice in this category for adjunct therapy in hyperthyroidism.

Oral cholecystographic agents. Some radiologic contrast agents used for gallbladder imaging inhibit rapid onset of thyroid hormone synthesis. Sodium ipodate (Orgrafin) or iopanoic acid (Telepaque) produce a dramatic fall in serum T3 concentration.

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