INTRODUCTION Hyperthyroidism, a term for overactive tissue within the thyroid gland, resulting in overproduction overproduction and thus an excess of circulating circulating free free thyroid hormones: hormones: thyroxine thyroxine (T4), trii triiod odot othy hyro roni nine ne (T3) (T3) or both both.. Thyr Thyroi oid d horm hormon one e is impo import rtan antt at a cell cellul ular ar leve level, l, affecting nearly every type of tissue in the body. It functions as a stimulus tometabolism, and is critical to normal function of the cell. Hyperthyroidism, Hyperthyroidism, considered considered as the second second most common common endocrine endocrine disorder. disorder. It res results lts from rom an excessiv sive outp utput of thyr hyroid horm ormones nes due due to abnorma rmal stimulat stimulation ion of the thyroid thyroid gland gland by circulat circulating ing immuno immunoglob globulin ulin.. This disorde disorderr affects affects women eight times more frequently than men and peaks between the second and fourth decades of life. It generally occurs between 20 and 40 years old and is more common in females. PREDISPOSING FACTORS Hyperthyroidism occurs when the thyroid releases too much of its hormones over a short (acute) or long (chronic) period of time. Many diseases and conditions can cause this problem, including: • • • • • •
Getting too much iodine Graves disease (accounts for most cases of hyperthyroidism) Inflammation (thyroiditis) of the thyroid due to viral infections or other causes Noncancerous growths of the thyroid gland or pituitary gland Taking large amounts of thyroid hormone Tumors of the testes or ovaries
CLINICAL MANIFESTATIONS Symptoms • • • • • • • • • • •
Difficulty concentrating Fatigue Frequent bowel movements Goiter (visibly Goiter (visibly enlarged thyroid gland) or thyroid nodules Heat intolerance Increased appetite Increased sweating Irregular menstrual periods in women Nervousness Restlessness Weight loss (rarely, weight gain)
Other symptoms that can occur with this disease:
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Breast development in men Clammy skin Diarrhea Hair loss Hand tremor Weakness High blood pressure Itching - overall Lack of menstrual periods in women Nausea and vomiting Pounding, rapid, or irregular pulse Protruding eyes (exophthalmos) Rapid, forceful, or irregular heartbeat ( palpitations) Skin blushing or flushing Sleeping difficulty
ANATOMY AND PHYSIOLOGY Thyroid Gland The thyroid is one of the largest endocrine glands in the body. This gland is found in the neck inferior to (below) the thyroid cartilage (also known as the Adam's apple in men) and at approximately the same level as the cricoid cartilage. The thyroid controls how quickly the body burns energy, makes proteins, and how sensitive the body should be to other hormones. The thyroid participates in these processes by producing thyroid hormones, principally thyroxine (T4) and triiodothyronine (T3). These hormones regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. Iodine is an essential component of both T3 and T4. The thyroid also produces the hormone calcitonin, which plays a role in calcium homeostasis. The thyroid is controlled by the hypothalamus and pituitary. The gland gets its name from the Greek word for "shield", after the shape of the related thyroid cartilage. Hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid) are the most common problems of the thyroid gland.
Anatomy The thyroid gland is butterfly-shaped organ and is composed of two conelike lobes or wings: lobus dexter (right lobe) and lobus sinister (left lobe), connected with the isthmus. The organ is situated on the anterior side of the neck, lying against and around the larynx and trachea, reaching posteriorly the oesophagus and carotid sheath. It starts cranially at the oblique line on the thyroid cartilage (just below the laryngeal prominence or Adam's apple) and extends inferiorly to the fourth to sixth tracheal ring. It is difficult to demarcate the gland's upper and lower border with vertebral levels as it moves position in relation to these during swallowing. The thyroid gland is covered by a fibrous sheath, the capsula glandulae thyroidea, composed of an internal and external layer. The external layer is anteriorly continuous with the lamina pretrachealis fasciae cervicalis and posteriorolaterally continuous with the carotid sheath. The gland is covered anteriorly with infrahyoid muscles and laterally with the sternocleidomastoid muscle. Posteriorly, the gland is fixed to the cricoid and tracheal cartilage and cricopharyngeus muscle by a thickening of the fascia to form the posterior suspensory ligament of Berry. In variable extent, Zuckerkandl's tubercle, a pyramidal extension of the thyroid lobe, is present at the most posterior side of the lobe. In this region the recurrent laryngeal nerve and the inferior thyroid artery pass next to or in the ligament and tubercle. Between the two layers of the capsule and on the posterior side of the lobes there are on each side two parathyroid glands.
The thyroid isthmus is variable in presence and size, and can encompass a cranially extending pyramid lobe ( lobus pyramidalis or processus pyramidalis), remnant of the thyroglossal duct. The thyroid is one of the larger endocrine glands, weighing 2-3 grams in neonates and 18-60 grams in adults, and is increased in pregnancy The thyroid is supplied with arterial blood from the superior thyroid artery, a branch of the external carotidartery, and the inferior thyroid artery, a branch of the thyrocervical trunk, and sometimes by the thyroid ima artery,branching directly from the aortic arch. The venous blood is drained via superior thyroid veins, draining in the internal jugular vein, and via inferior thyroid veins, draining via the plexus thyroideus impar in the left brachiocephalic vein. Lymphatic drainage passes frequently the lateral deep cervical lymph nodes and the pre- and parathracheal lymphnodes. The gland is supplied by sympathetic nerve input from the superior cervical ganglion and the cervicothoracicganglion of the sympathetic trunk, and by parasympathetic nerve input from the superior laryngeal nerve and there current laryngeal nerve. Physiology The primary function of the thyroid is production of the hormones thyroxine (T4), triiodothyronine (T3), and calcitonin. Up to 80% of the T4 is converted to T3 by peripheral organs such as the liver, kidney and spleen. T3 is about ten times more active than T4. T3 and T4 production and action Thyroxine (T4) is synthesised by the follicular cells from free tyrosine and on the tyrosine residues of the protein called thyroglobulin (TG). Iodine is captured with the "iodine trap" by the hydrogen peroxide generated by the enzyme thyroid peroxidase (TPO) and linked to the 3' and 5' sites of the benzene ring of the tyrosine residues on TG, and on free tyrosine. Upon stimulation by the thyroid-stimulating hormone (TSH), the follicular cells reabsorb TG and proteolytically cleave the iodinated tyrosines from TG, forming T4 and T3 (in T3, one iodine is absent compared to T4), and releasing them into the blood. Deiodinase enzymes convert T4 to T3. Thyroid hormone that is secreted from the gland is about 90% T4 and about 10% T3. Cells of the brain are a major target for the thyroid hormones T3 and T4. Thyroid hormones play a particularly crucial role in brain maturation during fetal development. A transport protein (OATP1C1) has been identified that seems to be important for T4 transport across the blood brain barrier. A second transport protein (MCT8) is important for T3 transport across brain cell membranes. In the blood, T4 and T3 are partially bound to thyroxinebinding globulin, transthyretin and albumin. Only avery small fraction of the circulating hormone is free (unbound) - T4 0.03% and T3 0.3%. Only the free fraction hashormonal activity. As with the steroid hormones and retinoic
acid, thyroid hormones cross the cell membrane andbind to intracellular receptors (α1, α2, β1 and β2), which act alone, in pairs or together with the retinoid Xreceptor astranscription factors to modulate DNA transcription. T3 and T4 regulation The production of thyroxine and triiodothyronine is regulated by thyroidstimulating hormone (TSH), released by the anterior pituitary (that is in turn released as a result of TRH release by the hypothalamus). The thyroid and thyrotropes form a negative feedback loop: TSH production is suppressed when the T4 levels are high, and vice versa. The TSH production itself is modulated by thyrotropinreleasing hormone (TRH), which is produced by the hypothalamus and secreted at an increased rate in situations such as cold (in which an accelerated metabolism would generate more heat). TSH production is blunted by somatostatin (SRIH), rising levels of glucocorticoids and sex hormones (estrogen and testosterone), and excessively high blood iodide concentration. Calcitonin An additional hormone produced by the thyroid contributes to the regulation of blood calcium levels. Parafollicular cells produce calcitonin in response to hypercalcemia. Calcitonin stimulates movement of calcium into bone, in opposition to the effects of parathyroid hormone (PTH). However, calcitonin seems far less essential than PTH, as calcium metabolism remains clinically normal after removal of the thyroid, but not the parathyroids.
LABORATORY AND DIAGNOSTIC EXAMS Physical examination may reveal thyroid enlargement, tremor, hyperactive reflexes, or an increased heart rate. Systolic blood pressure (the first number in a blood pressure reading) may be high. Subclinical hyperthyroidism is a mild form of hyperthyroidism that is diagnosed by abnormal blood levels of thyroid hormones, often in the absence of any symptoms. Blood tests are also done to measure levels of thyroid hormones. • •
TSH (thyroid stimulating hormone) level is usually low T3 and free T4 levels are usually high
This disease may also affect the results of the following tests: • • • • • •
Cholesterol test Glucose test Radioactive iodine uptake T3RU Triglycerides Vitamin B12 (in rare cases)
TREATMENT AND MEDICATIONS How the condition is treated depends on the cause and the severity of symptoms. Hyperthyroidism is usually treated with one or more of the following: •
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Antithyroid medications includes methimazole (Tapazole) or propylthiouracil (PTU) pills These drugs block the amount of thyroid hormone in the blood and make it more difficult for iodine to get into the thyroid gland. Radioactive iodine (which destroys the thyroid and stops the excess production of hormones) Surgery to remove the thyroid
If the thyroid must be removed with surgery or destroyed with radiation, you must take thyroid hormone replacement pills for the rest of your life. Beta-blockers such as propranolol are used to treat some of the symptoms, including rapid heart rate, sweating, and anxiety until the hyperthyroidism can be controlled.
SURGICAL MANAGEMENT Thyroidectomy
Thyroidectomy is a surgical procedure in which all or part of the thyroid gland is removed. The thyroid gland is located in the forward (anterior) part of the neck just under the skin and in front of the Adam's apple. The thyroid is one of the body's endocrine glands, which means that it secretes its products inside the body, into the blood or lymph. The thyroid produces several hormones that have two primary functions: they increase the synthesis of proteins in most of the body's tissues, and they raise the level of the body's oxygen consumption. Purpose All or part of the thyroid gland may be removed to correct a variety of abnormalities. If a person has a goiter, which is an enlargement of the thyroid gland that causes swelling in the front of the neck, the swollen gland may cause difficulties with swallowing or breathing. Hyperthyroidism (over activity of the thyroid gland) produces hypermetabolism, a condition in which the body uses abnormal amounts of oxygen, nutrients, and other materials. A thyroidectomy may be performed if the hypermetabolism cannot be adequately controlled by medication, or if the condition occurs in a child or pregnant woman. Both cancerous and noncancerous tumors (frequently called nodules) may develop in the thyroid gland. These growths must be removed, in addition to some or the entire gland itself.
Demographics Screening tests indicate that about 6% of the United States population has some disturbance of thyroid function, but many people with mildly abnormal levels of thyroid hormone do not have any disease symptoms. It is estimated that between 12 and 15 million people in the United States and Canada are receiving treatment for thyroid disorders as of 2002. In 2001, there were approximately 34,500 thyroidectomies performed in the United States. Females are somewhat more likely than males to require a thyroidectomy. Description A thyroidectomy begins with general anesthesia administered by an anesthesiologist. The anesthesiologist injects drugs into the patient's veins and then places an airway tube in the windpipe to ventilate (provide air for) the person during the operation. After the patient has been anesthetized, the surgeon makes an incision in the front of the neck at the level where a tight-fitting necklace would rest. The surgeon locates and takes care not to injure the parathyroid glands and the recurrent laryngeal nerves, while freeing the thyroid gland from these surrounding structures. The next step is clamping off the blood supply to the portion of the thyroid gland that is to be removed. Next, the surgeon removes all or part of the gland. If cancer has been diagnosed, all or most of the gland is removed. If other diseases or nodules are present, the surgeon may remove only part of the gland. The total amount of glandular tissue removed depends on the condition being treated. The surgeon may place a drain, which is a soft plastic tube that allows tissue fluids to flow out of an area, before closing the incision. The incision is closed with either sutures (stitches) or metal clips. A dressing is placed over the incision and the drain, if one has been placed. People generally stay in the hospital one to four days after a thyroidectomy. Diagnosis/Preparation Thyroid disorders do not always develop rapidly; in some cases, the patient's symptoms may be subtle or difficult to distinguish from the symptoms of other disorders. Patients suffering from hypothyroidism are sometimes misdiagnosed as having a psychiatric depression. Before a thyroidectomy is performed, a variety of tests and studies are usually required to determine the nature of the thyroid disease. Laboratory analysis of blood determines the levels of active thyroid hormones circulating in the body. The most common test is a blood test that measures the level of thyroidstimulating hormone (TSH) in the bloodstream. Sonograms and computed tomography scans (CT scans) help to determine the size of the thyroid gland and location of abnormalities. A nuclear medicine scan may be used to assess thyroid function or to evaluate the condition of a thyroid nodule, but it is not considered a routine test. A needle biopsy of an abnormality or aspiration (removal by suction) of fluid from the thyroid gland may also be performed to help determine the diagnosis.
If the diagnosis is hyperthyroidism, a person may be asked to take anti thyroid medication or iodides before the operation. Continued treatment with anti thyroid drugs may be the treatment of choice. Otherwise, no other special procedure must be followed prior to the operation. Aftercare A thyroidectomy incision requires little to no care after the dressing is removed. The area may be bathed gently with a mild soap. The sutures or the metal clips are removed three to seven days after the operation. Risks There are definite risks associated with the procedure. The thyroid gland should be removed only if there is a pressing reason or medical condition that requires it. As with all operations, people who are obese, smoke, or have poor nutrition are at greater risk for developing complications related to the general anesthetic itself. Hoarseness or voice loss may develop if the recurrent laryngeal nerve is injured or destroyed during the operation. Nerve damage is more apt to occur in people who have large goiters or cancerous tumors. Hypoparathyroidism (underfunctioning of the parathyroid glands) can occur if the parathyroid glands are injured or removed at the time of the thyroidectomy. Hypoparathyroidism is characterized by a drop in blood calcium levels resulting in muscle cramps and twitching. Hypothyroidism (underfunctioning of the thyroid gland) can occur if all or nearly all of the thyroid gland is removed. Complete removal, however, may be intentional when the patient is diagnosed with cancer. If a person's thyroid levels remain low, thyroid replacement medications may be required for the rest of his or her life. A hematoma is a collection of blood in an organ or tissue, caused by a break in the wall of a blood vessel. The neck and the area surrounding the thyroid gland have a rich supply of blood vessels. Bleeding in the area of the operation may occur and be difficult to control or stop. If a hematoma occurs in this part of the body, it may be lifethreatening. As the hematoma enlarges, it may obstruct the airway and cause a person to stop breathing. If a hematoma does develop in the neck, the surgeon may need to perform drainage to clear the airway. Wound infections can occur. If they do, the incision is drained, and there are usually no serious consequences. PROCEDURE: -A thyroid surgery begins with the administration of general anesthesia. Once the anesthesia takes effect, the procedure begins with an incision 2 inches to 4 inches long that stretches horizontally over the thyroid. Based on the tests performed
before the procedure and the appearance of the thyroid, the final determination of how much of the thyroid should be removed is made. -At this point, the portion or portions of the thyroid are removed using a scalpel.Special care is taken not to harm or disturb the parathyroid glands and the vocalcords, both of which rest in the neck near the thyroid. -A biopsy may also be done to examine the tissues of the thyroid, the parathyroid and, in rare cases, nearby lymph nodes. This is done to make sure that the portion of the thyroid that is left, if any, is not diseased. In some cases, the tissue is examined by a pathologist immediately, so that a second surgery to remove a diseased portion of the thyroid is not necessary. -Once the thyroid has been removed and any necessary samples have been taken, the area is examined for bleeding. Once the surgeon is confident that there is no bleeding present, the incision is closed. It may be closed with staples or sutures, and in some cases, a surgical drain may be placed to remove fluid from the area in the days after surgery. Once a sterile bandage is applied to the incision, the surgery is completed. Anesthesia is discontinued and medication is given to wake the patient. The patient is then taken to the recovery room to be closely monitored while the remaining anaesthetic wears off. NURSING MANAGEMENT •Obtain a complete history and asking questions concerning weight, appetite, activity, heat tolerance, and bowel activity •Provide the client with a well-balanced diet high in calories, protein, carbohydrates, and minerals. •Discourage the ingestion of foods that increase peristalsis and thus result in diarrhea, suchas highly seasoned, bulky and fibrous foods. For exophthalmos: •Instruct the client to wear dark eye glasses. •Warn the client to avoid getting dust or dirt in the eyes. •If the eyelids cannot be closed easily or at all, have the client wear a sleeping mask or lightly tape the eyes shut with non-allergic tape. •Elevate the head of the bed at night, and have the client restrict salt intake to relieve edema. MEDICAL MANAGEMENT •Curtail the excessive secretion of TH and prevent and treat complications. •Choice of intervention is based on age, goiter size, and whether the client has other health problems. •The three major forms of therapy are antithyroid medication, radio-iodine therapy, and surgery.
•Iodide, propylthiouracil, and methimazole- major medications used to control hyperthyroidism. •Adrenergic blocking agents may be administered as adjunctive therapy. For exophthalmos: •Diuretics- may alleviate some periorbital edema. •Methyl-cellulose eye drops help reduce eye irritation PROGNOSIS Hyperthyroidism is generally treatable and only rarely is life threatening. Some of its causes may go away without treatment. Hyperthyroidism caused by Graves disease usually gets worse over time. It has many complications, some of which are severe and affect quality of life. POSSIBLE COMPLICATIONS Thyroid crisis (storm), also called thyrotoxicosis , is a sudden worsening of hyperthyroidism symptoms that may occur with infection or stress. Fever, decreased mental alertness, and abdominal pain may occur. Immediate hospitalization is needed. Other complications related to hyperthyroidism include: •
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Heart-related complications including: Rapid heart rate o Congestive heart failure o Atrial fibrillation o Increased risk for osteoporosis, if hyperthyroidism is present for a long time Surgery-related complications, including: Scarring of the neck o Hoarseness due to nerve damage to the voice box o Low calcium level due to damage to the parathyroid glands (located near o the thyroid gland) Treatments for hypothyroidism, such as radioactive iodine, surgery, and medications to replace thyroid hormones can have complications.
