Acute care handbook for physical therapists (fourth edition) chapter 10 endocrine system

Acute care handbook for physical therapists (fourth edition) chapter 10 endocrine system Acute care handbook for physical therapists (fourth edition) chapter 10 endocrine system Acute care handbook for physical therapists (fourth edition) chapter 10 endocrine system Acute care handbook for physical therapists (fourth edition) chapter 10 endocrine system Acute care handbook for physical therapists (fourth edition) chapter 10 endocrine system

CHAPTER 10 Endocrine System Jaime C Paz Jessika Vizmeg CHAPTER OUTLINE CHAPTER OBJECTIVES General Evaluation of Endocrine Function Thyroid Gland Body Structure and Function Thyroid Tests Thyroid Disorders Pituitary Gland Body Structure and Function Pituitary Tests Pituitary Disorders Adrenal Gland Body Structure and Function Adrenal and Metabolic Tests Adrenal Disorders Pancreatic Disorders Insulin Resistance Metabolic Syndrome Diabetes Mellitus Parathyroid Gland Body Structure and Function Parathyroid Tests Parathyroid Disorders Metabolic Bone Disorders Osteoporosis Osteomalacia Paget’s Disease Physical Therapy Management Goals Guidelines The objectives of this chapter are the following: Provide an understanding of normal functions of the endocrine system, including the thyroid, pituitary, adrenal, and parathyroid glands, as well as the pancreas Describe the clinical evaluation of these endocrine organs Describe the health conditions associated with endocrine system dysfunction and subsequent medical management Provide physical therapy guidelines for working with patients who have endocrine system dysfunction PREFERRED PRACTICE PATTERNS The most relevant practice patterns for the diagnoses discussed in this chapter, based on the American Physical Therapy Association’s Guide to Physical Therapist Practice, second edition, are as follows: • Primary Prevention/Risk Reduction for Skeletal Demineralization: 4A • Impaired Aerobic Capacity/Endurance Associated with Deconditioning: 6B • Primary Prevention/Risk Reduction for Integumentary Disorders: 7A Please refer to Appendix A for a complete list of the preferred practice patterns, as individual patient conditions are highly variable and other practice patterns may be applicable The endocrine system consists of endocrine glands, which secrete hormones into the bloodstream, and target cells for those hormones Target cells are the principal sites of action for the endocrine glands Figure 10-1 displays the location of the primary endocrine glands The endocrine system has direct effects on cellular function and metabolism throughout the entire body, with symptoms of endocrine dysfunction, metabolic dysfunction, or both often mimicking those of muscle weakness.1 Therefore it is important for the physical therapist to carefully distinguish the source (endocrine versus musculoskeletal) of these symptoms to optimally care for the patient For example, complaints of weakness and muscle cramps can both result from hypothyroidism or inappropriate exercise intensity If the therapist is aware of the patient’s current endocrine system status, then inquiring about a recent medication adjustment may be more appropriate than adjusting the patient’s exercise parameters As a group, the prevalence of endocrine and metabolic disorders is approximately 5% of the U.S population.2 An estimated deficit in endocrinologists to meet the demands of the population is projected through the year 2020.2 According to the Centers for Disease Control and Prevention (CDC), approximately 1.7% of the diagnoses of patients admitted to the emergency room were classified as endocrine disorders,3 4.9% of ambulatory care visits are a result of endocrine or metabolic disorders,4 and 5.3% of hospital discharges had endocrine or metabolic disorders listed as a primary diagnosis.5 General Evaluation of Endocrine Function Measurement of endocrine function can be performed by examining (1) the endocrine gland itself, using imaging techniques, or (2) levels of hormones or hormone-related substances in the bloodstream or urine When reviewing the medical record, it is important for the physical therapist to know that high or low levels of endocrine substances can indicate endocrine 243 244 CHAPTER 10    Endocrine System Hypothalamic nuclei TABLE 10-1  Target Sites and Actions of Thyroid Gland Hormones Pituitary gland Hormone(s) Thyroid gland Parathyroid glands Adrenal (suprarenal) glands Target Site(s) Thyroxine (T4) and triiodothyronine (T3) Systemic Thyrocalcitonin Bone Actions Increases metabolic rate; stimulates growth, and development of all cells, particularly of the nervous system; and enhances the effects of catecholamines Inhibits bone resorption Lowers blood levels of calcium Data from Brashers VL, Jones RE: Mechanisms of hormonal regulation In McCance KL, Huether SE, Brashers VL et al, editors: Pathophysiology: the biologic basis for disease in adults and children, ed 6, St Louis, 2010, Mosby, pp 697-726; Hall S: Prescribing in thyroid disease, Nurse Prescribing 8(8):382387, 2010 Pancreas Ovaries (in females) Testes (in males) FIGURE 10-1  Schematic representation of the primary endocrine glands in women and men (Courtesy Marybeth Cuaycong.) dysfunction A common method for assessing levels of hormone is radioimmunoassay (RIA).6 RIA is an immunologic technique for comparing levels of radiolabeled hormone with unlabeled hormone, which compete for binding sites on a given antibody Another method of evaluation, referred to as provocative testing, can be classified into suppression or stimulation tests Stimulation tests are used for testing endocrine hypofunction; suppression tests are useful for evaluating endocrine hyperfunction.7 The most commonly used endocrine tests are discussed in this chapter Clinicians should refer to their particular institution’s laboratory values (generally located in the lab result section of the clinical record) for normal ranges of hormone or hormone-related substances referenced in their setting referred to as the thyroid hormones (Table 10-1) Thyroxine and triiodothyronine require the presence of adequate amounts of iodine to be properly synthesized Therefore dietary deficiencies of iodine can hinder thyroid hormone production The production and secretion of thyroid hormones are regulated by thyrotropin (also called thyroid-stimulating hormone [TSH]), which is secreted from the anterior pituitary gland TSH levels are directly influenced by T4 levels through a negative feedback loop Thyrotropin is further regulated by thyrotropin-releasing hormone, which is secreted from the hypothalamus.8-10 Thyroid Tests Thyroid hormones T4 and T3 circulate throughout the bloodstream bound to proteins or unbound, in which case they are metabolically active by themselves Thyroxine-binding globulin (TBG) is one of the major thyroid transport proteins.9 Serum levels of T4 and T3 are usually measured by RIA Table 10-2 describes the tests used to measure thyroid hormones, and Table 10-3 summarizes other tests used to measure thyroid function   CLINICAL TIP   CLINICAL TIP An imbalance of hormone levels may affect the patient’s tolerance to activity Familiarity with the endocrine tests and values can help the clinician gauge the intended treatment parameters (i.e., type, duration, frequency, and intensity) for the next session(s) Low levels of thyroid hormones T3 or T4 may result in weakness, muscle aching, and stiffness Based on this information, the physical therapist may decide to alter treatment parameters by decreasing the treatment intensity to optimize activity tolerance, minimize patient discomfort, or both Radionuclide testing may also affect a patient’s mobility: patients may be on bed rest or precautions after radionuclide studies The physical therapist should refer to the physician’s orders after testing to clarify the patient’s mobility status Thyroid Gland Body Structure and Function Thyroid Disorders The thyroid gland secretes three hormones: thyroxine (T4), triiodothyronine (T3), and calcitonin, with T4 and T3 commonly Disorders of the thyroid gland result from a variety of causes and can be classified as hyperthyroidism or hypothyroidism CHAPTER 10    Endocrine System 245 TABLE 10-2  Thyroid Hormone Tests Hormone Test Description Normal Value (adults) Serum thyroxine (T4) Serum triiodothyronine (T3) Free thyroxine index Radioimmunoassay (RIA) measurement RIA measurement Direct RIA measurement or indirect calculated measurement Radioisotope and chemical labeling measurement Intravenous administration of TRH to patients TRH augments the function of TSH in patients with hypothyroidism Only performed in difficult diagnostic cases The expected response is a rise in TSH levels 4-12 mcg/dl 40-204 ng/dl 0.93-1.71 ng/ml Thyroid-stimulating hormone (TSH) Thyrotropin-releasing hormone (TRH) 0.4-4.5 µU/ml Normal rise in men and women is 6 µU/ml above baseline TSH levels Normal rise in men older than 40 years is 2 µU/ml above baseline Hypothyroidism is indicated by increased response to TRH Hyperthyroidism is indicated by no response to TRH Data from Sacher RA, McPherson RA, Campos JM, editors: Widman’s clinical interpretation of laboratory tests, ed 11, Philadelphia, 2000, FA Davis, pp 741-823; Cohee L: Endocrinology In Johns Hopkins Hospital, Arcara K, Tschudy M, editors: The Harriet Lane handbook, ed 19, St Louis, 2011, Mosby TABLE 10-3  Thyroid Function Tests Test Description Triiodothyronine resin uptake (RT3U) RT3U qualifies levels of bound versus unbound T4 and T3 and helps to distinguish protein-binding disorders from true thyroid disease Thyroid hormone uptake is high with hyperthyroidism and low with hypothyroidism Used to determine metabolic activity of the thyroid gland Radioactive iodine is administered, and the percentage of total administered radioactive iodine taken up by the thyroid in 24 hours is then calculated Normal radioactive iodine uptake is 10% to 25% Hypothyroidism results in reduced uptake Intravenous administration of radionuclides allows imaging or scanning of particular areas of the thyroid gland Increased or decreased uptake of the radionuclide can help diagnose dysfunction Nodules of the thyroid gland that are palpable or detected by other imaging modalities are indications for ultrasound to help diagnose possible malignancy Fine-needle aspiration of thyroid cells may help diagnose a suspected neoplasm Thyroidal 24-hour radioactive iodine uptake (RAIU) Thyroid imaging or scan Ultrasound Needle biopsy Data from Sacher RA, McPherson RA, Campos JM, editors: Widman’s clinical interpretation of laboratory tests, ed 11, Philadelphia, 2000, FA Davis, pp 786-793; Bastin S, Bolland MJ, Croxson MS: Role of ultrasound in the assessment of nodular thyroid disease, J Med Imaging Radiat Oncol 53;177-187, 2009; McDermott M: Endocrine secrets, ed 5, St Louis, 2009, Mosby, pp 279-282 Hyperthyroidism Hyperthyroidism, or thyrotoxicosis, is primarily characterized by excessive sympathomimetic and catabolic activity resulting from overexposure of tissues to thyroid hormones In addition, it has been reported that hyperthyroidism results in both an increased sympathetic activity with concurrent decreased vagal (parasympathetic) tone.11 Spectral analysis of heart rate variability has been shown to detect these changes and is helpful in determining the severity of hyperthyroidism.11 Heart rate variability is discussed further in Chapter Patients may also present with subclinical hyperthyroidism, which may or may not lead to overt hyperthyroidism Subclinical hyperthyroidism is defined by low TSH levels and normal T3 and T4 levels.12 The most common causes of hyperthyroidism are outlined in Table 10-4 Signs and symptoms of hyperthyroidism include the following8,10,13: • Nervousness, irritation, emotional lability, tremors, insomnia • Fatigue, weakness, increased reflexes • Palpitations, atrial fibrillation, tachycardia • Moist and warm skin, or smooth and velvety skin • Increased perspiration, heat intolerance • Diarrhea, thirst, weight loss despite increased appetite • Reduced menstruation • Lid lag, retraction, or both • Finger nails that grow away from the nail bed, thinning or loss of hair • Thyroid bruit, presence of goiter • Patients may also present with subclinical hyperthyroidism 246 CHAPTER 10    Endocrine System TABLE 10-4  Common Causes of Hyperthyroidism Cause Description Graves’ disease A familial, autoimmune disorder responsible for approximately 80% to 90% of hyperthyroid cases Occurs more commonly in women than men Distinguishing features include diffuse thyroid enlargement, ophthalmopathy (double vision and sensitivity to light), exophthalmos (excessive prominence of the eyes), pretibial myxedema (thickening, redness, and puckering of skin in the front of the tibia), atrial fibrillation, fine hand tremors, and weakness of the quadriceps muscle Inflammation of the thyroid gland can result from an acute bacterial infection, a subacute viral infection, or chronic inflammation with unknown etiology Pain may or may not be present on palpation of the gland Areas of the enlarged thyroid gland (goiter) become autonomous and produce excessive amounts of thyroid hormones Solitary, benign follicular adenomas that function autonomously result in hyperthyroidism if the adenoma nodule is larger than 4 cm in diameter May present as a painless lump in the throat Four types of malignancies in the thyroid gland: papillary carcinoma (most common), follicular carcinoma, anaplastic carcinoma, and medullary carcinoma Ingestion of excessive amounts of thyroid hormone or iodine preparation Can be classified as iatrogenic hyperthyroidism, factitious hyperthyroidism, or iodine-induced hyperthyroidism Thyroiditis Toxic nodular and multinodular goiter Thyroid adenoma Thyroid carcinoma Exogenous hyperthyroidism Data from Woolf N, editor: Pathology, basic and systemic, London, 1998, Saunders, pp 863-873; Mitrou P, Raptis SA, Dimitriadis G: Thyroid disease in older people, Maturitas 70:5-9, 2011 Management of hyperthyroidism primarily includes pharmacologic therapy, which is summarized in Chapter 19, Table 19-42 Surgical management is indicated for patients with large goiters, large “hot” nodules or where other options have been ruled out.14 Surgical options include six different procedures that remove portions or all of the thyroid gland.15 Hypothyroidism Hypothyroidism is the insufficient exposure of peripheral tissues to thyroid hormones It affects growth and development, as well as many cellular processes Primary hypothyroidism is caused by decreased thyroid hormone production by the thyroid gland and accounts for the majority of thyroid disease Secondary hypothyroidism is caused by either pituitary or hypothalamic disease resulting in reduced TSH levels.13 The following are the causes of primary and secondary hypothyroidism13,14: • Congenital maldevelopment, hypoplasia, or aplasia of the thyroid gland • Hashimoto’s thyroiditis (autoimmune inflammation) • Hypopituitarism or hypothalamic disease • Severe iodine deficiency • Thyroid ablation from surgery, radiation of cervical neoplasms, or radioiodine therapy for hyperthyroidism • Drug toxicity (from amiodarone or lithium) General signs and symptoms of hypothyroidism vary according to the degree of thyroid deficiency Signs and symptoms include the following8,10,13: • Lethargy, somnolence, and reduced cognitive function • Constipation and ileus (decreased motility) • Rough, scaly, dry, and cool skin, decreased perspiration, yellowish complexion • • • • • • • Delayed deep tendon reflexes Cold intolerance Weakness, muscle cramps, and aching and stiffness Slow speech, decreased hearing Paresthesia Nonpitting edema of eyelids, hands, and feet Bradycardia with elevated systolic and diastolic blood pressure • Cardiac failure, pericardial effusion • Coma and respiratory failure in severe cases Additional laboratory findings that are associated with hypothyroidism include the following16: • Low glucose and serum sodium levels • Anemia • Elevated levels of cholesterol, creatinine phosphokinase (CKMM), serum myoglobin, lactate dehydrogenase, liver enzymes, homocysteine, and prolactin • Proteinuria Management of hypothyroidism typically includes lifelong thyroid hormone replacement, primarily consisting of generic and brand-name variations of levothyroxine.10,13 A complete list of medications is provided in Chapter 19, Table 19-42   CLINICAL TIP Properly managed hyperthyroidism or hypothyroidism should not affect physical therapy intervention or activity tolerance If the signs or symptoms just mentioned are present during physical therapy evaluation, treatment, or both, then consultation with the medical team is indicated to help differentiate the etiology of the physical findings CHAPTER 10    Endocrine System 247 TABLE 10-5  Target Sites and Actions of Pituitary Gland Hormones Hormone(s) Target Site(s) Action(s) Anterior Lobe Growth hormone Systemic Thyrotropin (thyroid-stimulating hormone) Adrenocorticotropic hormone (ACTH) Thyroid Adrenal cortex Follicle-stimulating hormone Ovaries Testes Ovaries Testes Mammary glands Stimulates body growth, lipolysis, inhibits insulin action on carbohydrates and lipids Stimulates production of thyroid hormones Stimulates production of androgens and glucocorticoids by adrenal cortex Development of follicles and secretion of estrogen Development of seminiferous tubules and spermatogenesis Ovulation, formation of corpus luteum, and secretion of progesterone Secretion of testosterone Stimulates milk production and secretion Luteinizing or interstitial cell–stimulating hormone Prolactin or lactogenic hormone Posterior Lobe Antidiuretic hormone* (also called vasopressin) Oxytocin* Kidney Uterus Breast Controls rate of water excretion into the urine Fluid and electrolyte balance Contraction Expression of milk From Hall JE: Pituitary hormones and their control by the hypothalamus In Guyton and Hall textbook of medical physiology, ed 12, St Louis, 2010, Saunders Elsevier, pp 895-906 *Actually produced in the hypothalamus but stored in the pituitary gland Pituitary Gland Body Structure and Function Hormones secreted by the pituitary gland are responsible for a variety of functions that are summarized in Table 10-5 Secretions of hormones from the pituitary gland are closely regulated by the hypothalamus and by negative feedback from the hormones that are secreted from the pituitary gland.8 Pituitary Tests Individual pituitary hormone levels can be measured (1) by random blood samples; (2) by blood samples before and after the administration of specific releasing substances, such as serum TSH, during a thyrotropin-releasing hormone test (see Table 10-2); or (3) by blood samples before and after the administration of specific stimuli acting directly on the pituitary or via the hypothalamus, such as serum growth hormone (GH), serum cortisol, and plasma adrenocorticotropic hormone (ACTH) Table 10-6 describes common tests of pituitary function Pituitary function can also be evaluated by (1) thyroid function tests, which are an indirect assessment of TSH secretion from the pituitary, and (2) plain x-rays or computed tomography with contrast to highlight a pituitary tumor.17 Pituitary Disorders Dysfunction of the pituitary-hypothalamic system generally results from hypersecretion or hyposecretion of tropic hormones Hypersecretion of pituitary hormones (hyperpituitarism) is most commonly due to adenoma in the anterior lobe (benign tumors).18 Hyposecretion of pituitary hormones (pituitary insufficiency) can result from pituitary disease, diseases affecting the hypothalamus or surrounding structures, or disturbance of blood flow around the hypothalamus and pituitary.19,20 Hyperpituitarism The overproduction of the pituitary hormones GH, ACTH, and antidiuretic hormone (ADH) is discussed next Growth Hormone Overproduction.  Excessive GH secretion is referred to as acromegaly in adults or gigantism in children Excessive GH secretion has been linked primarily to anterior pituitary adenomas and not necessarily to excessive hypothalamic stimulation of the pituitary.20 Clinical manifestations for children with gigantism are characterized by disproportionately long limbs.18 Signs and symptoms of adults with acromegaly include the following20,21: • Enlargement of hands and feet, coarse facial features with furrowed brows • Oligomenorrhea or amenorrhea in women • Paresthesia of hands, carpal tunnel syndrome • Sweating • Headaches • Impotence in men • Diabetes mellitus • Hypertension • Joint pains, osteoarthritis Management of acromegaly may include the following: transsphenoidal surgical resection for microadenoma (treatment of choice in both Europe and the United States) and neurosurgery for macroadenomas.22 Medical therapy consists of GH   CLINICAL TIP Given the multisystem effects in patients with acromegaly, activity progression should proceed cautiously, with a focus on energy conservation, joint protection techniques, and fallprevention strategies 248 CHAPTER 10    Endocrine System TABLE 10-6  Pituitary Hormone Tests Hormone(s) Test Description Growth hormone (GH) Serum level measurement by radioimmunoassay (RIA); normal values for men are to 5 ng/ml; normal values for women are to 10 ng/ml Growth hormone–stimulation test (arginine test or insulin tolerance test) A baseline level of GH is established, then arginine or insulin is administered to the patient, and serial blood draws are performed to measure GH levels GH should normally rise Failure of GH levels to rise significantly may indicate growth hormone deficiency Growth hormone suppression test (glucose load test) A baseline level of GH is established, followed by patient ingestion of a glucose solution Levels of GH are redrawn at timed intervals Normally, glucose inhibits the secretion of GH If GH levels remain high despite the glucose load, then the likelihood of gigantism or acromegaly is increased Plasma ACTH levels are measured by RIA Normal values are 25-100 pg/ml in the morning and 0-50 pg/ml in the evening ACTH-stimulation test (Cortrosyn stimulating test) Indicated for evaluating primary or secondary adrenal insufficiency Cosyntropin (Cortrosyn, a synthetic form of ACTH) is administered to the patient after a baseline level of cortisol is measured ACTH acts to increase cortisol secretion from the adrenal gland Normal results show an increased plasma cortisol level to >20 pg/dl after 30-60 minutes ACTH-suppression test (dexamethasone suppression test) Dexamethasone is administered to the patient to determine ACTH response, which should be a reduction in ACTH levels in non-obese individuals May be used in the diagnosis of Cushing’s syndrome Normal plasma levels of ADH are 2-12 pg/ml if serum osmolality is > 290 mOsm/kg and