Endocrine System

General Effects of Hormone Action  Regulate the overall metabolic rate and the storage, conversion, and release of energy.  Regulate fluid and electrolyte balance.  Initiate coping responses to stressors.  Regulate growth and development.  Regulate reproduction processes. 

ASSESSMENT/HISTORY  Patients with diseases of the endocrine system commonly report nonspecific complaints.  Commonly, symptoms may reflect changes in general well-being, such as fatigue, weakness, weight change, appetite, sleep patterns, or psychiatric status.

PHYSICAL EXAMINATION  Objective findings may be obvious and related to the patient's complaints or may be silent signs of which the patient is completely unaware.  Thorough physical examination of all body systems, particularly the integumentary, cardiovascular, and neurologic systems, may reveal key findings for endocrine dysfunction

 DIAGNOSTIC

TESTS

Total Thyroxine 

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This is a direct measurement of the concentration of total thyroxine (T4) in the blood, using a radioimmunoassay technique. It is an accurate index of thyroid function when T4binding globulin (TBG) is normal. Low plasma-binding protein states (malnutrition, liver disease) may give low values. High plasma-binding protein values (pregnancy, estrogen therapy) may give high values. It is used to diagnose hypofunction and hyperfunction of the thyroid and to guide and evaluate thyroid hormone replacement therapy.

Free Thyroxine 

Direct measurement of free T4 concentration in the blood using a two-step radioimmunoassay method.

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Accurate measure of thyroid function independent of the variable influence of thyroid-binding globulin levels.

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Used to aid in the diagnosis of hyperthyroidism and hypothyroidism.

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Used to monitor and guide thyroid hormone replacement therapy, particularly with pituitary disease.

Thyroid-Binding Globulin  This measures the concentration of the carrier protein for T4 in the blood. 

Because most T4 is protein bound, changes in TBG will influence values of T4.

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Helpful in distinguishing between true thyroid disease and T4 test abnormalities caused by TBG excess or deficit.

Triiodothyronine  Directly measures concentration of triiodothyronine (T3) in the blood using a radioimmunoassay technique. 

T3 is less influenced by alterations in thyroid-binding proteins.

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Useful to rule out T3 thyrotoxicosis, hyperthyroidism when T4 is normal, and to evaluate effects of thyroid replacement therapy.

T3 Resin Uptake  This is an indirect measure of thyroid function, based on the available protein-binding sites in a serum sample that can bind to radioactive T3.  The radioactive T3 is added to the serum sample in the test tube and will bind with available protein binding sites. The unbound T3 is added to resin for T3 uptake, reflecting the amount of T3 left over because of lack of binding sites.  Estrogen and pregnancy produce an increase in binding sites, thus causing a lowered T3 uptake.

Free Thyroid Index  The free thyroid index is a laboratory estimate of free T4 concentration with calculated adjustment for variations in patient's TBG concentration.

Thyrotropin, Thyroid-Stimulating Hormone 

Direct measure of TSH, the hormone secreted by the pituitary gland that regulates the production and secretion of T4 by the thyroid gland.

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Blood sample is analyzed by radioimmunoassay.

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Preferred test differentiates between thyroid disorders caused by disease of the thyroid gland itself and disorders caused by disease of the pituitary or hypothalamus.

Thyrotropin-Releasing Hormone Stimulation Test  The thyrotropin-releasing hormone (TRH) stimulation test evaluates the patency of the pituitaryhypothalamic axis. 

Its primary use is to distinguish between secondary and tertiary hypothyroidism and evaluate acromegaly.

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A baseline sample is drawn, then TRH is injected I.V. and blood samples are drawn to determine TSH levels at 30, 90, and 120 minutes.

Parathyroid Hormone  Test is a direct measurement of parathyroid hormone (PTH) concentration in the blood, using radioimmunoassay technique.  Results are usually compared with results of total serum calcium to determine likely cause of parathyroid dysfunction.  Range of normal values may vary by laboratory and method.

Serum Calcium, Total  This is a direct measurement of protein-bound and free ionized calcium.  Ionized calcium fraction is best indicator of changes in calcium metabolism.  Results can be affected by changes in serum albumin, the primary protein carrier.  Used to detect alterations in calcium metabolism caused by parathyroid disease or malignancy.

Serum Phosphate  Test measures the level of inorganic phosphorus in the blood.  Alteration in parathyroid function tends to have opposite effects on calcium and phosphorus metabolism.  Used to confirm metabolic abnormalities that affect calcium metabolism.

Plasma Cortisol  This is direct measure of the primary secretory product of the adrenal cortex by radioimmunoassay technique. 

Serum concentration varies with circadian cycle so normal values vary with time of day and stress level of patient (8 a.m. levels typically double that of 8 p.m. levels).

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Useful as an initial step to assess adrenal dysfunction, but further workup is usually necessary.

24-Hour Urinary Free Cortisol Test  Test measures cortisol production during a 24-hour period.  Useful to establish diagnosis of hypercortisolism.  Less influenced by diurnal variations in cortisol.

Adrenocorticotropic Stimulation Test  ACTH stimulates the production and secretion of cortisol by the adrenal cortex. 

Demonstrates the ability of the adrenal cortex to respond appropriately to ACTH.

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This is an important test to evaluate adrenal insufficiency, but may not distinguish primary insufficiency from secondary insufficiency.

Corticotropin Releasing Hormone Stimulation Test  Test measures responsiveness of pituitary gland to corticotropin-releasing hormone (CRH), a hypothalamic hormone that regulates pituitary secretion of ACTH.  Useful to differentiate the cause of excess cortisol secretion when ectopic source of ACTH is suspected.

Urine Vanillylmandelic Acid and Metanephrine  Direct measure of metabolites of catecholamines secreted by the adrenal medulla.  Metanephrine is a more reliable measure of catecholamine secretion.  Preferred method to diagnose pheochromocytoma.

Aldosterone (Urine or Blood)  Direct measure, using radioimmunoassay technique, of aldosterone, a hormone secreted by the adrenal cortex, which regulates renal control of sodium and potassium.  May be measured in the blood or in 24-hour urine collection sample.  Urine test is more reliable because it is less influenced by short-term fluctuations in the bloodstream.  Useful to diagnose primary aldosteronism.

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Serum Growth Hormone Direct radioimmunoassay measurement of human growth hormone (GH), secreted by the anterior pituitary gland; useful to diagnose acromegaly, gigantism, pituitary tumors, pituitary-related growth failure in children or growth hormone deficiency in adults. Because GH secretion is episodic, single fasting samples may not be reliable to detect GH excess or deficiency.

Serum Prolactin  Direct radioimmunoassay measurement of prolactin, secreted by the anterior pituitary gland; helps diagnose pituitary tumors.

Adrenocorticotropic Hormone  Direct measurement of ACTH concentration in the bloodstream by radioimmunoassay technique.  One measure of pituitary gland function useful to provide important information regarding adrenal gland dysfunction.

Insulin Tolerance Test  Useful to diagnose functional hypopituitarism that is caused by pituitary disease or that appears after pituitary surgery. 

Considered the gold standard for diagnosis of GH deficiency.

Water Deprivation Test  Functional test of the adequacy of posterior pituitary secretion of antidiuretic hormone (ADH) and its ability to concentrate urine and to maintain serum osmolality in the face of water deprivation.  Useful to determine the diagnosis and etiology of diabetes insipidus (DI).

Radioactive 131I Uptake  Measures thyroid uptake patterns of iodine as a whole or within specified areas of the gland.  A solution of sodium iodide 131 (131I) is administered orally to the fasting patient.  After a prescribed interval, usually 24 hours, measurements of radioactive counts per minute are taken with a scintillator.

Thyroid Scan  Rapid imaging of thyroid tissue, particularly suspicious nodules, as contrast imaging agent is rapidly taken up by functioning tissue.  Useful to diagnose thyroid carcinoma.  Contrast media is usually administered I.V.  Images can be obtained from gamma counter within 20 to 60 minutes.

STEROID THERAPY  Steroid therapy is a treatment used in some endocrine disorders and in various other conditions. Steroids are hormones that affect metabolism and many body processes.

STANDARDS OF CARE GUIDELINES ENDOCRINE DISORDERS  When caring for a patient with an endocrine disorder, remember that important metabolic functions may be disrupted, such as fluid and electrolyte balance, glucose and protein metabolism, energy production, calcium ionization, blood pressure (BP) control, thermoregulation, cardiac contractility, intestinal peristalsis, and ability of the body to react to stress.

INSULIN SECRETION AND FUNCTION  Insulin is a hormone secreted by the beta cells of the islet of Langerhans in the pancreas.  Small amounts of insulin are released into the bloodstream in response to changes in blood glucose levels throughout the day.  Increased secretion or a bolus of insulin, released after a meal, helps maintain euglycemia.

Through an internal feedback mechanism that involves the pancreas and the liver, circulating blood glucose levels are maintained at a normal range of 60 to 110 mg/dL.  Insulin is essential for the utilization of glucose for cellular metabolism as well as for the proper metabolism of protein and fat. -Carbohydrate metabolism - insulin affects the conversion of glucose into glycogen for storage in the liver and skeletal muscles, and allows for the immediate release and utilization of glucose by the cells. -Protein metabolism - amino acid conversion occurs in the presence of insulin to replace muscle tissue or to provide needed glucose (gluconeogenesis). -Fat metabolism - storage of fat in adipose tissue and conversion of fatty acids from excess glucose occurs only in the presence of insulin. 

Without insulin, plasma glucose concentration rises and glycosuria results.  Absolute deficits in insulin result from decreased production of endogenous insulin by the beta cell of the pancreas.  Relative deficits in insulin are caused by inadequate utilization of insulin by the cell. 

Type 1 Diabetes Mellitus  Type 1 diabetes mellitus was formerly known as insulin dependent diabetes mellitus and juvenile diabetes mellitus.  Little or no endogenous insulin, requiring injections of insulin to control diabetes and prevent ketoacidosis.  Five to 10% of all diabetic patients have type 1.  Etiology: autoimmunity, viral, and certain histocompatibility antigens as well as a genetic component.  Usual presentation is rapid with classic symptoms of polydipsia, polyphagia, polyuria, and weight loss.  Most commonly seen in patients under age 30 but can be seen in older adults.

Type 2 Diabetes Mellitus  Type 2 diabetes mellitus was formerly known as noninsulin dependent diabetes mellitus or adult onset diabetes mellitus.  Caused by a combination of insulin resistance and relative insulin deficiency.  Approximately 90% of diabetic patients have type 2.  Etiology: strong hereditary component, commonly associated with obesity.  Usual presentation is slow and typically insidious with symptoms of fatigue, weight gain, poor wound healing, and recurrent infection.  Found primarily in adults over age 30; however, may be seen in younger adults and adolescents who are overweight.

Prediabetes  Prediabetes is an abnormality in glucose values intermediate between normal and overt diabetes.

1. Impaired Fasting Glucose  A new category adopted by the American Diabetes Association in 1997 and redefined in 2004.  Occurs when fasting blood glucose is greater than or equal to 100 but less than 126 mg/dL.

2. Impaired Glucose Tolerance  Defined as blood glucose measurement on a glucose tolerance test greater than or equal to 140 mg/dl but less than 200 in the 2-hour sample.  Asymptomatic; it can progress to type 2 diabetes or remain unchanged.  May be a risk factor for the development of hypertension, coronary heart disease, and hyperlipidemias.

Gestational Diabetes Mellitus  Gestational diabetes mellitus (GDM) is defined as carbohydrate intolerance occurring during pregnancy.  Occurs in approximately 4% of pregnancies and usually disappears after delivery.  Women with GDM are at higher risk for diabetes at a later date.  GDM is associated with increased risk of fetal morbidity.  Screening for GDM for all pregnant women other than those at lowest risk (under age 25, of normal body weight, have no family history of diabetes, are not a member of an ethnic group with high prevalence of diabetes) should occur between the 24th and 28th weeks of gestation.

Diabetes Associated with Other Conditions  Certain drugs can decrease insulin activity resulting in hyperglycemia -- corticosteroids, thiazide diuretics, estrogen, phenytoin.  Disease states affecting the pancreas or insulin receptors - pancreatitis, cancer of the pancreas, Cushing's disease or syndrome, acromegaly, pheochromocytoma, muscular dystrophy, Huntington's chorea.

DIAGNOSTIC TESTS/ LABORATORY TESTS

Blood Glucose  Fasting blood sugar (FBS), drawn after at least an 8-hour fast, to evaluate circulating amounts of glucose;  postprandial test, drawn usually 2 hours after a well-balanced meal, to evaluate glucose metabolism;  and random glucose, drawn at any time, nonfasting.

Oral Glucose Tolerance Test  The oral glucose tolerance test (OGTT) evaluates insulin response to glucose loading.  FBS is obtained before the ingestion of a 50- to 200-g glucose load (usual amount is 75 g), and blood samples are drawn at ½, 1, 2, and 3 hours (may be 4- or 5-hour sampling).

 GENERAL

PROCEDURES AND TREATMENT MODALITIES

BLOOD GLUCOSE MONITORING  Accurate determination of capillary blood glucose assists patients in the control and daily management of diabetes mellitus.  Blood glucose monitoring helps evaluate effectiveness of medication; reflects glucose excursion after meals; assesses glucose response to exercise regimen; and assists in the evaluation of episodes of hypoglycemia and hyperglycemia to determine appropriate treatment.

INSULIN THERAPY  Insulin therapy involves the subcutaneous injection of immediate-, short-, intermediate-, or long-acting insulin at various times to achieve the desired effect.  Short-acting regular insulin can also be given I.V.

NPH Only (Neutral Protamine Hagedorn)  Used alone only in type 2 diabetes when patients are capable of producing some exogenous insulin as a supplement for better glucose control. 

NPH can also be given twice daily (morning and bedtime) to eliminate afternoon hypoglycemia yet provide nighttime coverage.

NPH/Regular or NPH/Lispro  Short-acting regular insulin or immediate-acting lispro (Humalog) or aspart (Novolog) insulin is added to NPH to promote postprandial glucose control 

Short- or immediate-acting insulin added to morning NPH controls glucose elevations after breakfast.

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Increased blood glucose levels after supper can be controlled by the addition of short- or immediate-acting insulin before supper.

Intensive Insulin Therapy  Designed to mimic the body's normal insulin responses to glucose.  Uses multiple daily injections of insulin.  NPH or ultralente or glargine (Lantus) insulin is used for basal insulin control.  Regular insulin acts as a premeal bolus given 30 minutes before each meal. Lispro or aspart insulin may be used instead of regular and is taken just before eating.  24-hour insulin coverage designed in this way can be flexible to accommodate mealtimes and physical activity.

Combination Oral Agent and Insulin Therapy 

Appropriate only in type 2 diabetes.

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Intermediate-acting insulin (NPH) is given in the evening and an oral sulfonylurea agent in the morning called BIDS therapy (Bedtime Insulin, Daytime Sulfonylurea).

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Combination therapy may also include the use of a thiazolidinedione (pioglitazone [Actos], rosiglitazone [Avandia]), metformin (Glucophage), or other agents.

DIABETES MELLITUS  Diabetes mellitus is a metabolic disorder characterized by hyperglycemia and results from defective insulin production, secretion, or utilization.

Onset is abrupt with type 1 and insidious with type 2. 1. Hyperglycemia  Weight loss, fatigue  Polyuria, polydipsia, polyphagia  Blurred vision 2. Altered Tissue Response  Poor wound healing  Recurrent infections, particularly of the skin

1. Diet  Dietary control with caloric restriction of carbohydrates and saturated fats to maintain ideal body weight.  The goal of meal planning is to control blood glucose and lipid levels

2. Exercise  Regularly scheduled, moderate exercise performed for at least 30 minutes most days of the week promotes the utilization of carbohydrates, assists with weight control, enhances the action of insulin, and improves cardiovascular fitness. 3. Medication  Oral antidiabetic agents for patients with type 2 diabetes who do not achieve glucose control with diet and exercise only

Complications  Hypoglycemia occurs as a result of an imbalance in food, activity, and insulin/oral antidiabetic agent. 

Diabetic ketoacidosis (DKA) occurs primarily in type 1 diabetes during times of severe insulin deficiency or illness, producing severe hyperglycemia, ketonuria, dehydration, and acidosis.

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Hyperosmolar hyperglycemic nonketotic syndrome (HHNKS) affects patients with type 2 diabetes, causing severe dehydration, hyperglycemia, hyperosmolarity, and stupor.

Nursing Diagnoses  Imbalanced Nutrition: More than Body Requirements related to intake in excess of activity expenditures  Fear related to insulin injection  Risk for Injury (hypoglycemia) related to effects of insulin, inability to eat  Activity Intolerance related to poor glucose control  Deficient Knowledge related to use of oral hypoglycemic agents  Risk for Impaired Skin Integrity related to decreased sensation and circulation to lower extremities  Ineffective Coping related to chronic disease and complex self-care regimen

Teaching About Insulin – avoiding lipodystrophy  Assess patient for the signs and symptoms of hypoglycemia.  Treat hypoglycemia promptly with 15 to 20 g of fast-acting carbohydrates. - Half cup (4 oz) juice, 1 cup skim milk, three glucose tablets, four sugar cubes, five to six pieces of hard candy may be taken orally. 

Encourage patient to carry a portable treatment for hypoglycemia at all times.  Between-meal snacks as well as extra food taken before exercise should be encouraged to prevent hypoglycemia.  Encourage patients to wear an identification bracelet or card that may assist in prompt treatment in a hypoglycemic emergency. 

Assess feet and legs for skin temperature, sensation, soft tissue injuries, corns, calluses, dryness, hammer toe or bunion deformation, hair distribution, pulses, deep tendon reflexes.  Use heel protectors, special mattresses, foot cradles for patients on bed rest.  Avoid applying drying agents to skin (eg, alcohol).  Apply skin moisturizers to maintain suppleness and prevent cracking and fissures. 

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Advise the patient who smokes to stop smoking or reduce if possible, to reduce vasoconstriction and enhance peripheral blood flow.

THE END