ATI 8-0 Endocrine Diagnostics

What happens in an excessive secretion of ADH?

- Causes the syndrome of inappropriate antidiuretic hormone (SIADH) which causes the kidneys retain water, urine becomes concentrated, output drops, and extracellular fluid volume is increased.

Deficiency of ADH indicates what diease?

- Diabetes insipidus, which is characterized by the excretion of a large quantity of diluted urine.

What does the posterior pituitary glad secrete?

- Hormone vasopressin (antidiuretic hormone [ADH]) which increases permeability of the renal distal tubules, causing the kidneys to reabsorb water.

Diagnostic tests to evaluate the function of the thyroid and anterior pituitary glands:

- Serum triiodothyronine (T3) - Serum thyroxine (T4) - Serum thyroid stimulating hormone (TSH) - Serum thyrotropin-releasing hormone (TRH) stimulation test - Radioactive iodine uptake (RAIU) - Ultrasounds or scans may also be performed to determine the size, shape, and presence of nodules and masses on these glands.

Purpose of endocrine blood testing:

- Used to determine an excess or lack of a particular hormone in the body. - Some tests stimulate a reaction in the body that will facilitate diagnosis of a particular disorder.

What tests are done to diagnosis pituitary gland disorders?

- Water deprivation test, serum ADH, serum, urine electrolytes and osmolality, and urine-specific gravity.

Complications: Water Deprivation Test

Dehydration can occur due to a decrease in vascular volume. - Nursing Actions XX Monitor the client closely. XX Early indications of dehydration include postural hypotension, tachycardia, and dizziness.

2. A nurse is reviewing the laboratory tests for a client who has suspected hyperthyroidism. An elevation of which of the following values is the most accurate diagnostic indicator that the client is experiencing a hyperthyroid state A. T3 B. VMA C. TSH D. TRH

A. T3 Rationale: A client's T3 increases in a hyperthyroid state, making it a stronger marker for diagnosing hyperthyroidism. TSH and TRH decrease during a hyperthyroid state due to the negative feedback imposed by the hypothalamus when levels of T3 and T4 are high. VMA is a test for pheochromocytoma and reflects the amount of catecholamine byproducts

1. A client asks the nurse why the provider bases the medication regimen on the HbA1c instead of the log of morning fasting blood glucose levels. Which of the following is an appropriate response by the nurse? A. "It measures how well your insulin is regulating your blood glucose between meals." B. "It indicates how well your blood glucose has been regulated over the past 3 to 4 months." C. "It is the first blood test that should be done to diagnose if an individual has diabetes." D. "It will determine if an individual's dose of Regular insulin needs to be adjusted."

B. "It indicates how well your blood glucose has been regulated over the past 3 to 4 months." Rationale: HbA1c measures the client's blood glucose control over the past 120 days, or 3 to 4 months. It is the best indicator of blood glucose over an extended period of time instead of a short period of time, such as between insulin injections.

4. A client is suspected of having primary adrenal insufficiency. Which of the following responses should the nurse anticipate after an intravenous injection of 1.0 mg of ACTH? A. Little or no increase in plasma cortisol B. Significant increase in plasma cortisol C. Decrease in plasma cortisol D. Delayed increase in plasma cortisol

C. Decrease in plasma cortisol A client who has primary adrenal insufficiency does not produce enough aldosterone and cortisol. Therefore, during an ACTH stimulation test, the expected response would be little or no increase in plasma cortisol. A decrease in baseline cortisol level would not be expected, nor would an increase, either immediate or delayed.

Indications for Dexamethasone Suppression Test

Cushing's disease

Adrenal Cortex

Cushing's disease and Cushing's syndrome (hypercortisolism) are characterized by a hyperfunctioning adrenal cortex and an excess production of cortisol. Addison's disease is characterized by hypofunctioning of the adrenal cortex and a consequent lack of adequate amounts of serum cortisol. ◯◯ Diagnostic tests: - Dexamethasone (Decadron) suppression test - Plasma and salivary cortisol - 24-hr urine for cortisol - Serum adrenocorticotropic hormone (ACTH) - ACTH stimulation tests - CT scan and/or an MRI may be performed to determine if there is atrophy of the adrenal glands causing hypofunction.

What does a water deprivation test measure?

Measures the kidneys' ability to concentrate urine in light of an increased plasma osmolarlity and a low plasma vasopressin level. - It is a specialized test that must be performed in a controlled setting, and the client should be observed constantly throughout the test.

Other Tests to Evaluate Adrenal Gland Function:

Plasma and salivary cortisol, 24-hr urine for cortisol, serum ACTH, and ACTH stimulation tests

Nursing Actions: Water Deprivation Test

Preprocedure ■■ Nursing Actions ☐☐ Begin the test between 0700 and 0900 and ensure that someone has the ability to remain with the client throughout the test. ☐☐ Obtain IV access. Intraprocedure ■■ Nursing Actions ☐☐ Place the client in a recumbent position for 30 min, during which the following steps can be performed (The client may sit or stand during voiding and weight determination.) XX Obtain 7 to 10 mL of heparinized blood in an iced tube and send to the laboratory for immediate processing to determine sodium level. XX Ask the client to empty his bladder, record the amount, and send the specimen to the laboratory for immediate processing to determine osmolality. XX Weigh the client to nearest 0.1 kg. Record weight and obtain and record blood pressure and pulse. ☐☐ Initiate a complete fluid restriction and have the client maintain a semirecumbent position except to void if necessary. ☐☐ Repeat the three steps hourly and record the client's symptoms, if there are any. ☐☐ Continue the steps until the serum sodium concentration or osmolality rises above the upper limit of the expected reference range.

Other Tests: Serum ACTH

REF RANGE: Typical early morning values are from 25 to 200 pg/mL, and early evening values are usually from 0 to 50 pg/mL. INTERPRETATION: • ACTH may be elevated with Addison's disease or decreased with Cushing's disease. NURSING ACTION(S): • Serum ACTH is most accurate if performed in the morning.

Ref Range, Interpretation, Nursing Actions for: Serum Electrolytes & Urine Electrolytes & Osmolarity

REF RANGE: Serum • Sodium - 136 to 145 mEq/L • Potassium - 3.5 to 5.0 mEq/L • Chloride - 98 to 106 mEq/L • Magnesium - 1.3 to 2.1 mEq/L Urine • Urine sodium - 75 to 200 mEq/day • Urine potassium - 26 to123 mEq/day (intake dependent) • Urine chloride - 110 to 250 mEq/24 hr • Urine osmolality - 250 to 900 mOsm/kg INTERPRETATION: • Low serum sodium & high urine sodium content are expected w/ SIADH. • Decreased serum osmolality and increased urine osmolality are indicative of SIADH. NURSING ACTION(S): • No pre- or postprocedure care required - serum samples of blood and urine are analyzed for electrolyte components.

Diagnostic Test(s): Triiodothyronine (T3) & Thyroxine (T4)

REF RANGE: • T3 = 70 to 205 ng/dL • T4 = 4.0 to 12.0 mcg/dL INTERPRETATION: • Low and high levels of each indicate hypothyroidism and hyperthyroidism respectively; a high level of T3 is more diagnostic of hyperthyroidism than is T4. NURSING ACTION(S): • No pre- or postprocedure care is required for either test; the laboratory requires a random blood sample.

Ref Range, Interpretation, Nursing Actions for: Serum ADH

REF RANGE: 0 to 4.7 pg/mL INTERPRETATION: Increased serum ADH is indicative of SIADH. NURSING ACTION: • Client should fast & avoid stress for 12 hr prior to the test. • Review medications with the provider as some meds may interfere w/ test. • Blood drawn & transported to the lab w/in 10 min.

Diagnostic Test(s): Thyroid Stimulating Hormone (TSH)

REF RANGE: 0.4 to 6.15 microunits/mL INTERPRETATION: • It stimulates the release of thyroid hormone by the anterior pituitary gland. • TSH may be elevated or decreased, depending on the cause. - An increased value indicates primary hypothyroidism or secondary hyperthyroidism. - A decreased value indicates primary hyperthyroidism (Grave's disease) or secondary hypothyroidism. NURSING ACTION(S): • No pre- or postprocedure care is required; the laboratory requires a random blood sample.

Ref Range, Interpretation, Nursing Actions for: Urine Specific Gravity

REF RANGE: 1.003 to 1.030 INTERPRETATION: • The urine sample is analyzed for specific gravity. • A decrease in urine output and an increase in urinespecific gravity occur as a result of excess production of ADH. NURSING ACTION(S): • This test is usually performed in a laboratory but can be done in the clinical unit using a calibrated hydrometer or a temperature compensated refractometer.

Other Tests: Urinary cortisol

REF RANGE: 10 to 100 mcg/day INTERPRETATION: • Higher levels indicate hypercortisolism. NURSING ACTION(S): • Urinary cortisol is measured during 24-hr urine collection. ◯ The client empties his bladder and then collects all urine excreted during the next 24-hr period. ◯ The urine must be kept in a jug w/ boric acid added and kept on ice. ◯ If the client is receiving spironolactone, this should be held for 7 days prior to the test.

Diagnostic Test(s): Radioactive iodine uptake (RAIU)

REF RANGE: < 35% of injected amount of radioactive iodine (123I) INTERPRETATION: • It measures the amount of 123I that is absorbed by the thyroid gland. • Clients who have hyperthyroidism absorb high amounts (> 35%) of 123I. NURSING ACTION(S): • The client is administered an oral radioactive dose of 123I, and the amount absorbed is measured by a scintillation counter. • This test cannot be done if the client is pregnant or has had another test done that used an iodine-containing dye.

Diagnostic test(s): Fasting blood glucose

REF RANGE: <110 mg/dL INTERPRETATION: • This test is done to determine the client's blood glucose when no foods or fluids (other than water) have been consumed for the past 8 hr. NURSING ACTION(S): • Ensure that the client has fasted (no food or drink other than water) for the 8 hr prior to the blood draw. • Antidiabetic medications should be postponed until after the level is drawn.

Diagnostic test(s): Oral glucose tolerance test (OGTT)

REF RANGE: <140 mg/dL INTERPRETATION: • This test is done to determine the client's ability to metabolize a standard amount of glucose. NURSING ACTION(S): • Instruct the client to consume a balanced diet for the 3 days prior to the test and fast for the 10 to 12 hr prior to the test. • A fasting blood glucose level is drawn at start of the test. • The client is then instructed to consume a specified amount of glucose. • Blood glucose levels are drawn every 30 min for 2 hr. Clients must be assessed for hypoglycemia throughout the procedure.

Other Tests: Salivary cortisol

REF RANGE: A typical salivary cortisol value at midnight is < 2.0 ng/mL. INTERPRETATION: Higher levels indicate hypercortisolism. NURSING ACTION(S): • Salivary cortisol is usually collected at midnight. • A sample of saliva is obtained by placing a salivary cushion pad inside the client's cheek, directly over the salivary gland.

Diagnostic test(s): Glycosylated hemoglobin (HbA1c)

REF RANGE: Guidelines - an HbA1c of 5% or less indicates the absence of DM; an HbA1c of 5.7% to 6.4% indicates pre-DM, and an HbA1c of 6.5% or higher indicates DM. INTERPRETATION: • HbA1c is the best indicator of an avg blood glucose level for the past 120 days. • This test assists in evaluating treatment effectiveness and compliance with the diet plan, medication regimen, and exercise schedule. NURSING ACTION(S): • No pre- or postprocedure care is required. The test requires a laboratory draw of a random blood sample.

Other Tests: ACTH stimulation test

REF RANGE: If no increase in cortisol occurs after administration of ACTH, the test is positive for Addison's disease or hypocortisolism. INTERPRETATION: • ACTH stimulation test determines the functioning of the pituitary gland in relation to stimulating the secretion of adrenal hormones of cortisol. NURSING ACTION(S): • Two consecutive collections of 24-hr urine are used, one prior to and one after the administration of ACTH.

Diagnostic Test(s): Thyrotropin-Releasing Hormone (TRH) stimulation test

REF RANGE: Relative to baseline INTERPRETATION: • It is normal for the TSH to double the baseline value shortly after administration. • If the TSH increases two fold or more above baseline, this finding is indicative of hypothyroidism. NURSING ACTION(S): • The TRH is assessed by giving a bolus of thyrotropin-releasing hormone, and serum concentrations of TSH are assessed at intervals.

Other Tests: Plasma cortisol

REF RANGE: This test varies according to the time of day. Since it has a diurnal pattern, higher levels are present in the early morning, and the lowest levels occur around midnight, or 3 to 5 hr after the onset of sleep. INTERPRETATION: • Diurnal variations are not seen in a client who has Cushing's syndrome. NURSING ACTION(S): • Plasma cortisol is usually collected at midnight.

Interpretation of + water deprivation test:

Test is positive for diabetes insipidus if the kidneys are unable to concentrate urine despite increased plasma osmolality.

Other diagnostic tests for the posterior pituitary gland:

These following tests are performed to diagnose SIADH: - Serum ADH - Serum electrolytes - Urine electrolytes & osmolality - Urine-specific gravity

Indications for water deprivation test:

This test is performed for clients who have a diagnosis of diabetes insipidus. ■■ Should only be conducted if the client's baseline serum sodium level is w/in the expected ref range & urine osmolality is < 300 mOsm/kg H20. ■■ This test should not be performed on clients who have renal insufficiency, uncontrolled DM, hypovolemia of any etiology, or untreated adrenal or thyroid hormone deficiency.

Diagnostic test(s) for Adrenal Cortex: Dexamethasone suppression test

This test is performed to determine if dexamethasone, which is a steroid similar to cortisol, has an effect on cortisol levels. Typically, the client takes a low or high dose of dexamethasone by mouth, and blood is drawn the next morning to determine if cortisol is present. ■■ A low dose of dexamethasone is given to screen a client for Cushing's disease; high doses are given to determine the cause of the disease. ■■ Some medications are withheld and stress is reduced prior to and during testing, as these can affect the outcome of the test results.

3. Which of the following laboratory values should the nurse expect for a client who is producing too much antidiuretic hormone? (Select all that apply.) ____ Low serum sodium ____ High serum potassium ____ Low urine creatinine ____ High urine sodium ____ Decreased urine osmolality ____ Increased serum osmolality ____ Increased urine-specific gravity

__X__ Low serum sodium ____ High serum potassium ____ Low urine creatinine __X__ High urine sodium ____ Decreased urine osmolality ____ Increased serum osmolality __X__ Increased urine-specific gravity Rationale: SIADH causes a client to retain water, creating dilutional hyponatremia with concurrent urinary excretion of sodium. This will be manifested by a low serum sodium, high urine sodium, and increased urine-specific gravity. Serum potassium and urine creatinine should be unaffected.

Diagnostic tests (Adrenal Medulla): Phentolamine blocking test

◯◯ Phentolamine (Regitine), an alpha blocker, is administered to the client. ◯◯ Indications ■■ Diagnosis of pheochromocytoma ◯◯ Interpretation of Findings ■■ A rapid decrease in systolic blood pressure of ≥ 35 mm Hg and diastolic blood pressure of ≥ 25 mm Hg with the administration of phentolamine is diagnostic for pheochromocytoma. ◯◯ Intraprocedure ■■ Nursing Actions ☐☐ Monitor the client's blood pressure

Interpretation of Findings for Dexamethasone Suppression Test

■■ When decreased amounts of ACTH are produced by the pituitary gland, decreased amounts of cortisol are released by the adrenal glands. ■■ When dexamethasone is given to clients who have Cushing's disease, there is no decrease in the production of ACTH and cortisol.

Adrenal Medulla

●● Disorders of the adrenal medulla may result in the hypersecretion of catecholamines, resulting in stimulation of a sympathetic response, such as tachycardia, hypertension, and diaphoresis. ◯ Diagnostic tests: - vanillylmandelic acid (VMA) testing, - the clonidine suppression test, - the phentolamine blocking test.

Carbohydrate Metabolism

●● Dysfunction of carbohydrate metabolism may be caused by insulin deficiency, as in type 1 diabetes mellitus, or insulin resistance, as in type 2 diabetes mellitus, resulting in hyperglycemia. ◯◯ Diagnostic tests to evaluate carbohydrate metabolism include fasting blood glucose, oral glucose tolerance testing, and glycosylated hemoglobin (HbA1c).

Thyroid and Anterior Pituitary Gland

●● Hyperthyroidism and hypothyroidism are conditions in which there are inappropriate amounts of the thyroid hormones triiodothyronine (T3) and thyroxine (T4) circulating. These inappropriate amounts of T3 and T4 cause an increase or decrease in metabolic rate that affects all body systems. ●● The anterior pituitary gland secretes thyroid stimulating hormone (TSH). Hyposecretion of TSH may lead to secondary hypothyroidism, and hypersecretion of TSH may cause secondary hyperthyroidism.

Diagnostic tests (Adrenal Medulla): Clonidine suppression test

◯◯ The client's plasma catecholamines levels are taken prior to and 3 hr after administration of clonidine (Catapres). ◯◯ Indications ■■ Diagnosis of pheochromocytoma ◯◯ Interpretation of Findings ■■ If a client does not have a pheochromocytoma, clonidine suppresses catecholamine release and decreases the serum level of catecholamines (decreases blood pressure). ■■ If the client does have a pheochromocytoma, the clonidine has no effect (no decreased blood pressure). ◯◯ Pre/intraprocedure ■■ Nursing Actions ☐☐ Inform the client about the test. ☐☐ Monitor the client for hypotension. ◯◯ Postprocedure ■■ Client Education ☐☐ Inform the client that tiredness may be a side effect after the test.

Diagnostic tests (Adrenal Medulla): Vanillylmandelic Acid (VMA)

◯◯ VMA testing is a 24-hr urine collection for vanillylmandelic acid (VMA), a breakdown product of catecholamines. Analysis of other urinary catecholamines may also be measured, such as dopamine and normetanephrine. ◯◯ Indications ■■ Diagnosis of pheochromocytoma ◯◯ Interpretation of Findings ■■ Normal VMA is 2 to 7 mg/24 hr. ■■ High VMA levels at rest indicate pheochromocytoma. ◯◯ Preprocedure ■■ Nursing Actions ☐☐ Monitor/instruct the client regarding 24-hr urine collection. Urine is collected for 24 hr (in a container with a preservative) beginning with an empty bladder. ■■ Client Education ☐☐ Caffeine, vanilla, bananas, and chocolate may be restricted for 2 to 3 days before the test. The client may also be asked to hold aspirin and antihypertensive medications. ☐☐ Instruct the client to maintain a moderate level of activity.