Endocrine Studies
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1213 CHAPTER 48 Endocrine System TABLE 48-8 DIAGNOSTIC STUDIES Endocrine System STUDY PURPOSE AND DESCRIPTION* NURSING RESPONSIBILITY Pituitary Studies Blood Studies Growth hormone (GH) (somatotropin) Evaluates GH secretion. Used to identify GH deficiency or GH excess. GH levels are affected by time of day, food intake, and stress. Male: <4 ng/mL (<4.0 mcg/L) Female: <18 ng/mL (<18 mcg/L) Values >50 ng/mL (>50.0 mcg/L) suggest acromegaly. Make sure that patient has been fasting and has not recently been emotionally or physically stressed. Indicate patient fasting status and recent activity level on the laboratory slip. Send blood sample to laboratory immediately. Somatomedin C (insulin-like growth factor 1 [IGF-1]) Evaluates GH secretion. Provides a more accurate reflection of mean plasma concentration of GH because it is not subject to circadian rhythm and fluctuations. Low levels indicate GH deficiency; high levels indicate GH excess. Reference interval: 135-449 ng/mL Overnight fasting is preferred but not necessary. Growth hormone (GH) stimulation Insulin tolerance test: Regular insulin (0.05-0.15 U/kg) given IV and blood drawn at –30, 0, 30, 45, 60, and 90 min for measurement of glucose and GH. Reference interval: GH >5 mcg/L Arginine-GHRH test: GHRH bolus followed by 30-min infusion of L-arginine. Reference interval: GH >4.1 mcg/L Patient must be NPO after midnight. Water is permitted on morning of test. IV access is established for admin- istration of medications and frequent blood sampling. Continually assess for hypoglycemia and hypotension. 50% dextrose and 5% dextrose IV solution should be kept at the bedside in case severe hypoglycemia occurs. Gonadotropins • Follicle-stimulating hormone (FSH) • Luteinizing hormone (LH) Useful in distinguishing primary gonadal problems from pituitary insufficiency. In women, there are marked differences during menstrual cycle and in postmenopausal period. Levels are low in pituitary insufficiency and high in primary gonadal failure. FSH Female: Follicular phase: 1.37-9.9 mU/mL Ovulatory phase: 6.17-17.2 mU/mL Luteal phase: 1.09-9.2 mU/mL Postmenopause: 19.3-100.6 mU/mL Male: 1.42-15.4 mU/mL LH Female: Follicular phase: 1.68-15 IU/L Ovulatory phase: 21.9-56.6 IU/L Postmenopause: 14.2-52.3 IU/L Male: 1.24-7.8 IU/L There is no special preparation of the patient. Only one blood tube is needed for both FSH and LH. Note on the laboratory slip time of menstrual cycle or whether female is postmenopausal. Water deprivation (ADH stimulation) Used to differentiate causes of diabetes insipidus, including central diabetes insipidus (DI), nephrogenic DI, and psycho- genic polydipsia. ADH (vasopressin) is administered. Reference interval: After ADH administration, urine osmolality shows no further increase. In patients with central DI, urine osmolality increases after ADH. In patients with nephrogenic DI, there is no or minimal response to ADH. Caution: Severe dehydration may occur with central or nephrogenic DI during this test. Should only be performed if serum sodium is normal and urine osmolality is <300 mOsm/kg. The test lasts 6 hr, usually from 6 AM to 12 noon. Obtain baseline weight and urine and plasma osmolality. Assess urine hourly for volume and specific gravity. Send hourly samples or urine osmolality. Discontinue test and rehydrate if patient’s weight drops more than 2 kg at any time. Rehydrate with oral fluids. Check orthostatic BP and pulse after rehydration to ensure adequate fluid volume. Radiologic Studies Magnetic resonance imaging (MRI) Examination of choice for radiologic evaluation of the pituitary gland and hypothalamus. Useful in identification of tumors involving the hypothalamus or pituitary. Inform patient of the need to lie as still as possible during the test; explain that tests are painless and noninvasive. Computed tomog- raphy (CT) scan with contrast media Used to detect tumor and size of tumor. Oral and/or IV contrast medium may be used. Inform patient of procedure. Patient must lie still during the procedure. If IV contrast is used, check for iodine allergy. Thyroid Studies Blood Studies Thyroid-stimulating hormone (TSH) (thyrotropin) Measures levels of TSH. Considered the most sensitive diagnostic test used for evaluating thyroid dysfunction. Reference interval: 0.4-4.2 μU/mL (0.4-4.2 mU/L) Explain blood draw procedure to the patient. No specific preparations are necessary. Thyroxine (T 4 ), total Measures total serum level of T 4 . Useful in evaluating thyroid function and monitoring thyroid therapy. Reference interval: 4.6-11.0 mcg/dL (59-142 nmol/L) See above. Continued ADH, Antidiuretic hormone; GHRH, growth hormone–reducing hormone.
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Transcript of Endocrine Studies
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1213CHAPTER 48 Endocrine System
TABLE 48-8 DIAGNOSTIC STUDIESEndocrine System
STUDY PURPOSE AND DESCRIPTION* NURSING RESPONSIBILITYPituitary StudiesBlood StudiesGrowth hormone (GH)
(somatotropin)Evaluates GH secretion. Used to identify GH deficiency or GH
excess. GH levels are affected by time of day, food intake, and stress.
Male: 4.1 mcg/L
Patient must be NPO after midnight. Water is permitted on morning of test. IV access is established for admin-istration of medications and frequent blood sampling. Continually assess for hypoglycemia and hypotension. 50% dextrose and 5% dextrose IV solution should be kept at the bedside in case severe hypoglycemia occurs.
Gonadotropins Follicle-stimulating
hormone (FSH) Luteinizing hormone
(LH)
Useful in distinguishing primary gonadal problems from pituitary insufficiency. In women, there are marked differences during menstrual cycle and in postmenopausal period. Levels are low in pituitary insufficiency and high in primary gonadal failure.
FSHFemale:Follicular phase: 1.37-9.9 mU/mLOvulatory phase: 6.17-17.2 mU/mLLuteal phase: 1.09-9.2 mU/mLPostmenopause: 19.3-100.6 mU/mLMale: 1.42-15.4 mU/mLLHFemale:Follicular phase: 1.68-15 IU/LOvulatory phase: 21.9-56.6 IU/LPostmenopause: 14.2-52.3 IU/LMale: 1.24-7.8 IU/L
There is no special preparation of the patient. Only one blood tube is needed for both FSH and LH. Note on the laboratory slip time of menstrual cycle or whether female is postmenopausal.
Water deprivation (ADH stimulation)
Used to differentiate causes of diabetes insipidus, including central diabetes insipidus (DI), nephrogenic DI, and psycho-genic polydipsia.
ADH (vasopressin) is administered.Reference interval: After ADH administration, urine osmolality
shows no further increase.In patients with central DI, urine osmolality increases after ADH.In patients with nephrogenic DI, there is no or minimal response
to ADH.
Caution: Severe dehydration may occur with central or nephrogenic DI during this test.
Should only be performed if serum sodium is normal and urine osmolality is
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1214 SECTION 10 Problems Related to Regulatory and Reproductive Mechanisms
STUDY PURPOSE AND DESCRIPTION* NURSING RESPONSIBILITYThyroid StudiescontdBlood StudiescontdFree thyroxine (FT4) Measures active component of total T4. Because level remains
constant, considered better indication of thyroid function than total T4.
Reference interval: 0.8-2.7 ng/dL (10-35 pmol/L)
See above.
Triiodothyronine (T3), total
Measures serum levels of T3. Helpful in diagnosing hyperthyroidism if T4 levels are normal.
Ages 20-50: 70-204 ng/dL (1.08-3.14 nmol/L)Ages >50: 40-181 ng/dL (0.62-2.79 nmol/L)
See above.
Free triiodothyronine (FT3)
Measures active component of total T3.Reference interval: 260-480 pg/dL (4.0-7.4 pmol/L)
See above.
T3 uptake (T3 resin uptake)
Indirectly measures binding capacity of thyroid-binding globulin.Reference interval: 24%-34%
See above.
Thyroid antibodies (Ab) Thyroid peroxidase
(TPO) Ab Thyroglobulin Ab Thyroid-stimulating Ab
Measures levels of thyroid antibodies. Assists in the diagnosis of an autoimmune thyroid disease and separates it from thyroiditis. One or more antibody tests may be ordered depending on symptoms.
See above.
Thyrotropin-releasing hormone (TRH) (TRH stimulation)
Assesses anterior pituitary function via secretion of TSH in response to TRH administration.
Reference interval: Baseline TSH double baseline
Patient should discontinue thyroid medications 3-4 wk before test. After TRH administration, blood is drawn at intervals and TSH levels are determined.
Thyroglobulin Identifies the presence of functioning thyroid tissue or thyroid cancer cells; primarily used as a tumor marker for patients being treated for thyroid cancer.
Reference interval:Males: 0.5-53 ng/mLFemales: 0.5-43 ng/mL
Explain blood draw procedure to the patient. No specific preparations are necessary.
Radiologic StudiesUltrasound Evaluates thyroid nodule(s) to determine if fluid-filled (cystic) or
solid tumor.Explain that gel and a transducer will be used over the
neck. The test will last 15 min. No fasting or sedation required.
Thyroid scan and uptake
Scan: Used to evaluate nodules of thyroid. Radioactive isotopes are given orally or IV. Scanner passes over thyroid and makes graphic record of radiation emitted. Normal thyroid scan reveals homogeneous pattern with symmetric lobes. Benign nodules appear as warm spots because they take up radionuclide; malignant tumors appear as cold spots because they tend not to take up radionuclide.
Radioactive iodine uptake (RAIU): Provides direct measure of thyroid activity. Evaluates function of thyroid nodules. Patient is given radioactive iodine either orally or IV. The uptake by the thyroid gland is measured with a scanner at several time intervals such as 2-4 hr and at 24 hr. The values of RAIU are expressed in percentage of uptake.
Reference interval: For 2-4 hr, 3%-19%; for 24 hr, 11%-30%.
Explain procedure to the patient. Check for iodine allergy. Be sure patient understands that radioactive iodine taken orally is harmless. No special preparation is required. Patient should not have supplemental iodine for several weeks before the test. Thyroid medications interfere with uptake test results.
Parathyroid StudiesBlood StudiesParathyroid hormone
(PTH)Measures PTH level in serum. Must be interpreted in terms of
concomitantly drawn serum calcium level.Reference interval: 50-330 pg/mL (50-330 ng/L)
Fasting specimen preferred. Inform patient that blood sample will be drawn. Sample must be kept on ice. Observe venipuncture site for bleeding or hematoma formation.
Calcium (total) Used to detect bone and parathyroid disorders. Hypercalcemia can indicate primary hyperparathyroidism, and hypocalcemia can indicate hypoparathyroidism.
Reference interval: 8.6-10.2 mg/dL (2.15-2.55 mmol/L)
Inform patient that blood sample will be drawn. Observe venipuncture site for bleeding or hematoma formation.
Calcium (ionized) Free form of calcium unaffected by variable serum albumin levels.Reference interval: 4.64-5.28 mg/dL (1.16-1.32 mmol/L)
See above.
Phosphate Measures inorganic phosphorus. levels indicate primary hypoparathyroidism or secondary causes (e.g., renal failure); levels indicate hyperparathyroidism. Phosphorus and calcium levels are inversely related.
Reference interval: 2.4-4.4 mg/dL (0.78-1.42 mmol/L)
Fasting preferred. Inform patient that blood sample will be drawn. Observe venipuncture site for bleeding or hematoma formation.
TABLE 48-8 DIAGNOSTIC STUDIEScontdEndocrine System
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1215CHAPTER 48 Endocrine System
STUDY PURPOSE AND DESCRIPTION* NURSING RESPONSIBILITYParathyroid StudiescontdRadiologic StudiesParathyroid scan Uses radioactive isotopes that are taken up by cells in
parathyroid glands to obtain an image of the glands and any abnormally active areas. Assists in identifying the number and location of parathyroid glands.
Inform the patient that certain foods and medications need to be restricted for a week before the test, including thyroid medications and foods containing iodine.
Adrenal StudiesBlood StudiesCortisol (total) Measures amount of total cortisol in serum and evaluates status
of adrenal cortex function.Reference interval: 5-23 mcg/dL (138-635 nmol/L) at 8 AM,
3-16 mcg/dL (83-441 nmol/L) at 4 PM
Cortisol has diurnal variationlevels are higher in morning than in evening. Sample should be drawn in morningevening samples may also be ordered.
Mark time of blood draw on laboratory slip. Patient anxiety should be minimized.
Aldosterone Used to assess for hyperaldosteronism.Reference interval: 7-30 ng/dL (0.19-0.83 nmol/L) (upright
posture) and 3-16 ng/dL (0.08-0.44 nmol/L) (supine position)
Usually morning blood sample is preferred. Indicate patient position (supine, sitting, standing) during venipuncture.
Adrenocorticotropic hormone (ACTH) (corticotropin)
Measures plasma level of ACTH. Although ACTH is a pituitary hormone, it controls adrenal cortex secretion, thus helps to determine if underproduction or overproduction of cortisol is caused by dysfunction of the adrenal gland or pituitary gland.
Reference interval: morning:
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STUDY PURPOSE AND DESCRIPTION* NURSING RESPONSIBILITYPancreatic StudiesBlood StudiesFasting blood glucose
(FBG)Measures circulating glucose level.Reference interval: 70-99 mg/dL (3.9-5.5 mmol/L)
Patient should fast for at least 4-8 hr. Water intake is permitted. If patient has an IV infusion containing dextrose, test is not considered valid.
Oral glucose tolerance test (OGTT)
Used to diagnose diabetes mellitus, especially if FBG is equivocal. Patient drinks 75 g of glucose; samples for glucose are drawn at baseline and at 30, 60, and 120 min.
Reference interval:
