ATI Unit 12, Endocrine - Diagnostic Tests

Question 1

what are the category of endocrine diagnoses that a nurse needs to know?

Answer 1

1) posterior pituitary gland
2) adrenal cortex
3) adrenal medulla
4) metabolism of carbs
5) thyroid and anterior pituitary glands

Question 2

what hormone does the posterior pituitary gland secrete? what does this hormone do?

Answer 2

vasopressin or ADH , causes water and salt retention (can increase blood volume for example)

Question 3

what does ADH deficiency cause? ADH oversecretion?

Answer 3

a) deficiency -> causes diabetes insipidus which is characterized by extrection of a large quantity of diluted urine
b) excessive causes syndrome of inappropriate ADH or SIADH, kidneys retain water and urine becomes concentrated, output decreases and ECF volume is increased

Question 4

what are the diagnostic tests for the posterior pituitary gland?

Answer 4

1) water deprivation test
2) serum ADH
3) serum and urine electrolytes and osmolatlity
4) urine-specific gravity

Question 5

what is the water deprivation test?

Answer 5

• measures renal ability to concentrate urine in light of an increased plasma osmolality and low plasma vasopressin level

Indications:

a) performed on clients with diabetes insipidus
b) only conduct if client’s baseline serum Na+ level is within expected reference range and osmolality of urine is below 300 mOsm/kg H2O
c) don’t perform on clients with renal insufficiency, uncontrolled DM, hypovolemia, or untreated adrenal or thyroid hormone deficiency

Interpretation of findings
- is pos for diabetes insipidus of kidneys are unable to concentrate urine despite increased plasma osmolality

Question 6

water deprivation test procedure

Answer 6

Pre

a) avoid smoking, caffeine, alcohol prior to test
b) begin by witholding fluids for 8-12 hours or until 3% to 5% of body weight is lost, ensure someone remains with cleint during test
c) obtain IV access

Intra

a) place client in a recumbent position for 30min during which following steps can be performed (client can sit or stand during voiding/weighing)
- obtain 7-10 ml of heparinized blood in iced tube for lab to process for Na+ level
- ask client to empty bladder, record amount, send to lab to determine osmolality
- weight client to nearest tenth of a kilo (0.1kg), record weight and obtain BP/pulse
b) initiate complete fluid restriction and have client maintain semi-fowler’s except when voiding
c) repeat three step (weight, measure urine, obtain serum) hourly and record any findings
d) continue steps until serum Na+ or osmolality rises above upper limit of expected reference range

Post/Complications
- dehydration can occur due to a decrease in vascular volume -> monitor for sign
SIGNS: postural hypotension, tachy, dizziness

Question 7

Values for serum ADH

Answer 7

Normal reference: 1-5 pg/mL
Interpretation: increased serum ADH indicative of SIADH

Nursing Actions (NAs): 1) client fast and avoid stress for 12 hr prior to test 2) some meds may interfere 3) blood obtained and given to lab within 10 min

Question 8

values for serum electrolytes

Answer 8

Normal: 
Na+ 136-145
K+ 3.5 - 5.0
Cl- 98-106
Mg2+ 1.3-2.1

Interpretations: low serum Na+ and high urine Na+ are expected with SIADH
- decreased serum osmolality and increased urine osmolality are indicative of SIADH

Question 9

values for urine electrolytes and osmolality

Answer 9

Normal
urine sodium: 75-200 mEq/day
urine K+: 26-123/day (intake dependent)
urine Cl - 110-250/24hours
urine osmolality - 200 to 800 mOsm/kg

Interpretation: look at serum electrolytes

Question 10

values for urine specific gravity

Answer 10

normal: 1.010 to 1.025

Interpretation: decreas in output and increase in specific gravity occurs as a result of excess ADH

NAs: test usually performed in lab but can be done in clinical unit using a calibrated hydrometer or temperature-compensated refractometer

Question 11

hyperfunctioning of the adrenal cortex characterizes what two disease? what hormone is producted?

Answer 11

Cushing’s disease and Cushing’s syndrome, characterized by an excess production of cortisol (also called hypercortisolism); hypofunctioning characterizes Addison’s disease which lack serum cortisol

Question 12

what tests are run for the adrenal cortex?

Answer 12

1) dexamethasone (Decadron) suppression test
2) plasma and salivary cortisol
3) 24-hr urine for cortisol
4) serum adrenocorticotropic hormone (ACTH) and ACTH simulation tests

5/6) CT scan or MRI to determine if there is atrophy of adrenal glands

Question 13

the dexamethasone suppression test

Answer 13

• test performed if dexamethasone (steroid similar to cortisol) has an effect on cortisol levels
• usually client takes a dose of dexamethasone by mouth and blood sample is obtained next morning to determine if cortisol is present

Notes:
low dose dexamethasone given -> screens for Cushing’s disease, high doses are given to determine the cause of the disease

Indications: Cushing’s disease

Interpretations:

• when decreased amounts of ACTH produced by pituitary gland, decreased amounts of cortisol are released by adrenal gland
• when dexamethasone is given to client’s who have Cushing’s disease, there is no decrease in production of ACTH and cortisol

Question 14

Values for plasma cortisol, salivary cortisol, urinary cortisol, serum ACTH, and ACTH stimulation tests

Answer 14

1) plasma cortisol
Normal: cortisol varies in day, b/c has a diurnal (daily) pattern, higher levels present in early morning and lowest levels around midnight or 3-5 hours after onset of sleep

Interpretations: durnal variations not seen in client with Cushing’s

NA: plasma cortisol usually collected at midnight

2) salivary cortisol
Normal: salivary cortisol at midnight usually less than 2.0 ng/mL
Interp: higher levels indicate hypercortisolism
NAs: 1) usually collected at midnight 2) sample obtained by placing salivary cushion pad inside the client’s cheek, directly over the salivary gland

3) urinary cortisol
Normal: 10-100 mcg/day
Interp: higher levels indicate hypercortisolism
NAs: urinary cortisol measured during 24-hr urine collection
a) client empties his bladder and then collects all urine excreted during next 24-hr period
b) urine kept in jug with boric acid added and kept on ice
c) if taking spironolactone, should be witheld 7 days prior to test

4) serum ACTH
normal: typical early morning values are 25-200 pg/mL and early evening values usually 0-50
Interp: ACTH poss elevated with Addison’s or decreased with Cushing’s
NAs: serum ACTH most accurate if performed in morning

5) ACTH stimulation test
Normal: if no increase in cortisol after admin of ACTH then pos for Addison’s disease or hypocortisolism

Interp: ACTH stimulation test determines functioning of pit gland in relation to stimulating secretion of adrenal hormones of cortisol
NAs: 2 consecutive 24 hr urine, one prior and one after admin of ACTH

Question 15

what do disorders of the adrenal medulla do?

Answer 15

cause hypersecretion of catecholamines, resulting in stimulation of a sympathetic response such as tachy, HTN and diaphoresis

Question 16

what are the tests for adrenal medulla

Answer 16

1) vanillylmandelic acid (VMA) testing
2) clonidine suppression test
3) phentolamine blocking test

Question 17

what is VMA testing

Answer 17

• a 24hr urine collection for vanillylmandelic acid (VMA), a breakdown product of catecholamines; analysis of urinary catecholamines like dopamine and normetanephrine may also be used

Indications: diagnosis of pheochromoctoma
Interp: expected reference range for VMA is 2-7 mg/24hours
–> elevated VMA levels at rest indicate pheochromocytoma

Pre
NA: empty bladder then collect, kept in container with a preservative
Education: caffeine, vanilla, bananas, and chocolate may be restricted 2-3 days before the test; possibly withold aspirin and antiHTN meds; instruct client to maintain a moderate level of activity

Question 18

what is a clonidine suppression test

Answer 18

• client’s plasma catecholamine levels are taken prior to and 3 hr after admin of clonidine (Catapres)
  Indications: pheochromocytoma

Interp: if doesn’t have a pheochromocytoma, clonidine suppresses catecholamine release and decreases serum level of catecholamines (decreases BP)
- if does have pheochromocytoma, clonidine has no effect (no decreased BP)

Pre/Intra
NAs: monitor for hypotension

Post

Education: inform client that fatigue may occur after test

Question 19

what is the phentolamine blocking test

Answer 19

• phentolamine (Regitine) an alpha blocker is administered
  Indications: pheochromocytoma

Interp: rapid decrease in SBP of > or = 35 mmHg and DBP of >= 25mmHg with admin of phentolamine is diagnostic for pheochromocytoma

Intra
NA: monitor BP

Question 20

carbohydrate metab dysfunction may be caused by what?

Answer 20

1) insulin deficiency as in DM1

2) insulin resistance as in DM2 resulting in hyperglycemia

Question 21

what are the diagnostic tests to evaluate carb metab

Answer 21

1) fasting blood glucose
2) oral glucose tolerance testing
3) glycosylated hemoglobin (HbA1c)

Question 22

Numbers for carb metab tests

Answer 22

1) fasting blood glucose
Normal: less than 110 mg/dL
Interp: determines blood glucose when no foods or fluids (other than water) have been consumed for past 8hr
NAs: ensure client has fasted, na but water for 8 hr prior to blood sample
- antidiabetic meds should be postponed until after level is drawn

2) oral glucose tolerance test
Normal: less than 140mg/dL
Interp: determines ability to metabolize a standard amount of glucose

NAs

• consume balanced diet 3 days prior to test and fast for 10-12 hours before
• fasting blood glucose level is obtained at start
• client consumes specified amount of glucose
• blood samples obtained q30min for 2 hours, MUST be assessed for hypoglycemia throughout procedure

3) glycosylated hemoglobin (HbA1c)
Normal: HbA1c of 5% or less indicates absence of DM; HbA1c of 5.7% to 6.4% indicates prediabetes mellitus, and HbA1c of 6.5% or higher indicates DM

Interp: HbA1c is best indicator of an average blood glucose level for past 120 days
- also can tell about compliance/effectiveness of diet, meds, and exercise

NAs: na, requires random blood sample

Question 23

what are conditions of problems with the thyroid and anterior pituitary gland?

Answer 23

thyroid
hyperthyroidism and hypothyroidism - wrong amounts of thyroid hormones triiodothyronine (T3) and thyroxine (T4) in circulation; can affect all systems/cause metab effects

anterior pituitary gland - secretes thyroid stimulating hormone (TSH)

• hyposecretion of TSH may lead to secondary hypothyroidism
• hypersecretion of TSH may cause secondary hyperthyroidism

Question 24

tests to evaluate the thyroid and anterior pituitary glands

Answer 24

1. T3 and T4
Normal Range: T3 - 70-205; T4 - 4.0-12.0
Interpretation
- low and high levels of each indicate hypothyroidism and hyperthyroidism (high level of T3 diagnoses hyperthyroidism more readily)
- random blood sample no pre/post care

2. TSH
   Normal: 0.3 to 5.0 microunits/mL
   Interpretation stimulates release of thyroid hormone by the anterior pituitary gland
   - TSH may be elevated or decreased, increase = primary hypothyroidism or secondary hyperthyroidism; decreased = primary hyperthyroidism (Grave’s disease) or secondary hypothyroidism
   - no pre/post
3. RAIU = radioactive iodine uptake (measures amount of idione absorbed by thyroid gland; clients with hyperthyroidism absorb high amounts)
   - client given PO radioactive dose of I, cannot be done if pregnant or another test using I was done