Endocrine Labs & Diagnostic Tests Flashcards
What is considered the “Master Gland” of the endocrine system?
The pituitary gland
What hormones are produced by the posterior pituitary?
ADH
Oxytocin
What hormones are produced by the anterior pituitary?
TSH ACTH FSH & LH Growth hormone Prolactin Endorphins
What is the target organ that TSH acts on?
Thyroid
What is the target organ that ACTH works on?
Adrenal cortex
What hormone, released by the hypothalamus, acts on the anterior pituitary?
CRF (corticotropin-releasing factor)
What happens when the HPA axis responds to stress?
Stress triggers the hypothalamus to release CRF –> CRF acts on the anterior pituitary to release ACTH–> ACTH acts on the adrenals (adrenal cortex) to release cortisol into the circulation
What hormone, released by the anterior pituitary, acts on the adrenals?
ACTH (adrenocorticotropic hormone)
Describe the adrenal glands
Glands that sit on each kidney. An outer cortex surrounds the inner medulla.
What is the purpose of ADH (antidiuretic hormone)?
Regulator of “pure” water supply (through excretion or retention)
What is the body’s ADH response to high plasma osmolality?
Increase ADH–> increases pure water retention –> increases blood volume to equalize plasma osmolality
What hormones are secreted by the thyroid?
Thyroxine (T4), triiodothyronine (T3), and calcitonin
What does PTH (parathyroid hormone), made by the parathyroid, regulate in the blood?
Calcium and phosphorous levels
What is the water deprivation test (also called an ADH stimulation test) used for?
It is used to differentiate causes of diabetes insipidus. It is a type of pituitary study
3 causes of diabetes insipidus
- Neurogenic
- Nephrogenic
- Psychogenic polydipsia
How is a water deprivation test (ADH stimulation test) performed?
- ADH (vasopressin) administered exogenously
2. Monitor: urine output, urine specific gravity, & serum osmolality every hour/2 hours during the test
List the adrenal diagnostic tests
- Cortisol, aldosterone, ACTH serum levels
- Urine cortisol (24 hour urine)
- ACTH stimulation & suppression
- CT/MRI
What do cortisol tests evaluate?
Evaluates the status of adrenal cortex function
What are 2 factors that affect serum cortisol levels?
- Diurnal variation (levels are highest in the morning)
2. Stress
What does aldosterone regulate?
Sodium ( and water, since “salt sucks”)
What does a serum aldosterone test assess for?
Hyperaldosteronism
What must the nurse and patient keep in mind when taking an aldosterone level?
The patient needs to maintain whatever position has been assigned for 2 hours. They may be supine or upright. Their position affects the aldosterone level
What are the 2 ACTH tests?
- Serum ACTH
2. ACTH stimulation or suppression tests
What are ACTH stimulation or suppression tests
This is a test that evaluates adrenal function. For an ACTH stimulation test, synthetic ACTH is administered. For an ACTH suppression test, dexamethasone is administered.
What are the thyroid studies?
- TSH, T3, & T4 serum blood tests
- Thyroid ultrasound
- Thyroid scan
- Radioactive iodine uptake
What is the most sensitive test used to evaluate thyroid dysfunction?
TSH (thyroid stimulating hormone) serum level. TSH is secreted by the anterior pituitary.
What do T3 & T4 serum levels help evaluate?
Thyroid function and monitoring of thyroid therapy
Describe the negative feedback cycle of the thyroid gland
T3 & T4 circulate in the blood; when T3 & T4 levels are adequate, the anterior pituitary stops secretion of TSH.
What does a thyroid scan evaluate for?
Nodules in the thyroid
How is a thyroid scan administered?
- Radioactive isotopes are given PO or IV
- Scanner passes over thyroid
- If nodules are benign, a warm spot appears indicating that the nodules uptake the isotope
- If nodules are malignant, a cold spot is seen and indicates that the nodules did not uptake the isotope
Nursing considerations following a thyroid scan
- Reactions to iodine are rare
- Encourage fluids for 24-48 hours to flush kidneys
- If cold spots were noted, a thyroid biopsy is required to confirm malignancy
Why is a radioactive iodine uptake (RAIU) test used?
- Provides a direct measure of thyroid activity
2. Evaluates function of nodules
How is a radioactive iodine uptake (RAIU) test administered?
- Radioactive iodine administered PO or IV
- Uptake is measured at several intervals (2-4 hours and 24 hours)
- Values are expressed as a percentage
* Provides more information than a thyroid scan because a longer time period is being assessed
What studies evaluate pancreatic function?
- Fasting blood glucose
- Casual blood glucose
- HbA1C
- Oral glucose tolerance test
- Urine studies (ketones)
What does HbA1C evaluate?
Indicates AVERAGE glucose level over the past 120 days (3 months). Used for diagnosis and to evaluate effectiveness of interventions (medications or lifestyle modifications)
What is an oral glucose tolerance test (OGTT) used for?
To diagnose gestational diabetes
High urine ketones are associated with what?
Hyperglycemia
What level of urine ketones is a medical emergency?
> 300 mg/dL (patient in DKA)
Random (non-fasting) glucose level that indicates diabetes
≥ 200 mg/dL; especially when also presenting with hyperglycemia symptoms
Fasting plasma glucose (NPO 8+ hours) level that indicates pre-diabetes
100-125 mg/dL
Fasting plasma glucose (NPO 8+ hours) that indicates diabetes
≥ 126 mg/dL
HbA1C suggesting pre-diabetes/increased diabetes risk
5.7-6.4%
HbA1C indicating diabetes
≥ 6.5%
Acceptable HbA1C range for those diagnosed with diabetes
6-8%, target is 7%
