Eval Of Hormones Flashcards
Recommended tests for Cushing’s syndrome
UFC (urinary free cortisol)
Low dose or overnight dexamethasone test
Night-time salivary cortisol
Lab findings for Cushing’s syndrome
CBC- leukocytosis, lymphocytopenia, and decreased eosinophils
CMP- hyperglycemia, hypokalemia, and hypernatremia
Thyroid function- slightly low T3 & TSH
What problem may occur with the 24-hr urinary free cortisol (UFC) that may camouflage a patient with Cushing’s?
Values may appear normal if subjects cortisol is high at night and low during the day
Loose diurnal component while might have avg amount
What test would accurately reflect the diurnal pattern of cortisol?
Normal individuals and patients with pseudo-Cushing states have a pronounced diurnal rhythm with the highest values in the morning and the lowest at night
Patients with Cushing’s syndrome lack their diurnal variation of cortisol
THE DIURNAL PLASMA CORTISOL TEST - great because it reflects this variation
Test that is easier for pt to carry out and still reflects diurnal pattern
Diurnal salivary cortisol test
What does the Overnight dexamethasone test show?
Dexamethasone is a synthetic steroid that will suppress ACTH secretion in normal ppl
This negative feedback system does not work properly in patients with Cushing’s syndrome (cortisol production not suppressed)
Addison’s disease- primary adrenal insufficiency
Lab findings
CMP- hyponatremia, hyperkalemia, hyperglycemia
CBC- normocytic normochromic anemia
Thyroid function- increased thyroid stimulating hormone (TSH)
What does Rapid ACTH stimulation test show?
Pre- blood draw
Administration of synthetic ACTH
30-60 min after, 2 blood samples drawn, one for cortisol and one for aldosterone
For DX of Addison’s both cortisol and aldosterone show minimal or no change in response toACTH
Synacthen test- what does it measure?
Uses synthetic ACTH analogue to trigger adrenal glands to produce cortisol. If this doesn’t happen, know there’s dysfunction in adrenals
Cushing’s syndrome- adrenal function testing
Cortisol- high
ACTH- low
Adrenals themselves overproducing cortisol, pituitary just fine, so down-regulate ACTH
Cushing’s disease- adrenal function testing
Cortisol- high
ACTH- high
Problem is in pituitary - overproducing ACTH with is overstimulating the adrenal glands
Addison’s disease
Cortisol- low
ACTH level- high
Hypopituitarism
Cortisol- low
ACTH level- low
Salivary Adrenal Function Test:
The Preferred Test for Adrenal Fatigue
Use 1 day collection (4 vials) as baseline.
Have patient record S&S, date and time of sample on separate sheet.
If possible, take blood sugar at same time as cortisol level
Growth hormone
Hypothalamus releases GHRH Anterior Pituitary releases GH GH induces release of Insulin-like Growth Factor Triggers = Tissue growth/ repair Increase protein synthesis, growth, etc. Increase GH and release of somatostatin shuts off GHRH and GH release
Quantitative GH
fasting level
isn’t a good test
Provocative test for susptected deficiency
Hypoglycemia causes GH levels to rise
Suppression test
Hyperglycemia suppresses GH (should see suppression in GH to correct for this)
Testing Insulin-like Growth Factor (IGF)
IGF-1 levels reflect average daily levels of GH- easier to test
Low values imply deficiency
High values are seen in acromegaly and gigantism
IGF-1 levels do not fluctuate throughout the day
Regulation of PTH
the dominant regulator of PTH is plasm Ca2+
PTH secretion responds to small alterations in plasma Ca2+ immediately (within seconds)
Function of PTH
PTH acts directly on the bones to stimulate Ca resorption and kidney to stimulate Ca reabsorption
PTH also acts indirectly on intestine by stimulating Vit D synthesis
Hypercalcemia results from
Combined effects of PTH-induced bone resorption, intestinal calcium absorption and renal tubular reabsorption
Hypocalcemia occurs when
there is inadequate response of the Vitamin D-PTH axis to hypocalcemic stimuli
Pseudohypoparathyroidism
Due to defect in PTH receptor-adenylate cyclase complex
- present as hypothyroid patient because parathyroid receptors aren’t working properly
Parathyroid hormone testing
diurnal variation - highest at 2am
levels vary with diet so need fasting specimen
Primary hyperparathyroidism test
high PTH and high calcium levels (due to parathyroid neoplasm)
Secondary hyperparathyroidism test
high PTH and normal/slightly low calcium levels (early chronic renal failure)
Tertiary hyperparathyroidism test
high PTH and high calcium levels (late stage chronic renal failure)
