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Lab findings for Cushing's syndrome

CBC- leukocytosis, lymphocytopenia, and decreased eosinophils

CMP- hyperglycemia, hypokalemia, and hypernatremia

Thyroid function- slightly low T3 & TSH

1

Recommended tests for Cushing's syndrome

UFC (urinary free cortisol)
Low dose or overnight dexamethasone test
Night-time salivary cortisol

2

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

3

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

4

Test that is easier for pt to carry out and still reflects diurnal pattern

Diurnal salivary cortisol test

5

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)

6

Addison's disease- primary adrenal insufficiency
Lab findings

CMP- hyponatremia, hyperkalemia, hyperglycemia
CBC- normocytic normochromic anemia
Thyroid function- increased thyroid stimulating hormone (TSH)

7

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

8

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

9

Cushing's syndrome- adrenal function testing

Cortisol- high
ACTH- low

Adrenals themselves overproducing cortisol, pituitary just fine, so down-regulate ACTH

11

Cushing's disease- adrenal function testing

Cortisol- high
ACTH- high

Problem is in pituitary - overproducing ACTH with is overstimulating the adrenal glands

12

Addison's disease

Cortisol- low
ACTH level- high

13

Hypopituitarism

Cortisol- low
ACTH level- low

14

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

15

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

16

Quantitative GH

fasting level
isn't a good test

17

Provocative test for susptected deficiency

Hypoglycemia causes GH levels to rise

18

Suppression test

Hyperglycemia suppresses GH (should see suppression in GH to correct for this)

19

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

20

Regulation of PTH

the dominant regulator of PTH is plasm Ca2+
PTH secretion responds to small alterations in plasma Ca2+ immediately (within seconds)

21

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

22

Hypercalcemia results from

Combined effects of PTH-induced bone resorption, intestinal calcium absorption and renal tubular reabsorption

23

Hypocalcemia occurs when

there is inadequate response of the Vitamin D-PTH axis to hypocalcemic stimuli

24

Pseudohypoparathyroidism

Due to defect in PTH receptor-adenylate cyclase complex
- present as hypothyroid patient because parathyroid receptors aren't working properly

25

Parathyroid hormone testing

diurnal variation - highest at 2am
levels vary with diet so need fasting specimen

26

Primary hyperparathyroidism test

high PTH and high calcium levels (due to parathyroid neoplasm)

27

Secondary hyperparathyroidism test

high PTH and normal/slightly low calcium levels (early chronic renal failure)

28

Tertiary hyperparathyroidism test

high PTH and high calcium levels (late stage chronic renal failure)