Lab med - Pituitary and Adrenal glands Flashcards
(40 cards)
1
Q
Purpose of ACTH
A
determine cause of hypercortisolism and hypocortisolism
2
Q
Purpose of serum cortisol
A
- discriminate between primary and secondary adrenal insufficiency
- differentiate diagnosis of Cushing syndrome
3
Q
Purpose of 24 hour free cortisol/cortisone
A
- Screening test for Cushing syndrome (hypercortisolism)
- Assist in diagnosing acquired or inherited abnormalities of 11-beta-hydroxy steroid dehydrogenase (cortisol or cortisone ratio)
- Dx of pseudo-hyperaldosteronism due to excessive licorice consumption
- Limited usefulness in eval of adrenal insufficiency
4
Q
Purpose of late night salivary cortisol
A
- Screening test for Cushing syndrome (hypercortisolism)
- Dx of Cushing syndrome in pts presenting with sx or signs suggestive of the disease
5
Q
Purpose of overnight low dose dexamethasone suppression test (LDST)
A
Quick screening for nonsuppressible cortisol production and subclinical or clinical Cushing’s syndrome
6
Q
Purpose of growth hormone
A
- Dx of acromegaly, assessment of treatment efficacy
- Dx of human growth hormone deficiency (done in conjunction with GH stimulation test)
7
Q
Purpose of IGF-1
A
- Evaluation of growth disorders
- Evaluation of growth hormone deficiency or excess in children and adults
- Monitoring of recombinant human growth hormone treatment
- Follow-up of individuals with acromegaly and gigantism
8
Q
Purpose of plasma aldosterone
A
- Investigation of primary aldosteronism (eg, adrenal adenoma/carcinoma and adrenal cortical hyperplasia) and
- Investigation of secondary aldosteronism (renovascular disease, salt depletion, potassium loading, cardiac failure with ascites, pregnancy, Bartter syndrome)
9
Q
Purpose of renin activity
A
- Investigation of primary aldosteronism (eg, adrenal adenoma/carcinoma and adrenal cortical hyperplasia) and
- Investigation of secondary aldosteronism (renovascular disease, salt depletion, potassium loading, cardiac failure with ascites, pregnancy, Bartter syndrome)
- Not useful for determination of plasma renin concentration
10
Q
Purpose of prolactin
A
- Aid in eval of pituitary tumors, amenorrhea, galactorrhea, infertility, hypogonadism
- Monitor therapy of prolactin-producing tumors
11
Q
Purpose of testosterone (8)
A
- Evaluation of men with symptoms or signs of possible hypogonadism, such as loss of libido, erectile dysfunction, gynecomastia, osteoporosis, or infertility
- Evaluation of boys with delayed or precocious puberty
- Monitoring testosterone replacement therapy
- Monitoring antiandrogen therapy (eg, used in prostate cancer, precocious puberty, treatment of idiopathic hirsutism, male-to-female transgender disorders, etc.)
- Evaluation of women with hirsutism, virilization, and oligoamenorrhea
- Evaluation of women with symptoms or signs of possible testosterone deficiency
- Evaluation of infants with ambiguous genitalia or virilization
- Diagnosis of androgen-secreting tumors
12
Q
Purpose of serum DHEAS
A
- Dx and ddx of hyperandrogenism (in conjunction with msrmt of other sex steroids)
- Adjunct in dx of congenital adrenal hyperplasia
- Dx and ddx of premature adrenarche
13
Q
Purpose of metanephrines (fractionated, free, plasma)
A
Screening test for presumptive dx of catecholamine-secreting pheochromocytomas or paragangliomas
14
Q
Purpose of 24-hour urine metanephrines and catecholamines
A
- First and second order screening test for presumptive dx of catecholamine-secreting pheochromocytomas and paragangliomas
- Confirms positive plasma metanephrine results
15
Q
What disorders are associated with hypercortisolism
A
- Cushing syndrome
- Cushing disease (pituitary ACTH-producing tumor)
- Ectopic ACTH-producing tumor
- Ectopic CRH
- Adrenal cortisol-producing tumor
- Adrenal hyperplasia (non-ACTH dependent, autonomous cortisol-producing adrenal nodules)
16
Q
What disorders are associated with hypocortisolism
A
- Addison disease – primary adrenal insufficiency
- Secondary adrenal insufficiency
- Pituitary insufficiency
- Hypothalamic insufficiency
- Congenital adrenal hyperplasia – defects in enzyme involved in cortisol synthesis
17
Q
How to interpret elevated ACTH in patient with hypocortisolism
A
indicates primary adrenal insufficiency
18
Q
How to interpret suppressed ACTH level in pt with hypercortisolism (Cushing)
A
Consistent with cortisol-producing adrenal adenoma or carcinoma, primary adrenal micronodular hyperplasia, or exogenous corticosteroid use
19
Q
What interferes with ACTH assay?
A
glucocorticoids
20
Q
What should pt not take before an ACTH lab test?
A
biotin
21
Q
What are the expected ACTH and cortisol levels in a pt with primary adrenal insufficiency?
A
- ACTH levels are increased
- cortisol is decreased
22
Q
What are the expected ACTH and cortisol levels in a pt with secondary adrenal insufficiency?
A
Both ACTH and cortisol are decreased
23
Q
Identify the expected results of a 24-hour urinary excretion of cortisol in a person with Cushing syndrome
A
Increased 24 hour urinary excretion of cortisol or cortisone
24
Q
Identify the factors that affect a 24-hour urinary excretion of cortisol (5)
A
- Acute stress, alcoholism, depression, many drugs can obliterate normal diurnal variation, affect response to suppression/stimulation tests, and increase baseline levels
- Improper collection – missed morning collection may result in false-negative, extra morning collection may result in false-positive
- Renal disease: decreased clearance may cause falsely low values
- Pregnancy: values may be elevated twice normal range
- Exogenous Cushing syndrome: dt ingestion of hydrocortisone will not have suppressed cortisol/cortisone values
25
what is the preferred screening test for Cushing syndrome
24-hour UFC excretion
26
Why is a late night salivary cortisol the preferred diagnostic test for Cushing syndrome?
- CRH is released in cyclic pattern from hypothalamus, diurnal peaks in the morning and nadir in the evening of ACTH and cortisol levels
- Diurnal variation is lost in pts with Cushing syndrome, will have elevated levels of evening plasma cortisol
- Late-night salivary cortisol is effective and convenient screening for Cushings
27
Interpret the results of a late night salivary cortisol test for Cushings
Increased salivary cortisol levels – characteristic of Cushings
**Confirm results at least once
28
Identify the drug, dose, time of administration and timing of blood draw for an overnight low dose dexamethasone suppression test
- Dexamethasone, 1 mg (two 0.5 mg tablets), PO between 11 pm and midnight
- Single blood sample at 8 am the next morning for assay of serum cortisol and serum dexamethasone if available
29
Interpret the results of a growth hormone suppression and IGF-1 for a patient with acromegaly
- Normal pts have a nadir GH concentration <0.3 ng/mL after ingestion of 75 g glucose dose. Pts with acromegaly fail to show normal suppression
- Elevated IGF1/IGFBP3 support dx acromegaly or gigantism with appropriate signs
30
Interpret the results of a growth hormone suppression and IGF-1 for a patient with GH deficiency
- Normal pts have a peak GH concentration >5 ng/mL in children and >4 ng/mL in adults following stimulation. Low levels after stimulation indicate GH deficiency
- IGF1/IGFBP3 <2.5th percentile for age are consistent with GH deficiency or GH resistance
31
Interpret a serum prolactin level when used for diagnosis of medical therapy
- Serum prolactin concentrations generally parallel tumor size. Macroadenomas (>10 mm in diameter) are usually associated with concentrations >250 ng/mL
- Concentration >500 ng/mL is diagnostic of macroprolactinoma
32
Interpret a serum prolactin level when used for monitoring of medical therapy
- 60-80% of pts will reach a normal level (Males ≥ 18: 4.0 – 15/2 ng/mL, Females ≥ 18: 4.8 – 23.3 ng/mL)
- Pts who don’t show decrase in prolactin levels or tumor shrinkage might require additional therapeutic measures
33
8 meds that can cause an increased prolactin concentration
- Estrogens
- Dopamine receptor blockers (phenothiazines)
- Dopamine antagonists (metoclopramide, domperidone)
- Alpha-methyldopa
- Cimetidine
- Opiates
- Antihypertensive meds
- Other antidepressants and antipsychotics
34
What is normal testosterone range for men
Males ≥ 19 : 240 to 950 ng/dL
35
State the relationship between testosterone and hypogonadism
Decreased testosterone (below reference range) indicate partial or complete hypogonadism
36
Treatment goal of testosterone replacement
- Normalize serum testosterone and LH
- Trough levels of serum testosterone should be within the normal range
- Peak levels of serum testosterone should not be significantly above normal range
37
Expected findings of aldosterone and PRA in a person with primary aldosteronism
- High ratio of serum aldosterone (SA):plasma renin activity (PRA) is positive screening result, do further testing
- SA/PRA ratio of ≥ 20 is only interpretable with an SA ≥ 15 and indicates probably primary aldosteronism
38
State the effect of ACE inhibitor on a PRA
falsely elevate PRA
39
State the significance of an elevated DHEA-S level
- DHEA is the principal human C-19 steroid. Low androgenic potency but serves as major direct or indirect precursor for most sex steroids.
- Elevated levels indicate increased adrenal androgen production
- Pronounced elevations (>600 mcg/dL) may be indicative of androgen-producing adrenal tumors
40
Identify the best test to rule out a pheochromocytoma
- Metanephrines (fractionated, free plasma)
| - 24-hr urine metanephrines and catecholamines confirm positive metanephrine results
