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Endocrine 2 > Lab med - Pituitary and Adrenal glands > Flashcards

Lab med - Pituitary and Adrenal glands Flashcards

1
Q

Purpose of ACTH

A

determine cause of hypercortisolism and hypocortisolism

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2
Q

Purpose of serum cortisol

A
  • discriminate between primary and secondary adrenal insufficiency
  • differentiate diagnosis of Cushing syndrome
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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
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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

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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

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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)

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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
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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)
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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
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10
Q

Purpose of prolactin

A
  • Aid in eval of pituitary tumors, amenorrhea, galactorrhea, infertility, hypogonadism
  • Monitor therapy of prolactin-producing tumors
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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
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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
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13
Q

Purpose of metanephrines (fractionated, free, plasma)

A

Screening test for presumptive dx of catecholamine-secreting pheochromocytomas or paragangliomas

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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
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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)
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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
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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
Q

what is the preferred screening test for Cushing syndrome

A

24-hour UFC excretion

26
Q

Why is a late night salivary cortisol the preferred diagnostic test for Cushing syndrome?

A
  • 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
Q

Interpret the results of a late night salivary cortisol test for Cushings

A

Increased salivary cortisol levels – characteristic of Cushings
**Confirm results at least once

28
Q

Identify the drug, dose, time of administration and timing of blood draw for an overnight low dose dexamethasone suppression test

A
  • 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
Q

Interpret the results of a growth hormone suppression and IGF-1 for a patient with acromegaly

A
  • 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
Q

Interpret the results of a growth hormone suppression and IGF-1 for a patient with GH deficiency

A
  • 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
Q

Interpret a serum prolactin level when used for diagnosis of medical therapy

A
  • 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
Q

Interpret a serum prolactin level when used for monitoring of medical therapy

A
  • 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
Q

8 meds that can cause an increased prolactin concentration

A
  • Estrogens
  • Dopamine receptor blockers (phenothiazines)
  • Dopamine antagonists (metoclopramide, domperidone)
  • Alpha-methyldopa
  • Cimetidine
  • Opiates
  • Antihypertensive meds
  • Other antidepressants and antipsychotics
34
Q

What is normal testosterone range for men

A

Males ≥ 19 : 240 to 950 ng/dL

35
Q

State the relationship between testosterone and hypogonadism

A

Decreased testosterone (below reference range) indicate partial or complete hypogonadism

36
Q

Treatment goal of testosterone replacement

A
  • 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
Q

Expected findings of aldosterone and PRA in a person with primary aldosteronism

A
  • 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
Q

State the effect of ACE inhibitor on a PRA

A

falsely elevate PRA

39
Q

State the significance of an elevated DHEA-S level

A
  • 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
Q

Identify the best test to rule out a pheochromocytoma

A
  • Metanephrines (fractionated, free plasma)

- 24-hr urine metanephrines and catecholamines confirm positive metanephrine results

Endocrine 2 (15 decks)

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