Lab med - Pituitary and Adrenal glands Flashcards
Purpose of ACTH
determine cause of hypercortisolism and hypocortisolism
Purpose of serum cortisol
- discriminate between primary and secondary adrenal insufficiency
- differentiate diagnosis of Cushing syndrome
Purpose of 24 hour free cortisol/cortisone
- 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
Purpose of late night salivary cortisol
- Screening test for Cushing syndrome (hypercortisolism)
- Dx of Cushing syndrome in pts presenting with sx or signs suggestive of the disease
Purpose of overnight low dose dexamethasone suppression test (LDST)
Quick screening for nonsuppressible cortisol production and subclinical or clinical Cushing’s syndrome
Purpose of growth hormone
- Dx of acromegaly, assessment of treatment efficacy
- Dx of human growth hormone deficiency (done in conjunction with GH stimulation test)
Purpose of IGF-1
- 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
Purpose of plasma aldosterone
- 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)
Purpose of renin activity
- 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
Purpose of prolactin
- Aid in eval of pituitary tumors, amenorrhea, galactorrhea, infertility, hypogonadism
- Monitor therapy of prolactin-producing tumors
Purpose of testosterone (8)
- 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
Purpose of serum DHEAS
- 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
Purpose of metanephrines (fractionated, free, plasma)
Screening test for presumptive dx of catecholamine-secreting pheochromocytomas or paragangliomas
Purpose of 24-hour urine metanephrines and catecholamines
- First and second order screening test for presumptive dx of catecholamine-secreting pheochromocytomas and paragangliomas
- Confirms positive plasma metanephrine results
What disorders are associated with hypercortisolism
- 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)
What disorders are associated with hypocortisolism
- Addison disease – primary adrenal insufficiency
- Secondary adrenal insufficiency
- Pituitary insufficiency
- Hypothalamic insufficiency
- Congenital adrenal hyperplasia – defects in enzyme involved in cortisol synthesis
How to interpret elevated ACTH in patient with hypocortisolism
indicates primary adrenal insufficiency
How to interpret suppressed ACTH level in pt with hypercortisolism (Cushing)
Consistent with cortisol-producing adrenal adenoma or carcinoma, primary adrenal micronodular hyperplasia, or exogenous corticosteroid use
What interferes with ACTH assay?
glucocorticoids
What should pt not take before an ACTH lab test?
biotin
What are the expected ACTH and cortisol levels in a pt with primary adrenal insufficiency?
- ACTH levels are increased
- cortisol is decreased
What are the expected ACTH and cortisol levels in a pt with secondary adrenal insufficiency?
Both ACTH and cortisol are decreased
Identify the expected results of a 24-hour urinary excretion of cortisol in a person with Cushing syndrome
Increased 24 hour urinary excretion of cortisol or cortisone
Identify the factors that affect a 24-hour urinary excretion of cortisol (5)
- 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
what is the preferred screening test for Cushing syndrome
24-hour UFC excretion
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
Interpret the results of a late night salivary cortisol test for Cushings
Increased salivary cortisol levels – characteristic of Cushings
**Confirm results at least once
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
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
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
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
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
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
What is normal testosterone range for men
Males ≥ 19 : 240 to 950 ng/dL
State the relationship between testosterone and hypogonadism
Decreased testosterone (below reference range) indicate partial or complete hypogonadism
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
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
State the effect of ACE inhibitor on a PRA
falsely elevate PRA
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
Identify the best test to rule out a pheochromocytoma
- Metanephrines (fractionated, free plasma)
- 24-hr urine metanephrines and catecholamines confirm positive metanephrine results
