Endocrine Function III Part 3

Question 0

Overnight Dexamethasone Suppression Test (screening test)

-Principle

Answer 0

Feedback mechanism of hypersecretion can be tested by administering a potent glucocorticoid and judging suppression of ACTH secretion by measuring serum or urine cortisol levels

Question 1

What is the clinical use of the corticotropin releasing hormone (CRH) test?

Answer 1

Differentiates secondary (pituitary) and tertiary (hypothalamic) adrenal sufficiency

Question 2

Overnight Dexamethasone Suppression Test (screening test)

-Diagnostic Use

Answer 2

Differentiate normal patient from Cushing’s syndrome, either due to Cushing’s disease, adrenal tumor, or ectopic ACTH syndrome

Question 3

Overnight Dexamethasone Suppression Test (screening test)

-expected normal response

Answer 3

decreased cortisol (<3 ug/dL)

Question 4

Overnight Dexamethasone Suppression Test (screening test)

-cause of abnormal results

Answer 4

increased cortisol (>10 ug/dL) = Cushing’s Syndrome

Question 5

Which causes of Cushing’s syndrome may be differentiated using the high-dose test?

Answer 5

adrenal tumors, nonendocrine ACTH-secreting tumors, and pituitary Cushing’s disease

Question 6

What do normal results look like in high dose dexamethasone suppression test look like?

Answer 6

50% suppression of cortisol production

Question 7

How do abnormal results differ in Cushing’s and adrenal/ectopic tumors during the high dose test?

Answer 7

Cushing’s = most suppress cortisol production

Adrenal/ectopic tumors = no change in cortisol levels

Question 8

Name the three principle hormones classified as catecholamines and their sites of synthesis.

Answer 8

1 epinephrine (80-90% medulla production)
2 norepinephrine (10-20% medulla production)
3 dopamine (small amount produced in adrenal medulla)

Question 9

These catecholamines have a marked influence on the vascular system.

Answer 9

dopamine and norepinephrine

Question 10

This catacholamine influences metabolic processes, especially carbohydrate metabolism.

Answer 10

epinephrine

Question 11

This catecholamine inhibits phenylethanolamine-N-methyltransferase

Answer 11

epinephrine

Question 12

This catecholamine inhibits tyrosine hydroxylase.

Answer 12

Norepinephrine

Question 13

What is the cause of pheochromocytomas?

Answer 13

tumor in adrenal medulla, too much catecholamines

Question 14

What is the principle clinical symptom of pheochromocytomas?

Answer 14

hypertension

Question 15

What is the best specific urine screening test for pheochromocytomas?

Answer 15

urinary metanephrines

Question 16

What is the best diagnostic test for pheochromocytomas?

Answer 16

urinary VMA

Question 17

What is the commonly affected age group of neuroblastomas?

Answer 17

pediatric

Question 18

What are the clinical symptoms for neuroblastomas?

Answer 18

tumor in or near adrenal gland producing a lot of dopamine, causing transient hypertension and tachycardia

Question 19

What is the best specific urine screening test for neuroblastomas?

Answer 19

urinary homovanillic acid (HVA) (diagnostic)