Deck 26: Catecholamines and Serotonin

Question 1

Regarding catecholamines,the amino acid from which dopamine is synthesized?

A) Threonine
B) Tryptophan
C) Tyrosine
D) Cytosine

Answer 1

Tyrosine

Question 2

A man visits his physician complaining of hypertension (elevated heart rate and blood pressure),periodic bouts of profuse sweating,and occasional severe headaches.These symptoms are indicative of:

A) Cushing syndrome.
B) carcinoid syndrome.
C) pheochromocytoma.
D) neuroblastoma.

Answer 2

pheochromocytoma.

Question 3

In the diagnosis of pheochromocytoma,what hormone is being assessed by measuring urine metanephrine?

A) Epinephrine
B) Dopamine
C) Serotonin
D) Norepinephrine

Answer 3

Epinephrine

Question 4

In the gastrointestinal (GI)tract,dopamine functions as a modulator of the enteric nervous system or as a paracrine substance.What essential enzyme is required for synthesis of dopamine in the dopaminergic system in the GI tract?

A) Tryptophan hydroxylase
B) Tyrosine hydroxylase
C) Catechol-O-methyltransferase (COMT)
D) Monoamine oxidase (MAO)

Question 5

Currently,the most common method of analysis for plasma catecholamines is:

A) liquid chromatography (LC)with electrochemical (EC)detection.
B) HPLC.
C) mass spectrometry.
D) spectrophotometry.

Question 6

Metabolism of norepinephrine and epinephrine in adrenal chromaffin cells requires the presence of which one of the following enzymes for conversion into normetanephrine and metanephrine?

A) Catechol-O-methyltransferase
B) Dopamine- $\beta$ -hydroxylase
C) Tyrosine hydroxylase
D) Monoamine oxidase

Question 7

The urinary metabolite measured as an indicator of dopamine synthesis is:

A) metanephrine.
B) homovanillic acid.
C) vanillylmandelic acid.
D) catechol-O-methyltransferase.

Question 8

Measurement of urinary metanephrine and vanillylmandelic acid (VMA)assesses the amount of hormone secreted by the _____ and is done to detect the presence of _____.

A) gastrointestinal (GI)tract; carcinoid tumor
B) adrenal medulla; pheochromocytoma
C) adrenal cortex; Cushing syndrome
D) medulla of the brain; neuroblastoma

Question 9

MATCHING
Match the disorder with the diagnostic analyte measured in the laboratory.
Plasma/urine metanephrines

A)Gastroenteropancreatic endocrine tumor
B)Tumor of adrenal medullary chromaffin cells
C)Pineal gland tumor
D)Neuroblastoma

Question 10

In the assessment of equivocal results in pheochromocytoma testing,the clonidine suppression test is used to differentiate between:

A) elevated blood pressure caused by pheochromocytoma versus that caused by carcinoid tumor.
B) increased serotonin production by the GI tract versus serotonin from the brain.
C) adrenal gland and GI tract increased synthesis of dopamine.
D) adrenal gland and sympathetic nervous system increases in catecholamine synthesis.

Question 11

Dopamine in the central nervous system functions as a neurotransmitter important for regulating an overall state of attention and vigilance.

Question 12

Which one of the following substances is measured in urine to determine the presence of a gastroenteropancreatic neuroendocrine tumor in an individual with carcinoid syndrome?

A) VMA
B) Metanephrine
C) Homovanillic acid (HVA)
D) 5-Hydroxyindole acetic acid (5-HIAA)

Question 13

All of the following represent metabolic effects caused by the action of epinephrine secreted from the adrenal gland except:

A) increased lipolysis.
B) bronchodilation.
C) increased protein synthesis.
D) glycogenolysis.

Question 14

The rate-limiting step in the biosynthesis of catecholamines is the:

A) conversion of 3-methoxy-4-hydroxyphenylglycol (MHPG)to VMA by alcohol dehydrogenase.
B) conversion of tryptophan to 5-hydroxytryptophan by tryptophan hydroxylase.
C) metabolism by catechol-O-methyltransferase (COMT)to MHPG.
D) conversion of tyrosine to 3,4-dihydroxyphenylalanine by tyrosine hydroxylase.

Question 15

In the sympathetic component of the autonomic nervous system,norepinephrine acts to:

A) increase heart rate and blood pressure.
B) induce hypotension.
C) dilate the peripheral blood vessels.
D) increase the release of serotonin from the brain.

Question 16

A neoplasm considered to be a pediatric cancer that is derived from the neural crest cells of the sympathetic nervous system is referred to as a:

A) pheochromocytoma.
B) gastroenteropancreatic neuroendocrine tumor.
C) neuroblastoma.
D) carcinoid tumor.

Question 17

An overnight fast is recommended for individuals being tested for carcinoid syndrome because:

A) dietary interference,particularly with foods that contain 5-hydroxyindoles,will produce a false increase in plasma 5-HIAA measurement.
B) no food should be present in the GI tract for 12 hours before analysis of catecholamine metabolites.
C) monoamine systems are targets of certain components of foods that contain tyrosine,and a false-negative result will occur in HVA testing.
D) certain foods interfere with the methods of analysis used for serotonin analysis,particularly the high performance liquid chromatography (HPLC)assays.

Question 18

The use of tricycle antidepressants by an individual may produce incorrect results in the measurement of norepinephrine and normetanephrine during testing for pheochromocytoma.How will results be affected and why?

A) The results will be falsely elevated because of inhibition of monoamine reuptake.
B) The results will be falsely decreased because of increased synthesis of monoamine oxidase.
C) The results will be falsely elevated because these drugs increase synthesis of dopamine.
D) The results will be falsely decreased because these drugs inhibit tyrosine hydroxylase.

Question 19

Pheochromocytomas:

A) produce hypotension (decreased blood pressure).
B) tend to secrete serotonin in increased amounts.
C) are benign in the majority of cases.
D) are tumors derived from enterochromaffin cells.

Question 20

The amino acid precursor for the neurotransmitter serotonin (5HT)is:

A) tyrosine.
B) tryptophan.
C) threonine.
D) cytosine.

Question 21

MATCHING
Match the disorder with the diagnostic analyte measured in the laboratory.
Urinary VMA

A)Gastroenteropancreatic endocrine tumor
B)Tumor of adrenal medullary chromaffin cells
C)Pineal gland tumor
D)Neuroblastoma

Question 22

MATCHING
Match the disorder with the diagnostic analyte measured in the laboratory.
Melatonin

A)Gastroenteropancreatic endocrine tumor
B)Tumor of adrenal medullary chromaffin cells
C)Pineal gland tumor
D)Neuroblastoma

Question 23

MATCHING
Match the disorder with the diagnostic analyte measured in the laboratory.
Urinary 5-HIAA

A)Gastroenteropancreatic endocrine tumor
B)Tumor of adrenal medullary chromaffin cells
C)Pineal gland tumor
D)Neuroblastoma