Exam 5: Lecture 67: Throid Hormones 1: AI Questions

Question 1

What is the primary component required for thyroid hormone synthesis?
A) Iodine
B) Calcium
C) Iron
D) Magnesium

Answer 1

A

Question 2

Which thyroid hormone is the most biologically active?
A) Triiodothyronine (T3)
B) Reverse T3 (rT3)
C) Thyroxine (T4)
D) Thyroglobulin

Answer 2

A

Question 3

The Wolff-Chaikoff effect is best described as:
A) A temporary suppression of thyroid hormone synthesis due to high iodide intake
B) A chronic increase in thyroid hormone production
C) Increased TSH sensitivity
D) The conversion of T4 to rT3

Answer 3

A

Question 4

The main active form of thyroid hormone in target tissues is:
A) T4
B) rT3
C) T3
D) Thyroglobulin

Answer 4

C

Question 5

Which enzyme is responsible for converting T4 to T3 in peripheral tissues?
A) Pendrin
B) Deiodinase
C) Thyroid peroxidase
D) Na+/I- symporter

Answer 5

B

Question 6

During thyroid hormone synthesis, iodide is transported into the follicular cell via:
A) Na+/K+ ATPase
B) Chloride channel
C) Na+/I- symporter
D) Pendrin

Answer 6

C

Question 7

The Wolff-Chaikoff effect refers to:
A) Increased TSH secretion in response to low T3 levels
B) Temporary inhibition of thyroid hormone synthesis due to high iodide levels
C) Enhanced T4 secretion during stress
D) Decreased TBG binding capacity in liver disease

Answer 7

B

Question 8

The primary protein that binds circulating T4 is:
A) Albumin
B) Thyroxine-binding globulin (TBG)
C) Transthyretin
D) Corticosteroid-binding globulin

Answer 8

B

Question 9

Which hormone is released from the hypothalamus to stimulate TSH secretion?
A) Corticotropin-releasing hormone (CRH)
B) Growth hormone-releasing hormone (GHRH)
C) Thyrotropin-releasing hormone (TRH)
D) Dopamine

Answer 9

C

Question 10

Which of the following increases the conversion of T4 to rT3?
A) Fasting
B) High carbohydrate intake
C) Exercise
D) Pregnancy

Answer 10

A

Question 11

The majority of thyroid hormone stored in the thyroid gland is in the form of:
A) Free T3
B) Free T4
C) Thyroglobulin-bound T4 and T3
D) Calcitonin

Answer 11

C

Question 12

Which thyroid hormone has the longest half-life in circulation?
A) T3
B) T4
C) rT3
D) Calcitonin

Answer 12

B

Question 13

Which of the following best describes the effect of TSH on the thyroid gland?
A) Decreases thyroglobulin synthesis
B) Stimulates iodide uptake and thyroid hormone synthesis
C) Inhibits release of T3 and T4
D) Increases deiodinase activity

Answer 13

B

Question 14

Parafollicular cells of the thyroid gland produce:
A) T4
B) T3
C) Calcitonin
D) rT3

Answer 14

C

Question 15

In a patient with hyperthyroidism, you would expect:
A) Elevated TSH and low T4
B) Low TSH and high T4
C) High rT3 and normal T4
D) Elevated TRH and decreased T3

Answer 15

B

Question 16

The primary effect of T3 on target tissues is to:
A) Decrease heart rate
B) Lower basal metabolic rate
C) Increase protein synthesis and oxygen consumption
D) Decrease glucose absorption

Answer 16

C

Question 17

The role of deiodinase type 2 is to:
A) Convert T4 to rT3
B) Inactivate T3
C) Convert T4 to T3 in peripheral tissues
D) Oxidize iodide in the follicle

Answer 17

C

Question 18

n hepatic failure, levels of circulating thyroid hormone are decreased because:
A) TSH secretion is increased
B) Deiodinase activity is enhanced
C) Thyroid-binding proteins are reduced
D) TRH release is elevated

Answer 18

C

Question 19

The escape phenomenon in the context of the Wolff-Chaikoff effect refers to:
A) Permanent suppression of thyroid hormone synthesis
B) Restoration of normal thyroid function after initial iodide-induced inhibition
C) Increased TSH levels after high iodide intake
D) Decreased conversion of T4 to T3

Answer 19

B

Question 20

T3 has a shorter half-life than T4 because:
A) It is less protein-bound in circulation
B) It is produced in smaller amounts
C) It has a lower molecular weight
D) It is stored in the thyroid gland for shorter periods

Answer 20

A

Question 21

Which of the following conditions would most likely increase circulating rT3 levels?
A) Hyperthyroidism
B) Chronic illness
C) Increased TSH secretion
D) Iodine deficiency

Answer 21

B

Question 22

Which hormone provides negative feedback to the anterior pituitary to decrease TSH release?
A) T4
B) Calcitonin
C) Insulin
D) TBG

Answer 22

A

Question 23

Thyroid peroxidase deficiency would result in:
A) Increased synthesis of T3 and T4
B) Inability to iodinate tyrosine residues
C) Enhanced release of TSH
D) Elevated circulating calcitonin levels

Answer 23

B

Question 24

In sick euthyroid syndrome, the typical thyroid hormone profile is:
A) Normal TSH, low T3, high rT3
B) Elevated TSH, elevated T4, normal rT3
C) Decreased T4, increased T3, low TBG
D) High T3, high TSH, low T4

Answer 24

A

Question 25

A dietary deficiency in iodine would most likely result in:
A) Hyperthyroidism
B) Increased T4 production
C) Goiter formation
D) Increased calcitonin secretion

Answer 25

C

Question 26

Which hormone directly stimulates iodide uptake by thyroid cells?
A) TRH
B) TSH
C) GH
D) ADH

Answer 26

B

Question 27

The primary regulator of thyroid hormone synthesis is:
A) Serum calcium levels
B) Plasma iodide concentration
C) Hypothalamic TRH release
D) Parathyroid hormone

Answer 27

C

Question 28

The primary site of conversion of T4 to T3 in the body is:
A) Thyroid gland
B) Kidney
C) Liver
D) Bone

Answer 28

C

Question 29

Which of the following would most likely increase circulating levels of free T3?
A) Increased binding to thyroxine-binding globulin (TBG)
B) Decreased deiodinase activity
C) Decreased liver protein synthesis
D) High carbohydrate diet

Answer 29

C

Question 30

A dog with chronic renal disease is likely to have altered thyroid hormone levels due to:
A) Increased TBG production
B) Enhanced clearance of thyroid hormones
C) Decreased circulating TSH
D) Increased production of T4

Answer 30

B

Question 31

Which of the following best describes the action of T3 on target tissues?
A) Decreases metabolic rate and oxygen consumption
B) Stimulates protein breakdown and decreases glucose uptake
C) Increases protein synthesis, glucose absorption, and lipid breakdown
D) Inhibits insulin secretion from the pancreas

Answer 31

C

Question 32

In a patient with iodine deficiency, the most likely thyroid hormone profile would be:
A) High T4, high T3, low TSH
B) Low T4, low T3, high TSH
C) High rT3, low T4, low TSH
D) Normal T4, high T3, low rT3

Answer 32

B

Question 33

In hyperthyroidism, increased levels of T3 and T4 have what effect on the cardiovascular system?
A) Bradycardia and decreased cardiac output
B) Increased heart rate and cardiac output
C) No effect on heart rate but increased peripheral resistance
D) Decreased blood pressure and bradycardia

Answer 33

B

Question 34

The main reason why T4 is considered a prohormone is because:
A) It is the most active thyroid hormone
B) It is converted to the biologically active T3 in target tissues
C) It has a higher affinity for nuclear receptors than T3
D) It binds directly to membrane receptors

Answer 34

B

Question 35

Which of the following is a common clinical sign of hypothyroidism in dogs?
A) Increased appetite and hyperactivity
B) Lethargy and weight gain
C) Diarrhea and vomiting
D) Increased heart rate and fever

Answer 35

B

Question 36

Which hormone stimulates the synthesis of thyroglobulin in the thyroid gland?
A) TSH
B) Calcitonin
C) Parathyroid hormone
D) Glucagon

Answer 36

A

Question 37

Chronic exposure to high TSH levels would most likely result in:
A) Atrophy of the thyroid gland
B) Hyperplasia and hypertrophy of follicular cells
C) Increased rT3 production
D) Decreased colloid storage in the thyroid gland

Answer 37

B

Question 38

The primary effect of T3 on mitochondria is:
A) Inhibition of ATP synthesis
B) Stimulation of heat production and increased oxygen consumption
C) Reduction of metabolic rate
D) Decreased mitochondrial biogenesis

Answer 38

B