Quiz 3

Question 1

The most metabolically active thyroid hormone is:
Select one:
a. Monoiodothyronine
b. Diiodothyronine
c. Triiodothyronine
d. Tetraiodothyronine
e. Reverse Triiodothyronine

Answer 1

Triiodothyronine

Question 2

Inhibitors of thyroid hormone secretion, function, and metabolism include all of the following except:
Select one:
a. Estrogen
b. Growth hormone 
c. Dopamine
d. Cortisol
e. Somatostatin

Answer 2

Growth hormone (Yes…thyroid hormone exerts a permissive effect upon the anabolic and metabolic effects of GH, and increases pituitary synthesis of GH. GH increases peripheral conversion of T4 –> T3.)

Question 3

Which statement is not true regarding thyroid parafollicular cells?
Select one:
a. Secrete a peptide hormone involved in inhibiting bone resorption
b. Are the cell type found proliferating in medullary thyroid cancers
c. Contain Na/I symporters
d. Found in the spaces between thyroid follicles
e. None of the above

Answer 3

Contain Na/I symporters (Correct–these are found only on thyroid follicular cells; these cells concentrate iodine)

Question 4

Thyroglossal duct cysts are nearly always malignant:
Select one:
True
False

Answer 4

False (but they may be hyper-secreting thyroid hormone)

Question 5

According to the WHO, the daily required intake of iodine for adult men & non-pregnant women is:
Select one:
a. 50 mcg
b. 150 mcg
c. 400 mcg
d. 1000 mcg
e. None of the above

Answer 5

150 mcg(Correct…and the typically upper limit is set at 300 mcg/day. Pregnant and lactating women generally need between 250-300 mcg/day to ensure proper thyroid hormone synthesis.)

Question 6

The follicular hyperkeratosis often seen in patients with untreated hypothyroidism is directly related to decreased serum levels of which of the following?
Select one:
a. Vitamin A 
b. Vitamin B3
c. Vitamin C
d. 25(OH)VitaminD3
e. All of the above

Answer 6

Vitamin A (Correct…this is often related to poor conversion of beta-carotene into vitamin A due to low thyroid levels)

Question 7

The enzyme found within thyroid follicles that oxidizes iodine ions to molecular iodide is:
Select one:
a. Thyroglobulin
b. Thyroxine
c. Triiodothyronine
d. Thyroperoxidase
e. Deiodinase

Answer 7

Thyroperoxidase

Question 8

The sodium/iodide symporter (NIS) is a transmembrane protein located primarily in:
Select one:
a. Thyroid parafollicular cells
b. Thyroid follicular cells
c. Thyroid colloid
d. Parathyroid cells
e. Thyroid arterioles

Answer 8

Thyroid follicular cells

Question 9

TSH has all of the following actions, except:
Select one:
a. Causes hypertrophy & hyperplasia of the thyroid follicular cells
b. Decreases vascularity of the thyroid gland
c. Upregulates the sodium/iodide symptorter
d. Stimulates iodination of thyroglobulin
e. Increases endocytosis of iodinated thyroglobulin within follicular cells

Answer 9

Decreases vascularity of the thyroid gland(Correct–it increases vascularity of the gland)

Question 10

Which nerve passes through the thyroid gland and may be damaged in patients undergoing surgical resection of the thyroid?
Select one:
a. Phrenic nerve
b. Left Vagus nerve
c. Right Vagus nerve
d. Recurrent Laryngeal nerve
e. Hypoglossal nerve

Answer 10

Recurrent Laryngeal nerve

Question 11

Which statement is not true regarding deiodinaess?
Select one:
a. All 3 types of deiodiases convert T4 to T3
b. Require selenium as a cofactor
c. Type 3 deiodinase is upregulated by cortisol
d. Cold exposure, overfeeding, and increased catecholamines will increase activity of type 2 deiodinase
e. Propylthiouracil (PTU) inhibits type 1 deiodinase more strongly than type 2 and type 3 deiodinases

Answer 11

All 3 types of deiodiases convert T4 to T3

Question 12

Type 3 deiodinase (D3) primarily metabolizes T4 and T3 to:
Select one:
a. T1 (MIT)
b. T2 (DIT)
c. Reverse T3 (rT3)
d. Calcitonin
e. None of the above

Answer 12

Reverse T3 (rT3)

Question 13

Iodine-131, a radioactive isotope of iodine used in the treatment of certain forms of hyperthyroidism, has a half-life of:
Select one:
a. 1 day
b. 8 days
c. 2 weeks
d. 1 month
e. 1 year

Answer 13

8 days

Question 14

Absence of thyroid hormones (T4 and T3) during fetal life, resulting in a poorly developed nervous system & a form of mental retardation, is known as:
Select one:
a. Gigantism
b. Acromegaly
c. Laron dwarfism
d. Cretinism
e. Turner syndrome

Answer 14

Cretinism

Question 15

Actions of thyroid hormone (T3) include all of the following except:
Select one:
a. Increases heart rate and cardiac output
b. Increases bone turnover
c. Slows intestinal peristalsis
d. Increases cholesterol clearance via LDL-receptors in the liver
e. Increases speed of skeletal muscle contractions

Answer 15

Slows intestinal peristalsis