Thyroid Hormone

Question 1

Thiocyanate and perchlorate are (competitive/ noncompetitive) __________ inhibitors of Na+-I-
cotransport.

Answer 1

Competetive

Question 2

The thyroid gland secretes 90% of its thyroid hormone in the form of (triiodothyronine/tetraiodothyronine) ____________.

Answer 2

Tetraiodothyronine

Question 3

The material in the center of a thyroid follicle surrounded by follicular epithelial cells is called _________

Answer 3

Colloid

Question 4

Thyroglobulin contains a large amount of (amino acid) ___________

Answer 4

Tyrosine

Question 5

Iodine ions are oxidized to I2 by (enzyme)____________ when they reach the apical membrane of the cell.

Answer 5

thyroid peroxidase

Question 6

The formation of (triiodothyronine/tetraiodothyronine) is much faster than the other.

Answer 6

tetraiodothyronine

Question 7

The form of thyroid hormone that is more active is (triiodothyronine/tetraiodothyronine) ____________

Answer 7

T3

Question 8

____________ is formed by the combination of one monoiodotyrosine and one diiodotyrosine molecule.

Answer 8

T3

Question 9

The T3 resin uptake test assesses the circulating levels of ____________

Answer 9

Thyroxine Binding globulin

Question 10

The hepatic breakdown of thyroxine-binding globulin is inhibited during pregnancy due to high levels of __________ causing an increased synthesis of
thyroid hormones by removing negative feedback

Answer 10

estrogen

Question 11

The Na+-I- cotransport pump increases activity when the body has too (much/little) ________ iodine

Answer 11

little iodine

Question 12

Tetraiodothyronine is formed by the combination of two __________ molecules

Answer 12

Di-iodotyrosine

Question 13

Thyroid gland growth is regulated by __________.

Answer 13

Thyroid Stimulatin hormone

Question 14

The thyroid gland synthesizes thyroid hormone in its _________ epithelial cells

Answer 14

Follicular

Question 15

Tetraiodothyronine is converted to triiodothyronine by the enzyme ____________ by removing one atom from I2.

Answer 15

5’- deiodinase

Question 16

The ________ effect occurs when large amounts I- inhibit organification, which is the combination of I2 and
tyrosine of thyroglobulin to form monoiodotyrosine and
diiodotyrosine.

Answer 16

Wolff-Chaikoff

Question 17

The __________transports iodine from blood into follicular epithelial cells.

Answer 17

Na+/I- symporter

Question 18

Decreased thyroxine-binding globulin, such as in hepatic failure, results in (increased/decreased) _________ levels of free thyroid hormones and decreased synthesis of thyroid hormones.

Answer 18

Increased

Question 19

A dietary I- deficiency appears similar to a deficiency of (enzyme) ____________

Answer 19

thyroid deiodinase

Question 20

Heart rate and contractility increase when thyroid hormone is released due to its effect on their ___________ receptors.

Answer 20

beta-1 -adrenergic