375 Thyroid Gland Physiology and Testing

Question 1

Normal weight of thyroid gland (H20 C375 P2692)

Answer 1

12-20 g

Question 2

The thyroid gland develops from the floor of the primitive pharynx during what week of gestation? (H20 C375 P2692)

Answer 2

3rd week

Question 3

Thyroid hormon synthesis begins at about how many weeks’ gestation?

Answer 3

11 weeks

Question 4

Protein precursor of thyroid hormones (H20 C375 P2692)

Answer 4

Thyroglobulin

Question 5

The most useful physiologic marker of thyroid hormone action (H20 C375 P2692)

Answer 5

TSH

Question 6

The major positive regulator of TSH synthesis (H20 C375 P2693)

Answer 6

TRH

Question 7

Dominant regulator of TSH production (H20 C375 P2693)

Answer 7

Thyroid hormones

Question 8

Peak TSH secretion occurs how many minutes after exogenous TRH? (H20 C375 P2693)

Answer 8

15 minutes

Question 9

Plasma half-life of TSH

Answer 9

50 mins

Question 10

Critical first step in thyroid hormone synthesis (H20 C375 P2693)

Answer 10

Iodide uptake

Question 11

A disorder characterized by defective organification of iodine, goiter, and sensorineural deafness, caused by a mutation of the pendrin gene (H20 C375 P2693)

Answer 11

Pendred syndrome

Question 12

Most common cause of preventable mental deficiency (H20 C375 P2693)

Answer 12

Iodine deficiency

Question 13

RDA for iodine for pregnant women (H20 C375 P2694)

Answer 13

220 μg

Question 14

Urinary iodine in iodine-sufficient populations (H20 C375 P2694)

Answer 14

> 10 μg/dL

Question 15

Uncoupled mono- and diiodoty- rosines (MIT, DIT) are deiodinated by this enzyme (H20 C375 P2694)

Answer 15

Dehalogenase

Question 16

A phenomenon where excess iodide transiently inhibits thyroid iodide organification (H20 C375 P2694)

Answer 16

Wolff-Chaikoff effect

Question 17

Women with a precarious iodine intake of this amount are most at risk of developing a goiter during pregnancy or giving birth to an infant with a goiter and hypothyroidism. (H20 C375 P2694)

Answer 17

<50 μg/d

Question 18

The World Health Organization recommends a daily iodine intake of this amount during pregnancy and lactation (H20 C375 P2694)

Answer 18

250 μg

Question 19

RDA for iodine for breastfeeding women (H20 C375 P2694)

Answer 19

290 μg

Question 20

Prenatal vitamins should contain this amount of iodine per tablet. (H20 C375 P2694)

Answer 20

150 μg

Question 21

hCG- induced changes in thyroid function can result in this condition, that may be associated with hyperemesis gravidarum. (H20 C375 P2694)

Answer 21

Transient gestational hyperthyroidism

Question 22

Total T4 and T3 levels are about how many times higher throughout pregnancy (H20 C375 P2694)

Answer 22

1.5×

Question 23

Serum half-life of T4 (H20 C375 P2695)

Answer 23

7 days

Question 24

Thyroid hormone requirements are increased by up to ___ during pregnancy in levothyroxine-treated hypothyroid women. (H20 C375 P2695)

Answer 24

45%

Question 25

Protein that carries about 80% of bound thyroid hormones (H20 C375 P2695)

Answer 25

TBG

Question 26

Most important source of reveres T3 (H20 C375 P2696)

Answer 26

Type III deiodinase

Question 27

An autosomal dominant disorder characterized by elevated thyroid hormone levels and inappropriately normal or elevated TSH. (H20 C375 P2696)

Answer 27

Resistance to thyroid hormone (RTH)

Question 28

Provides definitive diagnosis of RTH (H20 C375 P2696)

Answer 28

DNA sequence analysis of the TRβ gene

Question 29

Provides the most accurate measurement of thyroid volume and nodularity and is useful for assessment of goiter prevalence in iodine deficient regions.

Answer 29

Ultrasound imaging

Question 30

Sign characterized by difficulty breathing especially when the arms are raised. (H20 C375 P2697)

Answer 30

Pemberton’s sign

Question 31

It is reasonable to only measure antibodies to this protein when considering autoimmune thyroid disease (H20 C375 P2697)

Answer 31

TPO antibodies

Question 32

Serum Tg levels are increased in all type of thyrotoxicosis except: (H20 C375 P2697)

Answer 32

Thyrotoxicosis factitia