[MCQ] Disorders of the Thyroid Gland- Part 2

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Disorders of the Thyroid Gland- Part 2

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Question 1

In iodine-sufficient populations, urinary iodine is level is ?

A	> 2 μg/dL
B	> 5 μg/dL
C	> 8 μg/dL
D	> 10 μg/dL

Question 1 Explanation:

Urinary iodine is >10 μg/dL in iodine-sufficient populations.

Question 2

Thyroglobulin releases T4 & T3 in which structure of thyroid cell ?

A	Mitochondria
B	Golgi apparatus
C	Lysosome
D	All of the above

Question 2 Explanation:

After coupling, Tg is taken back into thyroid cell, where it is processed in “lysosomes” to release T4 & T3.

Question 3

Which of the following is false about thyroglobulin (Tg) ?

A	660 kDa size
B	Dimeric protein
C	Consists of 2769 amino acids
D	None of the above

Question 3 Explanation:

thyroglobulin (Tg) is a large (660 kDa) dimeric protein that consists of 2769 amino acids.

Question 4

Congenital hypothyroidism is mostly due to mutations in ?

A	TPO
B	NIS
C	Dehalogenase
D	Pendrin

Question 4 Explanation:

Majority of congenital hypothyroidism are due to recessive mutations in TPO or Tg. Defects have also been identified in TSH-R, NIS, pendrin, hydrogen peroxide generation, and dehalogenase.

Question 5

Factors that influence thryoid hormone synthesis & release include all except ?

A	Insulin-like growth factor I (IGF-I)
B	Prolactin
C	Epidermal growth factor
D	Transforming growth factor  (TGF-)

Question 5 Explanation:

TSH is the dominant hormonal regulator of thyroid gland growth & function, but growth factors produced locally in thyroid gland also influence thyroid hormone synthesis which include insulin-like growth factor I (IGF-I), epidermal growth factor, transforming growth factor (TGF-) & endothelins.

Question 6

Wolff-Chaikoff effect is related to ?

A	Iodine deficiency
B	Excess iodide
C	Developmental abnormality of thyroid
D	All of the above

Question 6 Explanation:

Excess iodide transiently inhibits thyroid iodide organification, a phenomenon known as the Wolff- Chaikoff effect. Normal thyroid gland escapes from this inhibitory effect & iodide organification resumes. In patients with underlying autoimmune thyroid disease, suppressive action of high iodide may persist

Question 7

T3 & T4 hormones circulate bound to which plasma protein ?

A	Thyroxine-binding globulin (TBG)
B	Transthyretin (TTR)
C	Albumin
D	All of the above

Question 7 Explanation:

T4 & T3 are bound to plasma proteins which include thyroxine-binding globulin (TBG), transthyretin (TTR, formerly known as thyroxine-binding prealbumin, or TBPA) and albumin.

Question 8

Function of serum-binding proteins is ?

A	To increase pool of circulating hormone
B	To delay hormone clearance
C	To modulate hormone delivery
D	All of the above

Question 8 Explanation:

Plasma-binding proteins increase the pool of circulating hormone, delay hormone clearance, and may modulate hormone delivery to selected tissue sites.

Question 9

Which of the following receptors mediate thyroglobulin (Tg) endocytosis by thyroid cells ?

A	Cubilin
B	Clathrin
C	Megalin
D	Adaptin

Question 9 Explanation:

Megalin is a transmembrane glycoprotein that mediates endocytosis of Tg by thyroid cells resulting in its transcytosis, thereby avoiding the lysosomal pathway, where proteolytic cleavage of Tg results in hormone release. Transcytosis of Tg endocytosed from the colloid is thought to be one of the mechanisms that account for the presence of intact Tg in the circulation, where the

Question 10

Megalin is also known as ?

A	gp280
B	gp310
C	gp330
D	gp360

Question 10 Explanation:

Megalin was originally identified as the antigen in Heymann nephritis of rats. It was purified from rat kidney brush border & named gp330 on the basis of molecular weight as estimated by its mobility during gel electrophoresis

Question 11

Megalin belongs to which of the following ?

A	LDL-receptor family
B	Toll-like receptor family
C	EGF receptor family
D	Secretin receptor family

Question 11 Explanation:

Megalin belongs to the LDL-receptor family, sharing common features with LDL receptor, LDLreceptor- related protein (LRP), very-low-density lipoprotein (VLDL) receptor, and the apolipoprotein E (apo E) receptor-2.

Question 12

Homeostatic mechanisms regulating thyroid axis are directed toward maintenance of normal concentrations of ?

A	Unbound T3 and T4
B	Protein bound T3 and T4
C	TSH
D	TRH

Question 12 Explanation:

Homeostatic mechanisms that regulate the thyroid axis are directed toward maintenance of normal concentrations of unbound hormones.

Question 13

In X-linked Thyroxine-binding globulin (TBG) deficiency, patients are ?

A	Hypothyroid
B	Hyperthyroid
C	Euthyroid
D	Any of the above

Question 13 Explanation:

X-linked TBG deficiency is associated with very low levels of total T4 and T3. However, because unbound hormone levels are normal, patients are euthyroid and TSH levels are normal. Efforts to normalize total T4 levels should be avoided, as it may lead to thyrotoxicosis.

Question 14

Which of the following statements about familial dysalbuminemic hyperthyroxinemia (FDH) is false ?

A	Due to mutations in albumin
B	Autosomal dominant transmission
C	Increased total T4 &/or T3, but free hormone levels are normal
D	TSH levels are decreased

Question 14 Explanation:

Mutations in TBG, TTR, and albumin may increase the binding affinity for T4 and/or T3 and cause disorders known as euthyroid hyperthyroxinemia or familial dysalbuminemic hyperthyroxinemia (FDH). Total T4 and/or T3 are increased but unbound hormone levels are normal. Familial nature with normal TSH levels suggest this diagnosis. Unbound hormone levels (ideally measured by dialysis) are normal in FDH.

Question 15

Acquired TBG excess occurs due to all except ?

A	Pregnancy
B	CHF
C	Cirrhosis
D	Hepatitis

Question 15 Explanation:

Acquired TBG excess is seen with estrogen, pregnancy, cirrhosis & hepatitis.

Question 16

Which of the following about deiodinases is false ?

A	T4 is converted to T3 by deiodinase enzymes
B	Type I deiodinase is located in thyroid, liver & kidney
C	Type I deiodinase has a relatively low affinity for T4
D	None of the above

Question 16 Explanation:

T4 is converted to T3 by deiodinase enzymes. Type I deiodinase, which is located primarily in thyroid, liver, and kidney, has a relatively low affinity for T4.

Question 17

Which of the following about deiodinases is false ?

A	Type II deiodinase is found in pituitary, brown fat, brain & thyroid
B	Type II deiodinase has higher affinity for T4
C	Type III deiodinase inactivates T4 & T3
D	None of the above

Question 17 Explanation:

Type II deiodinase has a higher affinity for T4 and is found primarily in the pituitary gland, brain, brown fat, and thyroid gland. Expression of type II deiodinase allows it to regulate T3 concentrations locally. Type III deiodinase inactivates T4 and T3.

Question 18

Type I deiodinase is located in all except ?

A	Thyroid
B	Liver
C	Prostate
D	Kidney

Question 18 Explanation:

Type I deiodinase is located primarily in thyroid, liver, and kidney.

Question 19

Which of the following deiodinases is the most important source of reverse T3 (rT3) ?

A	Type I deiodinase
B	Type II deiodinase
C	Type III deiodinase
D	All of the above

Question 19 Explanation:

Type III deiodinase inactivates T4 and T3 and is the most important source of reverse T3 (rT3). Massiv

Question 20

T4 to T3 conversion may be impaired by ?

A	Fasting
B	Systemic illness
C	Acute trauma
D	All of the above

Question 21

T4 to T3 conversion may be impaired by ?

A	Oral contrast agents
B	Amiodarone
C	Glucocorticoids
D	All of the above

Question 21 Explanation:

T4 to T3 conversion is impaired by fasting, systemic illness or acute trauma, oral contrast agents, and medications like propylthiouracil, propranolol, amiodarone, glucocorticoids

Question 22

Which of the following is a thyroid hormone (TH) transporter ?

A	MCT2
B	MCT4
C	MCT6
D	MCT8

Question 22 Explanation:

Circulating thyroid hormones enter cells by passive diffusion and via the monocarboxylate 8 (MCT8) transporter. Mutations in MCT8 cause neurologic deficits & thyroid function abnormalities (low T4, high T3, and high TSH).

Question 23

Which of the following X-Linked Syndromes is related to mutation in MCT8 gene ?

A	Gustavsson syndrome
B	Brooks-Wisniewski-Brown syndrome
C	Allan-Herndon-Dudley syndrome
D	Schimke syndrome

Question 23 Explanation:

Allan-Herndon-Dudley syndrome is an X-linked mental retardation condition caused by mutations in the monocarboxylate transporter 8 (MCT8) gene. Its features include moderate-severe mental retardation, impaired speech, hypotonia, muscle weakness, and contractures. Mutations in this gene, located at Xq13.2, impair transport of T3 into neurons (elevated free T3 & decreased free T4 in blood).

Question 24

Thyroid hormones act through ?

A	Cell membrane hormone receptors
B	Nuclear hormone receptors
C	Mitochondrial hormone receptors
D	All of the above

Question 24 Explanation:

Thyroxine (T4) and triiodothyronine (T3) act through nuclear receptors.

Question 25

Thyroid hormone receptor  (TRis more abundant than TR in which of the following organs ?

A	Brain
B	Kidney
C	Gonads
D	Pituitary

Question 26

Thyroid hormone receptor  (TRis more abundant than TR in which of the following organs ?

A	Muscle
B	Kidney
C	Liver
D	Heart

Question 26 Explanation:

Thyroid hormones bind with high affinity to nuclear thyroid hormone receptors (TR) alpha & beta - expressed in most tissues. TR-alpha is particularly abundant in brain, kidney, gonads, muscle, and heart, whereas TR - beta expression is relatively high in the pituitary and liver.

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Disorders of the Thyroid Gland- Part 1| Disorders of the Thyroid Gland- Part2| Disorders of the Thyroid Gland- Part 3| Disorders of the Thyroid Gland- Part 4| Disorders of the Thyroid Gland- Part 5

1 In iodine-sufficient populations, urinary iodine is level is ?
A. > 2 μg/dL
B. > 5 μg/dL
C. > 8 μg/dL
D. > 10 μg/dL

2 Thyroglobulin releases T4 & T3 in which structure of thyroid
cell ?
A. Mitochondria
B. Golgi apparatus
C. Lysosome
D. All of the above

3 Which of the following is false about thyroglobulin (Tg) ?
A. 660 kDa size
B. Dimeric protein
C. Consists of 2769 amino acids
D. None of the above

4 Congenital hypothyroidism is mostly due to mutations in ?
A. TPO

B. NIS
C. Dehalogenase
D. Pendrin

5 Factors that influence thryoid hormone synthesis & release include
all except ?
A. Insulin-like growth factor I (IGF-I)
B. Prolactin
C. Epidermal growth factor
D. Transforming growth factor  (TGF-)

6 Wolff-Chaikoff effect is related to ?
A. Iodine deficiency
B. Excess iodide
C. Developmental abnormality of thyroid
D. All of the above

7 T3 & T4 hormones circulate bound to which plasma protein ?
A. Thyroxine-binding globulin (TBG)
B. Transthyretin (TTR)
C. Albumin
D. All of the above

8 Function of serum-binding proteins is ?
A. To increase pool of circulating hormone
B. To delay hormone clearance
C. To modulate hormone delivery
D. All of the above

9 Which of the following receptors mediate thyroglobulin (Tg)
endocytosis by thyroid cells ?
A. Cubilin
B. Clathrin
C. Megalin
D. Adaptin

10 Megalin is also known as ?
A. gp280
B. gp310
C. gp330
D. gp360

11 Megalin belongs to which of the following ?
A. LDL-receptor family
B. Toll-like receptor family
C. EGF receptor family
D. Secretin receptor family

12 Homeostatic mechanisms regulating thyroid axis are directed
toward maintenance of normal concentrations of ?
A. Unbound T3 and T4
B. Protein bound T3 and T4
C. TSH
D. TRH

13 In X-linked Thyroxine-binding globulin (TBG) deficiency, patients
are ?
A. Hypothyroid
B. Hyperthyroid
C. Euthyroid
D. Any of the above

14 Which of the following statements about familial dysalbuminemic
hyperthyroxinemia (FDH) is false ?
A. Due to mutations in albumin
B. Autosomal dominant transmission
C. Increased total T4 &/or T3, but free hormone levels are normal
D. TSH levels are decreased

15 Acquired TBG excess occurs due to all except ?
A. Pregnancy
B. CHF
C. Cirrhosis

D. Hepatitis

16 Which of the following about deiodinases is false ?
A. T4 is converted to T3 by deiodinase enzymes
B. Type I deiodinase is located in thyroid, liver & kidney
C. Type I deiodinase has a relatively low affinity for T4
D. None of the above

17 Which of the following about deiodinases is false ?
A. Type II deiodinase is found in pituitary, brown fat, brain &
thyroid
B. Type II deiodinase has higher affinity for T4
C. Type III deiodinase inactivates T4 & T3
D. None of the above

18 Type I deiodinase is located in all except ?
A. Thyroid
B. Liver
C. Prostate
D. Kidney

19 Which of the following deiodinases is the most important source
of reverse T3 (rT3) ?
A. Type I deiodinase
B. Type II deiodinase
C. Type III deiodinase
D. All of the above

20 T4 to T3 conversion may be impaired by ?
A. Fasting
B. Systemic illness
C. Acute trauma
D. All of the above
21 T4 to T3 conversion may be impaired by ?
A. Oral contrast agents
B. Amiodarone
C. Glucocorticoids
D. All of the above

22 Which of the following is a thyroid hormone (TH) transporter ?
A. MCT2
B. MCT4
C . MCT6
D. MCT8

23 Which of the following X-Linked Syndromes is related to mutation
in MCT8 gene ?
A. Gustavsson syndrome
B. Brooks-Wisniewski-Brown syndrome
C. Allan-Herndon-Dudley syndrome
D. Schimke syndrome

24 Thyroid hormones act through ?
A. Cell membrane hormone receptors
B. Nuclear hormone receptors
C. Mitochondrial hormone receptors
D. All of the above

25 Thyroid hormone receptor  (TRis more abundant than TR
in which of the following organs ?
A. Brain
B. Kidney
C. Gonads
D. Pituitary
26 Thyroid hormone receptor  (TRis more abundant than TR
in which of the following organs ?
Harrison’s 18th Ed. 2915
A. Muscle
B. Kidney
C. Liver
D. Heart

Disorders of the Thyroid Gland

[MCQ] Disorders of the Thyroid Gland- Part 2

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Disorders of the Thyroid Gland- Part 2

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