Multiple Choice Question on Thyroid Hormone Disorders and Function test




Thyroid Hormone Synthesis, Disorder, and Function Test- Multiple Choice Questions

1) Which of the following amino acid is the precursor for the synthesis of thyroid hormones?
a) Tryptophan
b) Tyrosine
c) Alanine
d) Proline

2) Which of the following form is the active form of thyroid hormone
a) T3
b) T4
c) rT3
d) None of the above

3) Which of the following proteins is the precursor for the thyroid hormone, and also a marker of thyroidal cancer?
a) Thyroalbumin
b) Thyroglobulin
c) Thyroid binding globulin
d) All of the above

4) The majority of the thyroid hormones in the blood are bound to proteins. Which of the following is not the thyroid hormone-binding proteins in the plasma?
a) Albumin
b) Thyroglobulin
c) Thyroid binding globulin
d) None of the above

5) Which of the following is the transporter responsible for the transport of iodine into the thyroid cells against the concentration gradient?
a) Na+ I- symport
b) K+ I- symport
c) I-/Cl- antiport
d) None of the above

6) Thyroperoxidase is an enzyme responsible for thyroid hormone synthesis. This enzyme catalyzes the following reaction except:
a) Conversion of iodide to iodine-free radical
b) Incorporation of iodine to a tyrosine residue of thyroglobulin
c) Condensation of monoiodotyrosine and diiodotyrosine
d) Cleavage and release of thyroid hormones

7) In addition to inhibiting thyroid hormone synthesis, which of the following chemical drug that also reduces the uptake of iodine into the thyroid cells?
a) Carbimazole
b) Methimazole
c) Thiourea
d) All of the above

8) The thyroid hormone synthesis is regulated by thyroid-stimulating hormone (TSH) synthesized by the anterior pituitary gland. The increased thyroid hormone synthesis is mediated by:
a) increased cGMP production in follicular cells
b) increased cAMP production in follicular cells
c) increased Ca+2 ions in the follicular cells
d) increased diacylglycerol production in follicular cells

9) Which of the following cellular processes increase in response to thyroid-stimulating hormones?
a) Uptake of iodide into the follicular cells
b) Synthesis of thyroglobulin proteins
c) Incorporation of iodide ions into tyrosine molecules of thyroglobulin
d) All of the above

10) The deiodinases are responsible for the removal of iodine from T4 molecules to produce T3 & rT3. Which of the type of the enzyme catalyzes the conversion of rT3?
a) Type I
b) Type II
c) Type III
d) None of the above

11) In pregnancy, TBG levels increase, leading to an increase in total thyroid hormone, but the normal levels of free hormone. This is known as
a) Euthyroid state
b) Hyperthyroid state
c) Hypothyroid state
d) Subclinical hypothyroid state

12) In peripheral tissues, T4 is converted to T3 by an enzyme
a) 5'-iodinase
b) 3'-iodinase
c) 5-iodinase
d) 3-iodinase

13) The hypothalamic-pituitary and thyroid axis regulates the synthesis and release of thyroid hormones. Which of the following receptors are down-regulated by excess T3
a) TSH receptor in the thyroid gland
b) T3 receptor in hypothalamus
c) TRH receptor in the anterior pituitary
d) All of the above

14) The patients with Graves disease have high circulating levels of thyroid hormones. The Graves disease is characterized by the following except
a) Excess release of TSH from the anterior pituitary
b) Hyperactivation of TSH receptor in thyroid glands
c) Presence of TSH receptor antibodies causing receptor activation
d) Decreased TSH levels

15) Which of the following is not the metabolic function of thyroid hormones
a) Glycogenolysis
b) Gluconeogenesis
c) Glucose oxidation
d) Glycogenesis

16) The metabolic function of thyroid hormones include
a) Decreased oxygen consumption
b) Increased lipogenesis
c) Increased Lipolysis
d) Protein Anabolism

17) A 50 years old man with hyperthyroidism is treated with propylthiouracil. The drug reduces the synthesis of thyroid hormones because it inhibits oxidation of
a) Triiodothyronine
b) Thyroxine
c) Diiodotyrosine
d) Iodide

18) Which of the following is the screening test for the diagnosis of thyroid disease
a) Thyroid Stimulating hormone
b) Total T3
c) Total T4
d) Free T3

19) The subclinical hyperthyroidism is characterized by
a) Increased TSH and normal free T3 & free T4 levels in the blood
b) Increased TSH and decreased free T3 & free T4 levels in the blood
c) Decreased TSH and normal free T3 & free T4 levels in the blood
d) Decreased TSH and increased free T3 and free T4 levels in the blood

20) A patient presents with tachycardia and heat intolerance and suspected of Graves disease. Which of the following is not a characteristic feature of  Grave disease
a) Increased total and free T4
b) Suppressed plasma TSH
c) Exophthalmos
d) Decreased thyroid radioactive iodine uptake



Answers
1-b) Tyrosine
2-a) T3
3-b) Thyroglobulin
4-b) Thyroglobulin
5-a) Na+ I- symport
6-d) Cleavage and release of thyroid hormones
7-a) Carbimazole
8-b) increased cAMP production in follicular cells
9-d) All of the above
10-c) Type III
11-a) Euthyroid state
12-a) 5'-iodinase
13-c) TRH receptor in the anterior pituitary
14-a) Excess release of TSH from the anterior pituitary
15- d) Glycogenesis
16-c) Increased Lipolysis
17-d) Iodide
18)-a) Thyroid Stimulating hormone
19-c) Decreased TSH and normal free T3 & free T4 levels in the blood
20-d) Decreased thyroid radioactive iodine uptake

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