Physio- Thyroid Gland

Question 1

The epithelial cells lining the thyroid follicles primarily secrete which hormones?
A) Calcitonin and parathyroid hormone.
B) Thyroxine and calcitonin.
C) Triiodothyronine and calcitonin.
D) Thyroxine and triiodothyronine.
E) Thyroid-stimulating hormone and thyroxine.

Answer 1

D) Thyroxine and triiodothyronine.

Question 2

Calcitonin, a hormone involved in calcium regulation, is secreted by:
A) Follicular cells.
B) Parafollicular cells (C-cells).
C) Hypothalamic neurons.
D) Anterior pituitary cells. E) Cells lining the thyroid follicles.

Answer 2

B) Parafollicular cells (C-cells).

Question 3

The synthesis of thyroid hormones primarily involves the iodination of which amino acid?
A) Serine.
B) Glycine.
C) Tyrosine.
D) Alanine.
E) Phenylalanine.

Answer 3

C) Tyrosine.

Question 4

Which thyroid hormone is secreted in much greater amounts by the thyroid gland?
A) Triiodothyronine (T3).
B) Thyroxine (T4).
C) Reverse triiodothyronine (rT3).
D) Diiodotyrosine (DIT).
E) Monoiodotyrosine (MIT).

Answer 4

B) Thyroxine (T4).

Question 5

Which thyroid hormone is considered more potent at activating receptors in target cells?
A) Thyroxine (T4).
B) Triiodothyronine (T3).
C) Reverse triiodothyronine (rT3).
D) Diiodotyrosine (DIT).
E) Monoiodotyrosine (MIT).

Answer 5

B) Triiodothyronine (T3).

Question 6

The thyroid gland has a unique ability to accumulate large amounts of:
A) Sodium ions.
B) Potassium ions.
C) Chloride ions.
D) Iodide ions.
E) Calcium ions.

Answer 6

D) Iodide ions.

Question 7

The energy for iodide transport into the follicular cell against its concentration gradient is primarily derived from:
A) ATP hydrolysis directly coupled to iodide transport.
B) The Na+ gradient.
C) The K+ gradient.
D) The chloride gradient.
E) Mitochondrial oxidative phosphorylation.

Answer 7

B) The Na+ gradient.

Note: Iodide is transported via and active transport.

Question 8

The sodium-iodide symporter, responsible for iodide uptake, is located on the:
A) Apical membrane of the follicular cell.
B) Basolateral membrane of the follicular cell.
C) Luminal membrane of the follicle.
D) Endoplasmic reticulum.
E) Golgi apparatus.

Answer 8

B) Basolateral membrane of the follicular cell.

Question 9

Once inside the follicular cell, iodide is transported into the colloid space through a(n):
A) Sodium-potassium pump.
B) Iodide symporter.
C) Iodide channel.
D) Vesicular transport mechanism.
E) Ligand-gated channel.

Answer 9

C) Iodide channel.

Question 10

Along with iodide transport, follicular cells synthesize and release into the follicle lumen:
A) Thyroid-stimulating hormone and thyroglobulin.
B) Thyroxine and peroxidase.
C) Glycoprotein thyroglobulin and peroxidase.
D) Triiodothyronine and thyroglobulin.
E) Calcitonin and peroxidase.

Answer 10

C) Glycoprotein thyroglobulin and peroxidase.

Note: Peroxidase is the enzyme responsible for for the oxidation of iodide

Question 11

The process by which uncharged iodine reacts with tyrosine residues on thyroglobulin is known as:
A) Iodide uptake.
B) Proteolysis.
C) Oxidation.
D) Iodide organification.
E) Conjugation.

Answer 11

D) Iodide organification.

Question 12

The binding of one iodine atom to a tyrosine residue on thyroglobulin results in the formation of:
A) Diiodotyrosine (DIT).
B) Triiodothyronine (T3).
C) Thyroxine (T4).
D) Monoiodotyrosine (MIT).
E) Reverse triiodothyronine (rT3).

Answer 12

D) Monoiodotyrosine (MIT).

Question 13

The condensation of one molecule of monoiodotyrosine (MIT) with one molecule of diiodotyrosine (DIT) forms:
A) Thyroxine (T4).
B) Reverse triiodothyronine (rT3).
C) Triiodothyronine (T3).
D) Thyroglobulin.
E) Thyroid peroxidase.

Answer 13

C) Triiodothyronine (T3).

Note: 2 DIT forms T4.

Question 14

The release of T3 and T4 from the follicular colloid into the blood is primarily stimulated by:
A) Calcitonin.
B) Parathyroid hormone.
C) Thyroid-releasing hormone (TRH).
D) Thyroid-stimulating hormone (TSH).
E) Somatostatin.

Answer 14

D) Thyroid-stimulating hormone (TSH).

Question 15

The process by which colloid droplets containing iodinated thyroglobulin enter the follicular cells is:
A) Exocytosis.
B) Active transport.
C) Passive diffusion.
D) Pinocytosis.
E) Facilitated diffusion

Answer 15

D) Pinocytosis.

Question 16

The endocytic receptor on the luminal surface of the follicular cell that facilitates the uptake of colloid is:
A) The TSH receptor.
B) Thyroglobulin receptor.
C) Megalin.
D) Sodium-iodide symporter.
E) Iodide channel.

Answer 16

C) Megalin.

Question 17

Within the follicular cells, T4 and T3 are cleaved from thyroglobulin by:
A) Cytosolic enzymes.
B) Enzymes within the endoplasmic reticulum.
C) Lysosomal enzymes.
D) Enzymes in the Golgi apparatus.
E) Peroxidase.

Answer 17

C) Lysosomal enzymes.

Question 18

The secretion of thyroid-stimulating hormone (TSH) from the anterior pituitary is controlled by:
A) Thyroxine (T4).
B) Triiodothyronine (T3).
C) Thyrotropin-releasing hormone (TRH) from the hypothalamus.
D) Calcitonin from the thyroid gland.
E) Parathyroid hormone from the parathyroid glands.

Answer 18

C) Thyrotropin-releasing hormone (TRH) from the hypothalamus.

Question 19

The production of thyrotropin-releasing hormone (TRH) is increased under which of the following conditions?
A) Hyperthermia.
B) Hyperglycemia.
C) Stressful conditions.
D) Increased plasma levels of T3 and T4.
E) Exercise.

Answer 19

C) Stressful conditions.

Question 20

The secretion of both TSH and TRH is inhibited by high plasma levels of:
A) Calcitonin.
B) Parathyroid hormone.
C) Thyroxine (T4) and triiodothyronine (T3).
D) Iodide.
E) Thyroglobulin.

Answer 20

C) Thyroxine (T4) and triiodothyronine (T3).

Question 21

In the blood, the majority of thyroid hormones are transported:
A) As free hormones.
B) Bound to erythrocytes.
C) Bound to albumin.
D) Bound to transporting proteins.
E) Dissolved in the plasma.

Answer 21

D) Bound to transporting proteins.

Question 22

The primary thyroxine-binding protein in the blood is:
A) Albumin.
B) Transthyretin.
C) Thyroxine-binding globulin.
D) High-density lipoprotein (HDL).
E) Low-density lipoprotein (LDL).

Answer 22

C) Thyroxine-binding globulin.

Question 23

List the functions of the thyroid gland receptors.

Answer 23

Maintain circulatory resivore
Prevents loss of T3 and T4 w/ filtration of kidney
Prevents overstimulation of target cell by T3 and T4

Question 24

The physiological effects of thyroid hormones on target organs are primarily induced by:
A) Protein-bound T4.
B) Protein-bound T3.
C) Protein-free T4.
D) Protein-free T3.
E) Both protein-bound and protein-free hormones equally.

Answer 24

D) Protein-free T3.

Question 25

Prior to entering target cells, thyroid hormones must: A) Bind to cell surface receptors. B) Undergo further iodination. C) Dissociate from transporting proteins. D) Be metabolized by the liver. E) Be converted to inactive metabolites.

Answer 25

C) Dissociate from transporting proteins.

Question 26

The primary mechanism of action of triiodothyronine (T3) in target cells involves: A) Activation of cell surface enzymes. B) Stimulation of receptors localized in the cell membrane. C) Stimulation of the receptor localized in the nucleus of the cell. D) Modulation of ion channels. E) Activation of second messenger systems in the cytoplasm.

Answer 26

C) Stimulation of the receptor localized in the nucleus of the cell.

Question 27

Thyroid hormone receptors primarily mediate: A) Enzyme activation. B) Ion channel regulation. C) Gene transcription and protein synthesis. D) Second messenger signaling. E) Neurotransmitter release.

Answer 27

C) Gene transcription and protein synthesis.

Question 28

Deiodinases are enzymes responsible for: A) The synthesis of thyroglobulin. B) The transport of iodide into the follicular cell. C) The removal of iodine from the T4 molecule. D) The binding of thyroid hormones to plasma proteins. E) The degradation of thyroid hormone receptors.

Answer 28

C) The removal of iodine from the T4 molecule.

Question 29

The removal of iodine from the outer benzyl ring of thyroxine (T4) results in the formation of: A) Reverse triiodothyronine (rT3). B) Triiodothyronine (T3). C) Diiodotyrosine (DIT). D) Monoiodotyrosine (MIT). E) Thyroglobulin.

Answer 29

B) Triiodothyronine (T3).

Question 30

Which type of deiodinase is primarily responsible for the activation of T4 to T3 in the liver and kidney? A) Type 2 deiodinase. B) Type 3 deiodinase. C) Type 1 deiodinase. D) All three types equally. E) None of the above.

Answer 30

C) Type 1 deiodinase. Liver, kidney and Thyroid gland Note: Type 2 also activates in the brain and thyroid gland.

Question 31

The removal of iodine from the INNER benzyl ring of thyroxine (T4) results in the formation of: A) Reverse triiodothyronine (rT3). B) Triiodothyronine (T3). C) Diiodotyrosine (DIT). D) Monoiodotyrosine (MIT). E) Thyroglobulin.

Answer 31

A) Reverse triiodothyronine (rT3).

Question 32

Which type of deiodinase is primarily responsible for the inactivation of T4 to T3 in the Fetus, placenta and brain? A) Type 2 deiodinase. B) Type 3 deiodinase. C) Type 1 deiodinase. D) All three types equally. E) None of the above.

Answer 32

B) Type 3 deiodinase.

Question 33

The primary physiological effect of thyroid hormones is to: A) Decrease basal metabolic rate. B) Increase basal metabolic rate. C) Decrease heart rate and contractility. D) Promote energy storage. E) Inhibit protein synthesis.

Answer 33

B) Increase basal metabolic rate.

Question 34

The increase of basal metabolic rate of thyroid hormones is primarily attributed to: A) Increased glycogen synthesis. B) Decreased lipolysis. C) Increased number of mitochondria in cells. D) Decreased oxidative phosphorylation. E) Inhibition of catabolic enzymes.

Answer 34

C) Increased number of mitochondria in cells. Note: Also, increase rate of oxidation phosphorylation and activation of cellular enzymes

Question 35

Thyroid hormones facilitate adrenergic effects within the cardiovascular system by: A) Decreasing the sensitivity to catecholamines. B) Down-regulating beta-adrenergic receptors. C) Up-regulating beta-adrenergic receptors. D) Inhibiting the release of norepinephrine and epinephrine. E) Decreasing cardiac output.

Answer 35

C) Up-regulating beta-adrenergic receptors. Note: This increases HR, cardiac contractility and increase systolic blood pressure

Question 36

In the developing nervous system, thyroid hormones play a crucial role in: A) Inhibiting neuronal migration. B) Promoting formation of synapses and myelinization of axons. C) Decreasing dendritic branching. D) Inducing neuronal apoptosis. E) Blocking the action of growth factors.

Answer 36

B) Promoting formation of synapses and myelinization of axons. Note: and dendrites

Question 37

Deficiency of thyroid hormones during fetal life and childhood can result in: A) Increased height and advanced skeletal development. B) Mental retardation and short stature. C) Increased basal metabolic rate. D) Decreased appetite and weight gain. E) Hypertension and bradycardia.

Answer 37

B) Cretinism — Mental retardation and short stature.

Question 38

In the developing skeletal system, thyroid hormones play a crucial role in:

Answer 38

Promoting bone calcification Synthesis of bone proteins Bone growth Secretion of growth hormone

Question 39

Decrease production of thyroid hormones presents what clinical manifestations?

Answer 39

Mental retardation Short statue Immature skeletal bone development

Question 40

Primary hyperthyroidism is characterized by: A) Low plasma levels of T3 and T4, and high TSH. B) High plasma levels of T3 and T4, and high TSH. C) High plasma levels of T3 and T4, and low TSH. D) Low plasma levels of T3 and T4, and low TSH. E) Normal plasma levels of T3 and T4, and high TSH.

Answer 40

C) High plasma levels of T3 and T4, and low TSH.

Question 41

Secondary hyperthyroidism is typically caused by a defect in the: A) Thyroid gland. B) Hypothalamus. C) Anterior pituitary. D) Adrenal gland. E) Liver.

Answer 41

C) Anterior pituitary. High T3, T4 and TSH but low thyrotrobin releasing hormone

Question 42

The most common clinical sign in both primary and secondary hyperthyroidism is: A) Exophthalmos. B) Bradycardia. C) Goiter. D) Weight gain. E) Cold intolerance.

Answer 42

C) Goiter.

Question 43

Explain the physiology of Graves’ disease.

Answer 43

1. Produces antibodies that attach to the TSH receptor thus mimicking the effect of TSH. 2. Antibody: Thyroid stimulation immunoglobulin. 3. Increases secretion of T3 and T4 W

Question 44

Exophthalmos, a clinical feature of hyperthyroidism, is primarily caused by: A) Increased lacrimal gland secretion. B) Compression of the optic nerve by the enlarged thyroid. C) Periorbital edema related to increased inflammatory cytokines. D) Decreased retro-orbital fat. E) Muscle weakness in the extraocular muscles.

Answer 44

C) Periorbital edema related to increased inflammatory cytokines.

Question 45

Primary hypothyroidism is characterized by: A) Low plasma levels of T3 and T4, and low TSH. B) High plasma levels of T3 and T4, and high TSH. C) Low plasma levels of T3 and T4, and high TSH. D) High plasma levels of T3 and T4, and low TSH. E) Normal plasma levels of T3 and T4, and low TSH.

Answer 45

C) Low plasma levels of T3 and T4, and high TSH. Note: Secondary — low plasma levels of T3, T4 and TSH (anterior pituitary)

Question 46

The most common cause of primary hypothyroidism in adult life is: A) Dietary iodine deficiency. B) Pituitary adenoma. C) Hashimoto thyroiditis. D) Surgical ablation of the thyroid. E) Radioactive iodine therapy for hyperthyroidism.

Answer 46

C) Hashimoto thyroiditis. Note: Myoedema

Question 47

List 2 other common cause of primary hypothyroidism in adult life is:

Answer 47

Surgical or radioactive abolition of thyroid gland Destruction of thyroid gland

Question 48

List the clinical manifestations of hypothyroidism.

Answer 48

Decrease body temperature Intolerance to cold Dry and rough skin Coarse hair Weight gain Muscle wasting Decrease appetite Decrease HR and BP Bradycardia Decrease protein synthesis Slow reflex, speech, apathy

Question 49

List the clinical manifestations of hyperthyroidism.

Answer 49

Increase body temperature Sweating Skin: warm and moist Heat intolerance Nervous: anxiety, tremors, nervousness Weight lost and muscle weakness Increase appetite Diarrhea Tachycardia Palpations