This challenging quiz seeks to gauge your understanding of some trickier concepts in thyroid anatomy and physiology.  Good luck!

Reviewed by Jonathan Loomes-Vrdoljak on 3 October 2019

Thyroid Physiology MCQs

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Question 1
What is the classic origin of the inferior thyroid artery?
A
External carotid artery
B
Common carotid artery
C
A branch of the distal subclavian artery
D
The thyrocervical trunk
Question 2
Occlusion of which of the following structures would cause inferior thyroid vein drainage obstruction?
A
The external jugular vein
B
The internal jugular vein
C
The brachiocephalic trunk
D
The brachiocephalic vein
Question 3
Which of the following is true of the superior thyroid artery?
A
It travels adjacent to the sensory supply of the infraglottic compartment
B
It supplies the cricoid cartilage
C
It courses around the pyramidal lobe
D
It arises superior to the level of C4
Question 4
A consequence of calcitonin release will be ...
A
To increase T3 production
B
To decrease the basal metabolic rate
C
To increase NPT2A functionality
D
To increase circulating hormone derived from endocrine chief cells
Question 4 Explanation: 
Chief cells of the parathyroid gland secrete parathyroid hormone. It has an action antagonistic to calcitonin - namely to cause a release of bone calcium (amongst other stores) and to increase serum Ca++. As calcitonin acts to sequester calcium into stores away from the serum, the resultant drop in calcium levels causes the chief cells to release PTH to compensate. Do not confuse with gastric mucosa chief cells.
Question 5
A patient is to be scanned for radiolabeled iodine 24 hours after intravenous administration. Which of the following cell types will be accumulating tracer?
A
Oxyntic (parietal) cells
B
Chief cells
C
Follicular cells
D
C cells
Question 5 Explanation: 
The correct answer are the thyroid follicular cells. They “capture” iodide from the diet. C cells, aka parafollicular cells, primarily release calcitonin and play a negligible role in iodide sequestration. The remaining options are gastric cells, not relevant. NB: there are chief cells in the thyroid and gastrointestinal tract with different anatomy and physiology.
Question 6
Iodide is “trapped” in thyroid parenchyma using which form of transport?
A
Passive
B
Primary active
C
Secondary active
D
Voltage gated
Question 6 Explanation: 
In a secondary active transport, energy is used to transport a substance across a cell membrane. Unlike primary active transport, ATP is not directly involved, rather its metabolically-intensive process at another site causes an electrochemical gradient that is used in secondary active transport. Be familiar with the terms of membrane transport in human physiology.
Question 7
Which of the following is the poorest source of iodine?
A
Salt
B
Cod
C
Apples
D
Ground black pepper
Question 7 Explanation: 
Fruit, vegetables, salt and seafood are all high in dietary iodine. Indeed in landlocked regions, or areas of high altitude, deficiency of iodine is relatively common.
Question 8
Pendrin’s functionality can best be described as
A
A symporter on the apical parafollicular cell membrane
B
An antiporter on the apical parafollicular cell membrane
C
A symporter on the apical follicular cell membrane
D
An antiporter on the basolateral follicular cell membrane
Question 9
Correct conjugation in the follicular lumen of DIT + DIT will form?
A
The thyroid hormone macromolecule in circulatory majority
B
The most potent form of circulating thyroid hormone
C
Diiodothyronine
D
RT3
Question 9 Explanation: 
DIT + DIT conjugation forms T4. This is, whilst the least potent form of thyroid hormone, the form that is most prevalent in the serum. As such, T4 measurements are routinely preferred to T3 for thyroid function testing. At the target cell, eg the placenta, a deiodinase enzyme converts T4 to its more potent T3 variant, or RT3, for intracellular nuclear transcription regulation to occur.
Question 10
Which of the following peptides lack a similar structure
A
ACTH
B
TSH
C
LH
D
FSH
Question 11
TBG has a higher affinity for
A
T4
B
Albumin
C
Triiodothyronine
D
T3
Question 12
Which of the following deiodinase classes are upregulated in the gravid uterus?
A
Class I
B
Class II
C
Class III
D
Class IV
Question 13
Where does triiodothyronine exert its effect on BMR?
A
A GPCR
B
MCT8
C
Nuclear receptor
D
Transmembrane receptor
Question 14
At which stage in pregnancy is it possible for maternal follicular cells to assist in fetal neurogenesis?
A
First trimester
B
Second trimester
C
Third trimester
D
Fourth trimester
Question 15
Which physiological process best describes a patient with primary hyperthyroidism?
A
Increased NIS (sodium-iodide symporter) synthesis and expression
B
Increased follicular stimulating hormone (FSH)
C
Iodine deficiency
D
Decrease in the activity of the paraventricular nucleus
Question 15 Explanation: 
This is a relatively challenging question requiring several orders of thought and application of knowledge. If you felt confident with this answer, well done, if not that's fine. Revise the transport of substances into the follicular cells.
Question 16
On examination of the patient’s neck, a bilateral bruit is auscultated lateral to the proximal trachea.  
Which of the following is the more appropriate diagnosis?
A
Addison’s disease
B
Hyperparathyroidism
C
Hypothyroidism
D
Graves’ disease
Question 16 Explanation: 
The stem describes a thyroid bruit indicative of neovascularisation of a hypertrophic thyroid gland. As such, the most common form of hyperthyroidism - and an option here as it happens - is Graves’ disease.
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