24 Questions
What is the enzyme responsible for catalyzing the binding of iodine with thyroglobulin?
Thyroid peroxidase
What is the approximate percentage of T4 bound to thyroxin binding globulin (TBG) in the circulation?
80%
What is the half-life of T4 in the blood?
6 days
What is the main function of thyroid hormone receptor in the nucleus?
To influence transcription of genes
What is the fate of most of T4 in the targeted tissues?
It is deiodinated to T3 by iodinase enzyme
What is the approximate percentage of free T4 in the circulation?
0.03%
Where is the thyroid gland located?
Below the larynx on either sides and anterior to the trachea
What percentage of thyroid hormones is T4?
90%
What is the function of the iodide pump?
To actively transport iodide into the thyroid gland
What is the result of the coupling of MIT and DIT?
T3 and T4
What is the name of the enzyme responsible for the oxidation of iodide to iodine?
Thyroid peroxidase
What is the effect of administering a large amount of iodine on thyroid hormone levels?
A decrease in thyroid hormone levels
What percentage of T4 is converted to T3 before binding to the nuclear receptors?
90%
What is the effect of thyroid hormones on carbohydrate metabolism?
Increase glucose uptake by the cells
What is the overall effect of thyroid hormones on protein metabolism?
Catabolic leading to a decrease in muscle mass
What is the effect of thyroid hormones on peripheral resistance?
Decrease peripheral resistance
What is the effect of thyroid hormones on the heart rate?
Increase heart rate
What is the role of thyroid hormones in the prenatal period?
Essential for the maturation of the CNS
What is the effect of a decrease in thyroid hormone secretion on the central nervous system?
Slow movement and impaired memory
What is the role of tripeptide in the regulation of hormone secretion?
Releasing hormone that acts on the thyrotrophs
What is the effect of an increase in thyroid hormone secretion on the respiratory system?
Increased dissociation of oxygen from Hb
What is the role of thyrotropin-releasing hormone (TRH) in the regulation of hormone secretion?
Stimulates the release of TSH from the anterior pituitary
What is the effect of thyroid hormone on bone?
Promotes bone formation
What is the effect of a lack of thyroid hormone secretion on the gastrointestinal system?
Decreased digestive juice secretion
Test your understanding of the thyroid gland, its location, synthesis of thyroid hormones, control mechanisms, and the actions of T3 and T4 hormones. This quiz is based on Lecture 1 of Dr. Abdurrahman Muse Farah's Adal Medical Physiology course.
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