17 Questions
What is the approximate daily secretion of T3 by the human thyroid gland?
4 μg
Which of the following is true about free thyroid hormones in plasma?
They are in equilibrium with protein-bound thyroid hormones
What is the normal total plasma T4 level in adults approximately?
8 μg/dL
Which thyroid hormone is relatively lipophilic and has free forms in plasma that are physiologically active?
T3
How do free thyroid hormones contribute to the regulation of TSH secretion?
By inhibiting pituitary secretion of TSH
What is the main function of the thyroid gland?
Secreting calcitonin to regulate calcium levels
How is thyroglobulin secreted into the colloid in the thyroid gland?
By exocytosis of granules
What enzyme mediates the oxidation and reaction of iodide with thyroglobulin?
Thyroid peroxidase
What happens to the thyroid hormones produced by the thyroid gland until they are needed?
They remain part of the thyroglobulin molecule in the colloid
What is the first product formed in the thyroid hormone synthesis process?
Monoiodotyrosine (MIT)
How is T3 formed in the thyroid hormone synthesis process?
Condensation of MIT with DIT
Which component serves as a reservoir of thyroid hormones in the thyroid gland?
Colloid
What could happen if a person ingests a diet completely devoid of iodide for a long time?
Decline in circulating thyroid hormone levels
Which enzyme generates reactive iodine species for attacking thyroglobulin in the thyroid hormone synthesis process?
Thyroid peroxidase
What compound is formed by the condensation of DIT with MIT in the thyroid hormone synthesis process?
Reverse T3 (RT3)
What is the average distribution of T4 in the normal human thyroid from iodinated compounds?
35%
Which theory explains the coupling reaction where both DIT molecules are attached to thyroglobulin?
Intramolecular coupling theory
Test your knowledge on the thyroid gland and its role in the endocrine system. Explore the process of thyroid hormone synthesis, including the steps involved in iodination and hormone production.
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