32 Questions
What regulates circulating levels of calcium?
Calcitonin
Which enzyme is responsible for the oxidation and reaction of iodide in the thyroid gland?
Thyroid peroxidase
What is the function of thyrotropin releasing hormone (TRH) on thyroid hormone secretion?
Stimulates thyroid hormone secretion
What is the role of high circulating levels of thyroid hormones in the feedback control mechanism?
Control thyroid hormone secretion
What is the primary protein that most of the circulating T4 binds to?
Thyroxine-binding globulin (TBG)
Which protein has the shortest half-life among TBG, transthyretin, and albumin?
Transthyretin
What percentage of the circulating T4 is converted to T3 in adult humans?
33%
Which organ does not play a role in deiodinating T4 and T3?
Brain
What is a cause of congenital hypothyroidism according to the text?
Maternal antithyroid antibodies
How do drugs inhibit thyroid function according to the text?
By blocking iodide-trapping mechanism
What happens when dietary iodine intake falls below 50 μg/day according to the text?
The thyroid hypertrophies
How are hypothyroidism and goiter related according to the text?
Hypothyroidism leads to goiter
Which of the following compounds inhibit the iodination of monoiodotyrosine and block the coupling reaction in hyperthyroidism?
Propylthiouracil and methimazole
Which medication inhibits the conversion of T4 to T3 in many extrathyroidal tissues?
Propylthiouracil
What is the primary cause of hyperthyroidism in Hashimoto thyroiditis during the early stage?
Excess thyroid hormone secretion
How does radioactive iodine help in treating severe cases of hyperthyroidism?
It accumulates in the gland and partially destroys it
What is the function of calcitonin secreted by the thyroid gland?
Regulating circulating levels of calcium
How is thyroglobulin synthesized and secreted in the thyroid gland?
Exocytosis of granules
What enzyme mediates the oxidation and reaction of iodide with thyroglobulin in the thyroid gland?
Thyroid peroxidase
How long can humans go without dietary iodide before a decline in circulating thyroid hormone levels is observed?
2 months
Which plasma protein has the smallest capacity to bind T4 among albumin, transthyretin, and TBG?
TBG
What is the approximate daily secretion of T3 by the human thyroid?
4 μg (7 nmol)
In normal adult humans, what is the approximate plasma T3 level in μg/dL?
0.15
Which thyroid hormone is relatively lipophilic and has a larger pool of protein-bound forms in plasma and tissues?
T4
What is the initial product formed during thyroid hormone synthesis?
MIT
Which enzyme is responsible for generating reactive iodine species in the thyroid gland?
Thyroid peroxidase
How is T3 formed in the thyroid gland?
By condensation of MIT with DIT
What is the approximate percentage distribution of iodinated compounds in the normal human thyroid?
3% MIT, 33% DIT, 35% T4, 7% T3
What is the recommended treatment for iodide deficiency?
Adding iodized salt to the diet
Which of the following symptoms is NOT characteristic of hyperthyroidism?
Cold intolerance
How does hypothyroidism in the mother affect mental deficiency in offspring?
Results in more severe mental deficiency in offspring
What is the primary mechanism for treating congenital hypothyroidism soon after birth?
Administration of levothyroxine
Learn about the causes of hypothyroidism, including diseases of the thyroid gland, pituitary or hypothalamic failure, and conditions affecting thyroid function. Explore the specific causes of congenital hypothyroidism such as maternal iodine deficiency, fetal thyroid dysgenesis, and inborn errors of thyroid hormone synthesis.
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