Podcast
Questions and Answers
What is the first-line treatment for hypothyroidism?
What is the first-line treatment for hypothyroidism?
What autoimmune disease is commonly associated with hyperthyroidism?
What autoimmune disease is commonly associated with hyperthyroidism?
Which of the following symptoms is NOT typically associated with hyperthyroidism?
Which of the following symptoms is NOT typically associated with hyperthyroidism?
Which treatment aims to block the conversion of T4 to T3 in hyperthyroidism?
Which treatment aims to block the conversion of T4 to T3 in hyperthyroidism?
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What level decreases in the blood due to hyperthyroidism?
What level decreases in the blood due to hyperthyroidism?
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What is the primary function of the follicular cells in the thyroid gland?
What is the primary function of the follicular cells in the thyroid gland?
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What are the two main hormones produced by the thyroid gland?
What are the two main hormones produced by the thyroid gland?
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Which process involves the iodination of tyrosine residues in the thyroid?
Which process involves the iodination of tyrosine residues in the thyroid?
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How does the thyroid gland concentrate iodine?
How does the thyroid gland concentrate iodine?
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What structural change occurs in acinar cells during hyperactivity of the thyroid gland?
What structural change occurs in acinar cells during hyperactivity of the thyroid gland?
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What is formed when monoiodotyrosine (MIT) couples with diiodotyrosine (DIT)?
What is formed when monoiodotyrosine (MIT) couples with diiodotyrosine (DIT)?
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Which condition describes the structural appearance of inactive acinar cells?
Which condition describes the structural appearance of inactive acinar cells?
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What role do parafollicular cells have in the thyroid gland?
What role do parafollicular cells have in the thyroid gland?
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Which thyroid hormone is considered more active and has a faster effect?
Which thyroid hormone is considered more active and has a faster effect?
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What is the primary source of T3 in the body?
What is the primary source of T3 in the body?
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What is the duration of the half-life of T4 in the blood?
What is the duration of the half-life of T4 in the blood?
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Which of the following is a common symptom of hypothyroidism?
Which of the following is a common symptom of hypothyroidism?
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What happens to the thyroid gland in response to iodine deficiency?
What happens to the thyroid gland in response to iodine deficiency?
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In the condition known as cretinism, what is the likely cause?
In the condition known as cretinism, what is the likely cause?
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How does T3 affect protein synthesis in cells?
How does T3 affect protein synthesis in cells?
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What is a distinguishing feature of Hashimoto's thyroiditis?
What is a distinguishing feature of Hashimoto's thyroiditis?
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What is the consequence of untreated congenital hypothyroidism?
What is the consequence of untreated congenital hypothyroidism?
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Which thyroid hormone is bound more in the blood?
Which thyroid hormone is bound more in the blood?
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Which hormones are predominantly secreted by the thyroid gland?
Which hormones are predominantly secreted by the thyroid gland?
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What is the major function of Thyrotropin-releasing hormone (TRH) in thyroid hormone regulation?
What is the major function of Thyrotropin-releasing hormone (TRH) in thyroid hormone regulation?
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What role does calcitonin play in the body?
What role does calcitonin play in the body?
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Which of the following is NOT a general effect of thyroid hormones?
Which of the following is NOT a general effect of thyroid hormones?
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What mechanism regulates the secretion of TSH?
What mechanism regulates the secretion of TSH?
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Which type of cells is responsible for the uptake and digestion of colloid in the thyroid?
Which type of cells is responsible for the uptake and digestion of colloid in the thyroid?
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Which of the following actions is primarily attributed to thyroid hormones?
Which of the following actions is primarily attributed to thyroid hormones?
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What percentage of circulating T4 and T3 is free and unbound in the bloodstream?
What percentage of circulating T4 and T3 is free and unbound in the bloodstream?
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Which of the following hormones primarily binds to thyroxine-binding globulin in circulation?
Which of the following hormones primarily binds to thyroxine-binding globulin in circulation?
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What is the main site of action for thyroid hormones in the body?
What is the main site of action for thyroid hormones in the body?
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Study Notes
Thyroid Gland Overview
- The thyroid gland is a large endocrine gland, weighing 18-60g in adults.
- Its location is caudal to the larynx, adhering to the front of the trachea.
- It's shaped like a shield (Greek: "shield-like").
- The gland concentrates iodine from the blood stream.
- It's composed of two lobes connected by an isthmus.
Thyroid Hormone Production
- Follicular cells produce thyroid hormones (T3 and T4).
- Follicular cells trap iodine actively against a concentration gradient, using Na+/I- symporters.
- Thyroglobulin (TGB) is produced and stored in the colloid.
- Tyrosine in TGB is iodinated to form MIT and DIT.
- MIT and DIT couple to form T3 and T4.
- Thyroid hormones are released into the blood.
- T4 is largely a prohormone and is converted to T3 outside the thyroid.
Thyroid Hormone Regulation
- The hypothalamus produces TRH.
- TRH stimulates the anterior pituitary to release TSH.
- TSH stimulates the thyroid gland to produce more hormones.
- High T3 and T4 levels inhibit TRH and TSH release.
Actions of Thyroid Hormones
- T3 andT4 increase the metabolic rate.
- They enhance protein synthesis, breakdown of fats, and glucose usage in ATP production.
- They affect nervous system maturation during fetal development and modulate heart rate.
- Calcitonin, produced by C-cells, regulates bone building.
Thyroid Diseases
- Hypothyroidism: Reduced hormone production. Symptoms include slow metabolic rate, weight gain, fatigue, and cold intolerance. It can be treated with T4 replacement therapy. Causes include iodine deficiency, autoimmune (Hashimoto's) attack, or congenital defects.
- Hyperthyroidism: Excess hormone production. Symptoms include elevated metabolic rate, weight loss, anxiety, heat intolerance, and rapid heart rate. It can be treated using antithyroid medications, radioactive iodine, or surgery. Common causes are Graves' disease (autoimmune) or toxic nodules.
- Goiter: Enlarged thyroid gland, often a symptom of iodine deficiency.
- Thyroid nodules: Growths often benign and cause either over or underactive thyroid function.
Importance of Thyroid Hormones
- Thyroid hormones are vital for normal growth and development throughout life.
- They are essential for many body tissues and have actions at the cellular level (especially in the nucleus).
- Basal metabolic rate (BMR) is increased by thyroid hormones in adults.
Thyroid Hormone Properties
- Most thyroid hormone is secreted as T4 (80 µg/day). T3 is more active with a much faster rate of turnover and better receptor binding.
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Description
This quiz covers the anatomy and physiology of the thyroid gland, including its structure, hormone production, and regulatory mechanisms. Test your knowledge on key concepts such as T3 and T4 synthesis, and the roles of TRH and TSH in hormone regulation.