Term
| What are the general effects of thyroid hormone? |
|
Definition
Increases oxygen utilization
Increases energy expenditure
Increases heat production |
|
|
Term
| What is the structure of the thyroid? |
|
Definition
| Glandular with many follicles filled with colloid. |
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|
Term
| What is the main component of colloid? |
|
Definition
| Predominately made up of the protein thyroglobulin |
|
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Term
| What is the purpose of Thyroglobulin? |
|
Definition
| It serves at the backbone for the thyroid hormones, which are iodinated derivates of tyrosine. |
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Term
1. What is the dietary intake of Iodide daily?
2. How much Iodide does the thyroid store?
3. How much does Iodide does the thyroid take up daily? |
|
Definition
1. 400 μg
2. 8000 μg
3. 80 μg |
|
|
Term
| What is the Wolf-Chaikoff Effect? |
|
Definition
| If iodide intake exceeds 2mg/day, excess iodide in the thyroid inhibits the iodide trap and hormone synthesis. |
|
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Term
| How does the thyroid retain iodine? |
|
Definition
| By conjugating it to tyrosines on thyroglobulin. |
|
|
Term
| What are the two major thyroid hormones that are synthesized from thyroglobulin? |
|
Definition
|
|
Term
| How does iodide transport across the basolateral membrane of the thyroid follicular cell? |
|
Definition
|
|
Term
|
Definition
| The coupling of transported iodide to thyroglobuin in the lumen of the thyroid which traps the iodide within the gland |
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|
Term
| How does iodide exit the follicular cell of the tyroid? |
|
Definition
| Via the anion exchanger, Pendrin in a secretory vesicle with Thyroid Peroxidase. |
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|
Term
| What is the purpose of Thyroid Peroxidase (TPO)? |
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Definition
| In the presence of H2O2 it converts Iodide into Iodine. It also catalyzes the coupling of iodine to certain tyrosines on secreted thyroglobulin. |
|
|
Term
| T/F: When Iodide is limiting, T3 production is favored over T4. |
|
Definition
|
|
Term
1. How are T3 and T4 stored?
2. How are they released? |
|
Definition
1. Stored as a colloid in the lumen formed by follicular cells.
2. Colloid is endocytosed into the follicular cell. Lysosomes release the hormone from the colloid and T3 and T4 transit the basal membrane into the circulatory system. |
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|
Term
| What is the major binding protein for thyroid hormones? |
|
Definition
| Thyroxine-Binding Globulin (TBG). Most T3 and T4 are bound to proteins in the circulation. |
|
|
Term
| What is the activity of the thyroid hormones from greatest to least? |
|
Definition
T3>T4>rT3
Only FREE T3 and T4 are active. |
|
|
Term
| Where does the conversion of T4 to T3 occur? |
|
Definition
| In the peripheral tissues |
|
|
Term
| Where do T3 and T4 bind in the cell? |
|
Definition
After passive diffusion into the cell, most T4 is converted into T3 and binds to Thyroid Hormone Receptor (TR)
. |
|
|
Term
| What is bound to Thyroid Binding Receptor (TR) when T3 and T4 are unavailable? |
|
Definition
| Thyroid Regulatory Elements (TRE) which repress gene expression downstream from the receptor. |
|
|
Term
| What are the structures of TR? |
|
Definition
| Homodimer or Heterodimer of TR and RXR |
|
|
Term
| What is the hormonal regulation of thyroid hormones? |
|
Definition
Hypothalamus: TRH
Anterior Pituitary: TSH |
|
|
Term
| What does TSH receptor activation result in? |
|
Definition
Thyroglobulin and Peroxidase Synthesis
Iodide Trapping
T3 and T4 synthesis
colloid endocytosis
T3, T4 release
Thyroid Gland development |
|
|
Term
| How does TSH deficiency affect thyroid size? |
|
Definition
|
|
Term
| What is the feedback for thyroid hormones? |
|
Definition
T3 and T4 inhibit TSH and TRH release
TSH inhibits TRH release |
|
|
Term
What cells are targeted with thyroid hormones?
What are their actions? |
|
Definition
Almost all cells
They regulate normal growth, development and metabolism |
|
|
Term
| What is the effect of thyroid hormone on basal metabolic rate? |
|
Definition
|
|
Term
| What is the effect of thyroid hormones on fat metabolism? |
|
Definition
| It increases it increasing the concentration of fatty acids in the plasma. |
|
|
Term
| Thyroid Hormone levels are _________ related to cholesterol and triglyceride levels |
|
Definition
| Inversely. Hypothyroidism (low T3, T4) correlates with increased plasma cholesterol. |
|
|
Term
What is a goiter?
How does size of gland reflect functioning? |
|
Definition
| An enlargement of the thyroid. Presence of the thyroid does not reflect function. |
|
|
Term
| What is the effect of a iodine deficiency? |
|
Definition
| Causes a decrease in thyroid hormone. When it is severe, the individual will be hypothyroid with goiter. |
|
|
Term
|
Definition
| If iodine deficiency is not extreme, the tyroid will increase iodine trapping in order to maintain normal T4 serum levels. |
|
|
Term
| What is the pathphysiology with Grave's Disease? |
|
Definition
| This is a hyperthyroidism caused by abnormal antibodies binding and stimulating TSH receptors in the thyroid gland increasing synthesis and secretion of thyroid hormones. |
|
|
Term
What are the symptoms with Hypothyroidsm in children?
Treatment? |
|
Definition
Respiratory Distress Syndrome, Poor Feeding, Hoarse Cry, Retarded Bone Age
Replacement therapy of hormone |
|
|
Term
What are the symptoms with Hypothyroidsm in adults?
Treatment? |
|
Definition
Decreased basal metabolic rate, hypothermia, reduced cold tolerance, reduced cardiac output, hypertensive
Replacement therapy |
|
|
Term
| What are some causes of Adult Hypothyroidism? |
|
Definition
Gland destruction
Autoimmune disease
Iodine deficiency
Thyroiditis |
|
|
Term
| What is Hashimoto's Thyroiditis? |
|
Definition
| Autoimmune antibodies target TPO and TG causing hypothyroidism. |
|
|
Term
| What are the symptoms of hyperthyroidism (Grave's Disease)? |
|
Definition
| Increased basal metabolic rate, heat production, heat intolerance, nervousness, palpitations |
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