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Physio Exam 5
Thyroid and Parathyroid
| Question | Answer |
|---|---|
| What cells are responsible for the production of the components of colloid | Epithelial cells |
| What are two important components of colloid | Thyroid hormone and thyroglobulin |
| Where are prafollicular (C cells) located in the thyroid | The interfollicular space and/or wall of the follicles |
| What do the parafollicular (C cells) produce | Calcitonin |
| What is colloid | The storage form of thyroid hormones |
| What stimulates the synthesis of thyroid hormone | Thyroid stimulating hormone released from the anterior pituitary glan d |
| What is thyroid hormone built from | Tyrosine residues of thyroglobulin that have been iodinated |
| If you add one iodine to the thyrosine residue you get | Monotyrosine (MIT) |
| If you add two idone groups to the thyrosine residue you get | Diiodotyrosine (DIT) |
| Are monotyrosine and diiodotyrosine active or inactive | Inactive |
| The coupling of a monotyrosine and a diiodotyrosine yields a | Triiodothyronine (T3) |
| What is the most active thyroid hormone | Triiodothyronine (T3) |
| What thyroid hormone is has the smallest concentration released | Triiodothyronine (T3) |
| The coupling of two diiodotyrosine yields a | Thyroxine (T4) |
| What is the primary secretory product of the thyroid gland | Thyroxine (T4) |
| What enzyme catalyzes the addition of iodine to the tyrosine residues of thyroglobulin to form DIT and MIT | Thyroperoxidase (TPO) |
| What enyzme provides the H2O2 needed for the addition of iodine to the tyrosine residues of | Thyroid oxidase |
| What catalzses the coupling of DIT and/or MIT to form T4 or T3 | Thyroid oxidase |
| What enzyme catalyzes the addition of iodine to the tyrosine residues of thyroglobulin to form DIT and MIT | Thyroperoxidase (TPO) |
| What enyzme provides the H2O2 needed for the addition of iodine to the tyrosine residues of | Thyroid oxidase |
| What catalzses the coupling of DIT and/or MIT to form T4 or T3 | Thyroid oxidase |
| How many types of thyroid hormone deiodinases are there | Three Types 1-3 |
| What reaction does type 1 thyroid hormone deiodinase catalyze | T4 --> T3 |
| Where is type 1 thyroid hormone deiodinase located | Liver, Kidney, Thyroid |
| What reaction does type 2 thyroid hormone deiodinase catalyze | T4 --> T3 |
| Where is type 2 thyroid hormone deiodinase located | Brain, BAT, pituitary, pineal, cardia and skeletal muscle, placenta |
| What stimulates the synthesis and secretion of thyroid hormone | Thyroid stimulating hormone |
| What is responsible for bringing iodide into the cell | NIS: sodium/iodide symporter |
| What protein does iodide leave the cell thru and enter the colloid | Pendrin |
| The endocytosis of colloid is stimulated by what | The biding of thyroid stimulating hormone to its receptor |
| How is T3 and T4 freed to be secreted from the cell | The endosome containing colloid fuses with a lysosome that breaks up the colloid |
| What reaction does type 3 thyroid hormone deiodinase catalyze | T3 --> T2 |
| Where is type 3 thyroid hormone deiodinase located | Brain, skin, placenta |
| What are the proteins that T3 and T4 bind for transport in order of decreasing affinity | Thyroxine binding globule > Transthyretin > Albumin |
| T3 and T4 bind what kind of receptor | Intracellular |
| T3 binds what nuclear receptor | Thyroid hormone receptor (TR) bound as a heterodimer with Retinoid X receptor |
| What happens when T3 binds the thyroid hormone receptor/retinoid X receptor heterodimer | The complex binds the the thyroid hormone-responsive gene, causing either an increase or decrease in the transcription of that gene |
| Why are T3 and T4 bound to protiens in circulation | To increase the half-life |
| What are the major effects of thyroid hormone | 1. Normal growth and metabolism 2. Overall oxygen utilization 3. Stimulation or inhibition of gene expression |
| What stimulates the release of thyroid hormone | Thyroid Stimulating hormone |
| What inhibits the release of thyroid hormone | T4 and T3 |
| Hyperthyroidism can be caused by | Grave's Disease |
| What is Grave's disease | An autoimmune disorder in which the TSH receptor antibody stimulates the thyroid gland |
| Hypothyroidism is caused by what | Hashimoto's disease, Damage (radiation post-op), Thyroiditis, Drugs (lithium) |
| What is Hasimoto's disease | An autoimmune disorder in which there are antibodies against the thyroid cells |
| Hyperthyroidism is also called | Thyrotoxicosis |
| What class of hormone is Calcitonin | Polypeptide |
| What cells produce Calcitonin | Parafollicular (C cells) |
| What other product besided calcitonin can be expressed due to alternate splicing | Calcitonin gene related peptide (CGRP) |
| What regulates the secretion of calcitonin | C Cell due to [Ca], Ca receptors, Glucocorticoids, Glucagon, GI hormones |
| Calcitonin affects tissue via what type of receptor | G protein coupled receptor |
| What is the role of calcitonin | In animals, calcitonin decreases osteoclast-mediated bone resorption. But not sure if this is the same in humans. May serve as a tumor marker because secreted by severl tumor types. |
| What class of hormone is Parathyroid hormone | Polypeptide |
| What cells synthesize parathyroid hormone | Chief cells synthesize it as a preprohormone that is cleaved to mature parathyroid hormone |
| Where is the active protion of parathyroid hormone | The N-terminal region (~14 aa) |
| What stimulates the secretion of parathyroid hormone | Absolute [Ca] and Rate of chanage of [Ca] |
| How does Ca regulate the secretion of parathyroid hormone | Ca binds a G protien receptor on chief cells and inhibits cAMP which stimulates phospholipase C causing an increase in [Ca] blocking the release of hormone |
| What does a decrease in [Ca] do to the secreation of parathyroid hormone | Results in less binding to the receptor and relief of inhibition on exocytosis of parathyroid hormone, so an increase in the synthesis of parathyroid hormone and release of parathyroid hormone, and proliferation of parathyroid cells |
| What are the effects of parathyoid hormone | 1. Efflux of calcium from bone 2. Decreased loss of calcium in urine 3. Enhanced absorption of calcium from the intestine 4. Overall, increased concentration of calcium in the blood |
| Parathyroid hormone stimulates renal synthesis of what | 1,25 hydroxyvitamin D |
| What converts 7-dehydrocholesterol to Cholecalciferal (vitamin D3) | Skin via UV light |
| What converts 25-hydroxycholecalciferal (25,OHD3) to 1,25 hydroxyvitamin D | Kidney 1 alpha-hydroxylase stimulated by parathyroid hormone |
| 1,25 hydroxyvitamine D does what | Stimulates Ca and phosphate absorption by small intestine, Enhances renal reabsorption of Ca, Inhibits synthesis of PTH |
| Where does parathyroid hormone bind in bone | Receptors on osteoblasts |
| What effect does parathyroid have on bone | Increases the production of macrophage colony-stimulating factor and RANk ligands which stimulates teh production of osteoclasts and increases teh activity of mature osteoclasts (RANK in the latter case) |
| What is a common cause of hyperparathyroidism secretion | Adenoma |
| What is a manifestation of hyperparathyroidism | Osteoporosis |
| Hypoparathyroidism can be due to | Autoimmune problems, damage (surgury) |
| What can hypoparathyroidism cause | Muscle weakness and cramps, Numbness and tingling in extremities especially fingers and toes |
Created by:
mhaynes
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