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Thyroid and Parathyroid

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Question
Answer
What cells are responsible for the production of the components of colloid   Epithelial cells  
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What are two important components of colloid   Thyroid hormone and thyroglobulin  
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Where are prafollicular (C cells) located in the thyroid   The interfollicular space and/or wall of the follicles  
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What do the parafollicular (C cells) produce   Calcitonin  
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What is colloid   The storage form of thyroid hormones  
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What stimulates the synthesis of thyroid hormone   Thyroid stimulating hormone released from the anterior pituitary glan d  
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What is thyroid hormone built from   Tyrosine residues of thyroglobulin that have been iodinated  
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If you add one iodine to the thyrosine residue you get   Monotyrosine (MIT)  
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If you add two idone groups to the thyrosine residue you get   Diiodotyrosine (DIT)  
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Are monotyrosine and diiodotyrosine active or inactive   Inactive  
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The coupling of a monotyrosine and a diiodotyrosine yields a   Triiodothyronine (T3)  
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What is the most active thyroid hormone   Triiodothyronine (T3)  
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What thyroid hormone is has the smallest concentration released   Triiodothyronine (T3)  
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The coupling of two diiodotyrosine yields a   Thyroxine (T4)  
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What is the primary secretory product of the thyroid gland   Thyroxine (T4)  
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What enzyme catalyzes the addition of iodine to the tyrosine residues of thyroglobulin to form DIT and MIT   Thyroperoxidase (TPO)  
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What enyzme provides the H2O2 needed for the addition of iodine to the tyrosine residues of   Thyroid oxidase  
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What catalzses the coupling of DIT and/or MIT to form T4 or T3   Thyroid oxidase  
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What enzyme catalyzes the addition of iodine to the tyrosine residues of thyroglobulin to form DIT and MIT   Thyroperoxidase (TPO)  
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What enyzme provides the H2O2 needed for the addition of iodine to the tyrosine residues of   Thyroid oxidase  
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What catalzses the coupling of DIT and/or MIT to form T4 or T3   Thyroid oxidase  
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How many types of thyroid hormone deiodinases are there   Three Types 1-3  
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What reaction does type 1 thyroid hormone deiodinase catalyze   T4 --> T3  
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Where is type 1 thyroid hormone deiodinase located   Liver, Kidney, Thyroid  
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What reaction does type 2 thyroid hormone deiodinase catalyze   T4 --> T3  
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Where is type 2 thyroid hormone deiodinase located   Brain, BAT, pituitary, pineal, cardia and skeletal muscle, placenta  
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What stimulates the synthesis and secretion of thyroid hormone   Thyroid stimulating hormone  
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What is responsible for bringing iodide into the cell   NIS: sodium/iodide symporter  
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What protein does iodide leave the cell thru and enter the colloid   Pendrin  
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The endocytosis of colloid is stimulated by what   The biding of thyroid stimulating hormone to its receptor  
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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  
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What reaction does type 3 thyroid hormone deiodinase catalyze   T3 --> T2  
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Where is type 3 thyroid hormone deiodinase located   Brain, skin, placenta  
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What are the proteins that T3 and T4 bind for transport in order of decreasing affinity   Thyroxine binding globule > Transthyretin > Albumin  
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T3 and T4 bind what kind of receptor   Intracellular  
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T3 binds what nuclear receptor   Thyroid hormone receptor (TR) bound as a heterodimer with Retinoid X receptor  
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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  
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Why are T3 and T4 bound to protiens in circulation   To increase the half-life  
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What are the major effects of thyroid hormone   1. Normal growth and metabolism 2. Overall oxygen utilization 3. Stimulation or inhibition of gene expression  
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What stimulates the release of thyroid hormone   Thyroid Stimulating hormone  
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What inhibits the release of thyroid hormone   T4 and T3  
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Hyperthyroidism can be caused by   Grave's Disease  
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What is Grave's disease   An autoimmune disorder in which the TSH receptor antibody stimulates the thyroid gland  
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Hypothyroidism is caused by what   Hashimoto's disease, Damage (radiation post-op), Thyroiditis, Drugs (lithium)  
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What is Hasimoto's disease   An autoimmune disorder in which there are antibodies against the thyroid cells  
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Hyperthyroidism is also called   Thyrotoxicosis  
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What class of hormone is Calcitonin   Polypeptide  
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What cells produce Calcitonin   Parafollicular (C cells)  
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What other product besided calcitonin can be expressed due to alternate splicing   Calcitonin gene related peptide (CGRP)  
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What regulates the secretion of calcitonin   C Cell due to [Ca], Ca receptors, Glucocorticoids, Glucagon, GI hormones  
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Calcitonin affects tissue via what type of receptor   G protein coupled receptor  
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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.  
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What class of hormone is Parathyroid hormone   Polypeptide  
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What cells synthesize parathyroid hormone   Chief cells synthesize it as a preprohormone that is cleaved to mature parathyroid hormone  
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Where is the active protion of parathyroid hormone   The N-terminal region (~14 aa)  
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What stimulates the secretion of parathyroid hormone   Absolute [Ca] and Rate of chanage of [Ca]  
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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  
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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  
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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  
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Parathyroid hormone stimulates renal synthesis of what   1,25 hydroxyvitamin D  
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What converts 7-dehydrocholesterol to Cholecalciferal (vitamin D3)   Skin via UV light  
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What converts 25-hydroxycholecalciferal (25,OHD3) to 1,25 hydroxyvitamin D   Kidney 1 alpha-hydroxylase stimulated by parathyroid hormone  
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1,25 hydroxyvitamine D does what   Stimulates Ca and phosphate absorption by small intestine, Enhances renal reabsorption of Ca, Inhibits synthesis of PTH  
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Where does parathyroid hormone bind in bone   Receptors on osteoblasts  
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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)  
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What is a common cause of hyperparathyroidism secretion   Adenoma  
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What is a manifestation of hyperparathyroidism   Osteoporosis  
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Hypoparathyroidism can be due to   Autoimmune problems, damage (surgury)  
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What can hypoparathyroidism cause   Muscle weakness and cramps, Numbness and tingling in extremities especially fingers and toes  
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