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Physio Exam 5

Thyroid and Parathyroid

QuestionAnswer
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