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28 Cards in this Set
- Front
- Back
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What hormone stimulates the thyroid?
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TSH
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What 3 hormones does the thyroid secrete
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Triiodothyronine (T3) and Thyroxine (T4) and Calcitonin
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Which thyroid hormone is secreted most?
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Thyroxine (T4)
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Which thyroid hormone is more potent?
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Triiodothyronine (T3) is 4x more potent than thyroxine but it has a shorter half-life
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What is the major component of the colloid that fills the thyroid gland?
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Thryroglobulin, which contains thryoid hormones as part of its structure
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What effect does calcitonin have on calcium?
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Decreases calcium concentration, which is the opposite effect of PTH--it increases calcium concentration
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What structural characteristic allows T3 and T4 to come out of the colloid droplet to be secreted?
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They have 2 tyrosine rings
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What is the simplest way to stop TRH from secreting TSH?
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Regulation of the receptors
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What stimulates calcium secretion?
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Increased plasma Ca2+ concentrations
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What effect does T3/T4 have on metabolic processes?
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Increases metabolic processes
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What is the active form of T3
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3,5,3'
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What is the inactive form of T3
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rT3=3,3',5'
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What enzyme allows iodination and coupling of thyroglobulin precursor (TG)?
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Peroxidase
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This inflammatory disease is characterized by an initial increase in production of thyroid hormone followed by a decrease in the secretion of the hormone
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Hashimoto's
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Deficiency leads to hypothyroidism and possible goiter.
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Iodine deficiency
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Excessive iodine in blood can lead to decreased uptake b/c it decreases organic binding within the thryroid gland. What is this autoregulatory effect called?
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Wolff-Chaikoff effect
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If T3 is bound to a receptor, what happens?
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mRNA transcription is turned on and specific protein translation is induced
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This hormone works through a cell surface receptor mechanism with Gs stimulating adenylate cycleas, increasing cytosolic levels of cAMP
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TSH
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TRH works through phosphatidyl inositol, DAG, Protein kinase C mechanism, which utilizes which G protein mechanism?
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Gq
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What can desensitize the pituitary thyrotropes to the effects of TRH?
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T3
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What is the primary peripheral pathway T4 to T3 that is predominately found in the liver, kidney, and thyroid?
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Deiodinase I
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What degradation pathway is found in brown adipose, fat, brain, pituitary, thyroid, placenta, and skeletal and cardiac muscle.
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Deiodinase II
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This degradation path decreases direct flow of T3 from mother to fetus.
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Deiodinase III
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This disease characterized by exophthlamous, patient sweating, increased T3/T4 and decreased TSH
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Graves Disease
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This disease characterized by hypothyroid, and a tired, weak pt
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Myxedema
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What cells secrete calcitonin?
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Parafollicular cells
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What are the 2 ways calcitonin reduces plasma calcium?
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1. Decreases the bone absorptive activity of osteoclasts--shifting balance in favor of calcium deposition in bone 2. Decreases the formation of new osteoblasts. Thus, long-term affect is to reduce both types of activity. Reduction of plasma calcium is mainly transient--a few hrs to days
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Effect of calcitonin on plasma calcium levels in adults is weak b/c:
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1. Reduction of calcium stimulates PTH secretion 2. Daily absorption and deposition amts are small
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