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24 Cards in this Set
- Front
- Back
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Thyroglobulin
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primary component of colloid in thyroid follicles
T3 and T4 stored here until release from gland |
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tyrosyl residues in TGB are sites of
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T3 and T4 synthesis
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T3 vs. T4
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T3 is 4x more potent than T4
T4 is 3-4x more abundant in thyroid and also released in 4:1 ratio most T3 results from deiodination of T4 |
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thyroid binding globulin binds 60-75% of
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T3/T4
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Thyroxine binding prealbumin does not bind
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T3
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TBG increased by
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pregnancy
neonates estrogens oral contraceptives |
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TBG decreased by
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diphenylhydantoin
androgens anabolic steroids large dose glucocorticoids |
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Thyroid hormone metabolism
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85-90% deiodination in all peripheral tissues
15% conjugation (mostly by liver) |
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TRH
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made in hypothalamus and stimulates release of TSH
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TRH release
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increased by onset of sleep, NE, and cold in infants and children
decreased by sleep, stress, dopamine, and somatostatin |
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TSH effects on thyroid
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increased colloid production
increased TGB turnover increased iodine uptake increase T3 and T4 production and secretion |
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inhibitors of TSH release
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T3/T4
somatostatin dopamine stress exercise fasting aging iodide excess |
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Wolf-Chaikoff effect
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decreased TSH secretion due to iodide excess
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propranolol
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counters catecholamine effects
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in metabolism, T3/T4 increases
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oxygen use
protein synthesis carb, fat, and cholesterol turnover vitamin metabolism |
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beta-carotene --> vitamin A requires
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T3/T4
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poor conversion of B-carotene --> vitamin A seen in
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hypothyroidism
increase BC in blood skin shows yellowish tint |
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T3/T4 required in fetus for
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normal brain tissue growth
normal neurons myelination |
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untreated T3/T4 deficiency leads to
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incomplete brain growth in utero
permanent mental retardation if not treated by 3 months post partum |
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T3/4 MOA
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only AA-derived hormone with a nuclear site of action
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goiter formation
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due to iodine def. or goitrogens
TSH stimulates thyroid causing enlargement |
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Grave's disease
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hyperthyroid condition
exophthalmos seen caused by thyroid stimulating immunoglobulins |
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plummer's disease
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somatic point mutation in TSH receptor gene causing activation without TSH
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beta-adrenergic hypersensitivity
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seen in hyperthyroidism
nervousness anxiety tachycardia insomnia |
