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24 Cards in this Set

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  • Back
Thyroglobulin
primary component of colloid in thyroid follicles
T3 and T4 stored here until release from gland
tyrosyl residues in TGB are sites of
T3 and T4 synthesis
T3 vs. T4
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
thyroid binding globulin binds 60-75% of
T3/T4
Thyroxine binding prealbumin does not bind
T3
TBG increased by
pregnancy
neonates
estrogens
oral contraceptives
TBG decreased by
diphenylhydantoin
androgens
anabolic steroids
large dose glucocorticoids
Thyroid hormone metabolism
85-90% deiodination in all peripheral tissues
15% conjugation (mostly by liver)
TRH
made in hypothalamus and stimulates release of TSH
TRH release
increased by onset of sleep, NE, and cold in infants and children
decreased by sleep, stress, dopamine, and somatostatin
TSH effects on thyroid
increased colloid production
increased TGB turnover
increased iodine uptake
increase T3 and T4 production and secretion
inhibitors of TSH release
T3/T4
somatostatin
dopamine
stress
exercise
fasting
aging
iodide excess
Wolf-Chaikoff effect
decreased TSH secretion due to iodide excess
propranolol
counters catecholamine effects
in metabolism, T3/T4 increases
oxygen use
protein synthesis
carb, fat, and cholesterol turnover
vitamin metabolism
beta-carotene --> vitamin A requires
T3/T4
poor conversion of B-carotene --> vitamin A seen in
hypothyroidism
increase BC in blood
skin shows yellowish tint
T3/T4 required in fetus for
normal brain tissue growth
normal neurons
myelination
untreated T3/T4 deficiency leads to
incomplete brain growth in utero
permanent mental retardation if not treated by 3 months post partum
T3/4 MOA
only AA-derived hormone with a nuclear site of action
goiter formation
due to iodine def. or goitrogens

TSH stimulates thyroid causing enlargement
Grave's disease
hyperthyroid condition
exophthalmos seen
caused by thyroid stimulating immunoglobulins
plummer's disease
somatic point mutation in TSH receptor gene causing activation without TSH
beta-adrenergic hypersensitivity
seen in hyperthyroidism

nervousness
anxiety
tachycardia
insomnia