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28 Cards in this Set

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