PHGY 210 Lecture Notes - Lecture 3: Cell Nucleus, Insulin-Like Growth Factor 1, Iodine Deficiency

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20 Jul 2016
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TSH. TSH interacts with specific receptors located on follicular cells, leading to increased production
of T4 and T3 %
o!TSH works through a g protein coupling process- thyroid hormone levels t3 and t4 go up and neg
feedback occurs%
!Iodine deficiency- you cannot synthesize adequate levels- neg feedback loop breaks, so the hypo and
pituitary overwork and extreme levels of TSH are produced, which bind to the receptors on thyroid and it
tries to produce the thyroid hormone. So the thyroid grows in size and a goiter is formed. This is a nontoxic
goiter!! Because the thyroid is still not producing toxic amts of hormone%
o!Decreased I2 = decreased synthesis of thyroid hormones and t3 and t3 in circulation decrease. Release
of TSH increased! Goiter %
!Summary of the effects of thyroid hormones%
o!Stimulation of calorigenesis in most cells%
!Increase in cardiac output: rate and strength of cardiac contractions%
!Increase in oxygenation of blood%
!Increase rate of breathine; increase number of red blood cells in the circulation%
o!Effects on carb metabolism%
!Promost glycogen formation in the liver; increase glucose uptake into adipose and muscle%
o!Effects on lipid turnover%
!Increased lipid synthesis, mobilization, and oxidation%
o!Effects on protein metabolism%
!Stimulate protein synthesis%
o!Promote normal growth%
!Promote neural branching and myelinization of nerves%
!Stimulate growth GH secretion, promote bone growth, promote IGF-1 production by the
liver%
!Promote development and maturation of the nervous system%
!Effects of thyroid on metabolic rate %
o!Increased calorigenesis or basic metabolic rate BMR%
!BMR- the rate at which the organism burns up its stores of fuel to produce energy in the
form of heat calories. Both t4 and t3 increase BMR. Thys, T4 and t3 increase the
breakdown of carbs, lipids, and proteins. Increases in metabolic rate increases the need for
o2%
o!Effect of thyroid hormones on growth%
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