thyroid hormones - lecture

Question 1

thyoidine

Answer 1

taken up into thyroid gland where its used to synthesize thyroxine (T4)

Question 2

cells that have thyroid hormone receptors

Answer 2

everything except for RBCs

Question 3

why is T3 more reactive than T4/

Answer 3

affinity of receptor for t3 much higher

Question 4

cretinism

Answer 4

child born without thyroid gland

mental retardation and dwarfism

Question 5

myxedema

Answer 5

mucopolysaccharides results in fluid accumulation under skin
remove thyroid and get disorder
weakness
dry skin
lethargy
sensation of cold
slow speech
edema of eyelids
cold skin
reduced sweating
plus others

Question 6

symptoms of thyrotoxicosis/graves’ disease

Answer 6

nervousness
increased sweating
intolerance to heat
palpitations
fatigue
weight loss
tachycardia
dyspnea
weakness
increased appetite
eye complaints

Question 7

symptoms of graves disease

Answer 7

thyrotoxicosis
goiter
edema of eyes = exophthalmos

Question 8

metabolic effects of TH

Answer 8

regulating:

1: basal metabolic rate and heat production
2: water and ion transport
3: calcium and phosphorus metabolism
4: cholesterol and fat metabolism - stimulates enzyme that breaks cholesterol down
5: nitrogen (urea and creatine) metabolism

Question 9

insufficient TH during development results in:

Answer 9

mental retardation
very limited growth
ataxia
spastic muscles
deafness
infertility 

none of this is reversible unless TH supplied during development

Question 10

neurological cretin

Answer 10

mother lacks iodine
T4 very low
will make t3 instead so will be euthyroid
but fetus needs T4 cause it crosses placenta more easily and gets into brain more easily than T3

Question 11

direct response genes

Answer 11

ones that have thyroid response elements
number of genes in CNS development, malic enzyme and alpha and beta myosin heavy chain genes, TSH pteta and alpha geins, myelin associated protein genes

Question 12

thyroid hormone receptors

Answer 12

alpha1 adn beta b1 adn b2 can bind to T3 but alpha 2 can’t

KO mice can live without all of them, but aren’t happy

Question 13

iodine and TH regulation

Answer 13

excess dietary iodine suppresses synthesis and release of hormones independent of TSH

Question 14

pathological thyroid regulatiors

Answer 14

tyroid stimulating immunoglobulins
TSH binding inhibiting immunoglobulins
human chorionic gonadotropin (hCG)

Question 15

TRH

Answer 15

synthesized in anterior hypothalamus
stored in median eminence
also found in other parts of the brain
there are TREs on alpha and beta TSH genes

Question 16

activation and inactivation of Th

Answer 16

activate by converting T4 to T3 by 5’-deiodinases

T4 to inactive rT3 by 5-deiodinases

Question 17

D1

Answer 17

generates T3 from T4 to export to plasma to maintain plasma levels
in liver, kidney, thyroid

Question 18

D2

Answer 18

in brain, pituitary, brown fat

generates T3 from T4, primarily for local use

Question 19

D3

Answer 19

in brain, uterus, placenta

protects tissues, especially developing brain, from excess T3

Question 20

5’-deiodinase

Answer 20

converts T4 to T3