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EXCI360 midterm > Thyroid Metabolic Hormones > Flashcards

Thyroid Metabolic Hormones Flashcards

1
Q

thyroid gland 2 main hormones

A

T4 93%
T3 7%
also produces calcitonine

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2
Q

calcitonine

A

minor role in maintaining Ca2+ and phosphate

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3
Q

chronic lack of TH

A

decrease BMR to 40-50% below normal
will feel cold and gain weight possibly

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4
Q

chronic excess TH

A

increase BMR to 60-100% above normal
feel hot and lose bw possibly

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5
Q

iodine

A

chemical element
turn into ion iodide
have to consume iodiDe
only thyroid gland needs iodide in the body

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6
Q

iodide pump

A

actively transport the iodides from the blood into the thyroid gland
iodide trapping

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7
Q

iodide trapping

A

not very effective
20% of iodide in blood is taken by thyroid gland
rest is excreted by kidney

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8
Q

colloid

A

in follicles of the thyroid gland
mainly composed of glycoprotein called thyroglobulin

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9
Q

thyroglobulin

A

contains TH and secretes into follicular colloid to be stored
prehormone
contains 70 tyrosine amino acids
reservoir of TH hormones

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10
Q

formation of TH

A

peroxidase is needed to add 3-4 iodide molecules to 2 tyrosines

TH stored in body for 2-3 months so takes time to observe effects of deficiency

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11
Q

what happens to thyroglobulin once TH is synthesized

A

TH remains attached to it

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12
Q

how is T3 and T4 released from thyroid gland

A

proteinases digest thyroglobulin and releases the hormones
diffuse from the thyroid cells into the blood

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13
Q

what can cause iodide deficency

A

lack of deiodinase enzyme because can’t recycle iodide

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14
Q

how does T3 and T4 get transported to the tissues

A

combine with several plasma binding proteins :
thyroxine-binding globullin (mainly
Thyroxine-binding prealbumin
albumin

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15
Q

what is the rate of release of T3 and T4 to the tissues

A

T3: one day
T4: 6 days because plasma binding protein has higher affinity for T4

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16
Q

general effect of TH

A

cause nuclear transcription of genes for synthesizing large number of substances

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17
Q

what 4 substances are synthesized by TH

A

enzymes
structural proteins
transport proteins
other

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18
Q

what hormones binds the most to receptors

A

T3 (more than 90%)

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19
Q

once TH is attached to receptor, attach to DNA…

A

receptors activate and initiate transcription process
messenger RNA formed
new proteins formed by RNA translation on cytoplasmic ribosomes

20
Q

effects of TH on mitochondria

A

increase number of mitochondria
increase total membrane surface (size) of mitochondria
increase formation rate of ATP

21
Q

effects of TH on carbohydrate metabolism

A

increase metabolic enzymes
increase absorption rte of glucose from GI tract
increase uptake rate of glucose by cells
enhances glycolysis
enhances gluconeogenesis
increase insulin secretion, and uptake by tissues
decreases glycogen stores in the liver and skeletal m. glycogennolysis, more glucose enters circulation

22
Q

effects of TH of fat metabolism

A

increase fat catabolism, lipolysis in adipose tissue
increase FFA concentration in plasma
accelerate oxidation of FFA by cells
decrease cholesterol, phospholipids and tryglycerides
increase fat anabolism in the liver

23
Q

lack of TH, hypothyroidism

A

excessive fat deposition in liver
can cause arteriosclerosis due to accumulation of cholesterol

24
Q

effects of TH of protein metabolism

A

increase protein synthesis

25
Q

effects of hyprethyroidism on protein

A

increase proteolysis
weaken m. overtime

26
Q

effects of TH on vitamin metabolism

A

increase quantity of enzymes and need for vitamins
can cause relative vitamin deficiency unless increase intake

27
Q

effects of TH on the body (3)

A

increase transport rate of Na and K ions
increase heat production
cell membranes become leaky to Na ions

28
Q

effects of TH on growth

A

lack causes retarded growth rate in children
excessive causes rapid skeletal growth

29
Q

effects of TH onCV system

A

increase BF and CO because of rapid utilization of oxygen
increase HR
increase strength of heart beat
increase slightly BV because of vasodilation
increase arterial pressure

30
Q

effects of TH on respiration

A

increase rate and depth bc increased rate of metabolism and use for oxygen

31
Q

effects of TH on GI tract

A

increase secretion rate of digestive juices and motility of GI tract
Excess causes diarrhea
Lack causes constipation

32
Q

effects of TH on CNS

A

increase brain activity
excess causes anxiety, extreme worry and paranoia

33
Q

effects of TH on muscle function

A

muscle becomes weakened with excess TH because of excessive protein catabolism
lack causes muscles to become sluggish and slow relaxation after a contraction
excess causes muscle tremor because of increased reactivity of neural synapses in the are of the spinal cord that controls muscle tone

34
Q

summary of metabolic effects of TH

A
35
Q

regulation of TH secretions

A

hypothalamic hormone called TRH secreted by nerve endings in the median eminence of the hypothalamus

36
Q

mechanism controlling TH secretions

A

TRH transported to ant pituitary through hypothalamic-hypophysial portal vessel
TRH binds with receptor on pit cell membrane
activates second messenger
cells in ant. pit. produce and release TSH
TSH binds with receptor on basal membrane surface of thyroid cell

37
Q

TSH causes increased release of TH because of

A

proteolysis of thyroglobulin
activity of iodide pump
iodination of tyrosine for forming TH
size and number of thyroid cells

38
Q

control secretion of TSH by negative direct feedback

A

concentration level of TH feedback to ant. pit.

39
Q

control secretion of TSH by negative indirect feedback (5)

A

increased TH
increased metabolic function
increased heat
increased body temp
affects hypothalamus

40
Q

feedback diagram

A
41
Q

hyperthyroidism

A

thyroid gland increase 2 to 3 times normal size
increase number and size of cells
increased secretion rate
goiter

42
Q

hyperthyroidism causes

A

autoimmunity
antibodies bind to TSH receptors
thyroid adenoma

43
Q

symptoms and consequences of hyperthyroidism

A

high state of excitability
intolerance to heat
increased sweating
mild to extreme weight loss
different degrees of diarrhea
muscle weakness
nervousness
protrusion of eyeballs
extreme fatigue
inability to sleep
tremor of hands
other psychiatric disorders

44
Q

hypothyroidism cause

A

autoimmunity destroys gland
thyroid inflammation: secretion of TH stops or diminished
lack of iodine: prevents production of TH

45
Q

genetic abnormality affecting TH production

A

deficient iodide-trapping mechanism

46
Q

symptoms and consequences of hypothyroidism

A

fatigue
extreme somnolence
extreme muscular sluggishness
slow HR
decreased BV and CO
increased weight
constipation
mental slugishness
scaling of skin
edematous appearance
increase of blood cholesterol

47
Q

comparison of hyper and hypo

A

EXCI360 midterm (9 decks)

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