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ANSC 3080 > Midterm 2 - Importance of Thyroid Hormones > Flashcards

Midterm 2 - Importance of Thyroid Hormones Flashcards

1
Q

where is the thyroid gland located

A

both side of the trachea, below the larynx

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2
Q

what are the 2 lobes of the thyroid gland bridged by

A

isthmus

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3
Q

what are characteristic of the thyroid gland

A

heavily vascularized
heaviest of pure endocrine glands

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4
Q

what is the thyroid gland composed of

A

numerous follicles

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5
Q

what are follicles in the thyroid gland

A

a single layer of epithelial cells that release thyroid hormones
lumen filled with protein rich fluid (colloid)

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6
Q

what occurs between follicles in the thyroid gland

A

parafollicular cells (C-cells) secrete calcitonin

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7
Q

how much of circulating thyroid hormones does TBG bind to

A

70-80% - remaining binds to other albumins

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8
Q

what percentage of T3 and T4 are free in blood

A

0.03%

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9
Q

why is there several days of hormone available bound to TBG

A

only 0.03% free in blood and diffuse to tissues - only free hormone is active

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10
Q

what are free and bound forms in

A

equilibrium

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11
Q

what cells do thyroid hormones act on

A

all cells of the body

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12
Q

what do thyroid hormones act on all cells to do

A

increase basal metabolic rate by increasing heat production and O2 consumption

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13
Q

where does O2 consumption not increase due to thyroid hormones

A

brain
gonads
spleen

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14
Q

what do TH stimulate during development

A

GH

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15
Q

what can a TH deficiency lead to

A

dwarfism - TH is important for bone and tissue growth

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16
Q

when are TH critical for normal maturation of brain function

A

during the last phase of foetal development and early stage after birth

17
Q

what can a lack of TH lead to

A

cretinism

18
Q

what do TH increase

A

the number of adrenalin/noreadrenalin receptors –> boost sensitivity to SNS

19
Q

what are TH essential for

A

gonadal normal function

20
Q

what does a lack of TH in gonad lead to

A

reduced sperm produciton
irregular cycles

21
Q

how does TH effect reflexes

A

increases nerve conduction velocity –> faster reflexes

22
Q

what is hypothyroidism mainly due to in humans

A

iodine deficiency

23
Q

what can hypothyroidism result in

A

reduced growth and mental retardation

24
Q

what is hypothyroidism mainly due to in dogs

A

autoimmune disorders that destroy follicular cells = primary hypothyroidism

25
Q

what do lab tests show in dogs with hypothyroidism

A

low T4 and T3 with high TSH

26
Q

what is secondary hypothyroidism due to

A

low secretion of TSH, mainly due to injury to pituitary or hypothalamus

27
Q

what cell types are affected by hypothyroidism

A

most

28
Q

symptoms of hypothyroidism

A

reduced heat production and tolerance to cold
sluggish animal, not feeding but gaining weight
impaired reproduction
constipation

29
Q

treatment for hypothyroidism

A

thyroxine for the rest of life

30
Q

what is a goiter

A

enlarged thyroid gland

31
Q

what are causes of goiter

A

iodine deficiency
tumor and inflammation
lack of thyroid hormones increases TRH and TSH release (lack of feedback) which stimulates multiplication (hyperplasia) and volume (hypertrophy) of follicular cells

32
Q

what area of animal are gaiters more frequent in

A

inland - coastal air, vegetation, and marine organisms are a good source of iodine

33
Q

hyperthyroidism

A

over-production of thyroid hormones

34
Q

what animal is hyperthyroidism frequent in

A

cats - unknown cause

35
Q

what does hyperthyroidism target

A

many target organs

36
Q

symptoms of hyperthyroidism

A

big appetite associated with weight loss
excitable and nervous
increased heart rate, respiration and digestive passage

37
Q

treatment of hyperthyroidism

A

surgery, radioactive I2 to destroy follicular cells

38
Q

what is Tgb

A

a glycoprotein with over 120 tyrosine residues

ANSC 3080 (21 decks)

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