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z:Physl 210A/B > Endo Lec 4 > Flashcards

Endo Lec 4 Flashcards

1
Q

thyroid gland (def.)

A

bi-lobed gland in front of trachea

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2
Q

thyroid gland made of ..

A

-follicles and parafollicular cells

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3
Q

thyroid gland follicles are made of

A

–follicular cells lining the surface and a cavity filled with colloid (gelatinous material)

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4
Q

resting vs. actively secreting follicle

A

actively secreting follicle increases in size

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5
Q

parafollicular cells secrete

A

calcitonin

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6
Q

thyroid follicles secrete

A

T3 & T4

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7
Q

list of thyroid hormones

A
  • T3
  • T4
  • calcitonin
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8
Q

thyroid hormones synthesized from

A

tyrosine and I2

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9
Q

intermediates of thyroid hormones synthesis

A
  • Monoiodotyrosine (MIT)

- Di-iodotyrosine (DIT)

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10
Q

active end products of thyroid hormones synthesis

A
  • Tri-iodothyronine (T3)

- Tetra-iodothyronine or thyroxine (T4)

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11
Q

synthesis of thyroid hormones

A
  1. iodide is cotransported with Na+ into follicle cell and I- diffuses into colloid
  2. Iodide is oxidized and attached to tyrosines in thyroglobulin (TG)
  3. formation of T3 + T4 attached to TG
  4. endocytosis of TG containing T3,T4 molecules into follicle cell
  5. lysosomal enzymes release T3/T4 from TG
  6. T3/T4 secretion out of follicle cell
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12
Q

TG (thyroglobulin) is synthesized in ….and secreted to…

A
  • follicle cell

- secreted to colloid

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13
Q

NIS stands for

A

sodium-iodide symporter (active transport)

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14
Q

Thyroid follicular cells (also called…)

A

thyroid epithelial cells or thyrocytes

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15
Q

thyroglobulin (TG)–def.

A

glycoprotein that contains tyrosine

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16
Q

iodination of tyrosine form..

A

iodotyrosines (MIT & DIT)

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17
Q

Tyr + 1 iodine =

A

MIT

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18
Q

Tyr + 2 iodine=

A

DIT

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19
Q

MIT stands for

A

-Monoiodotyrosine

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20
Q

DIT stands for

A

–Di-iodotyrosine

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21
Q

DIT + MIT=

A

tri-iodothyronine (T3)

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22
Q

DIT + DIT=

A

`tetra-iodothyronine/thyroxine (T4)

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23
Q

T3 stands for…(1 name)

A

tri-iodothyronine

24
Q

T4 stands for.. (2 names)

A
  • tetra-iodothyronine

- thyroxine

25
Q

T4 storage __ T3 storage in colloid

A

> (greater)

26
Q

T4 secretion __ T3 secretion in blood

A

> (greater)

27
Q

during thyroid hormones synthesis, there is recycling of …

A

I- and amino acids

28
Q

T3 & T4 are transported in blood mainly bound to…

A

thyroid binding protein (TBP)

29
Q

T3 amount free in blood (%)

A

0.3%

30
Q

T4 amount free in blood (%)

A

0.03%

31
Q

which is more potent (T3/T4)?

A

T3 is 3-8x more potent than T4

32
Q

which is prohormone/biologically active form (T3 & T4)?

A

prohormone: T4

biologically active form: T3

33
Q

… is converted to … in

A
  • T4
  • T3
  • peripheral cells and liver
34
Q

which is produced more %(T4 OR T3)

A

T4 (90%) vs T3 (10%)

35
Q

T3 binds to ..

A

nuclear receptors

36
Q

control of thyroid hormone secretion

A

↑ TRH secrection
↑ TSH secerection
↑ T3/T4 secrection

37
Q

↑ T3/T4 (feedback)

A

(-) TSH secretion

(-) TRH secretion

38
Q

↑ T3/T4 (feedback)

A

(-) TSH secretion

(-) TRH secretion

39
Q

physiological actions of T3/T4

A
  • act on most tissues (change in transcription and translation process)
  • increase metabolism
  • required for growth and development
40
Q

7 metabolic effects of T3

A
  1. Catabolism/anabolism ↑
  2. ↑ BMR (basal metabolic rate), ↑O2 consumption ↑heat
  3. ↑ carbohydrate absorption/use
  4. ↑ protein breakdown (muscle)
  5. ↑ fat breakdown
  6. ↑ cholesterol metabolism
  7. ↑ serum cholesterol (LDL)
41
Q

5 growth + development effects of T3

A
  1. Act as “tissue growth factors”
  2. Small amounts stimulate protein synthesis
  3. Increase GH/IGF-1 production
  4. Essential for CNS maturation during fetal
    stage
  5. Maternal hypothyroidism results in poor
    fetal CNS development and mental
    developmental disability
42
Q

3 permissive effects of T3

A
  1. Cardiovascular system (beta adrenergic
    receptors): increased HR and contractility,
    increased blood pressure
  2. Potentiation of Sympathetic Nervous System
    (beta-2 adrenergic receptors)
  3. Reproductive system: necessary for normal
    function and fertility
43
Q

graves’ disease def. + problem

A
  • is the over activity of gland
  • autoimmune disorder
  • antibody to TSH receptor stimulates thyroid hormone production
44
Q

graves’ disease associated with

A
  • increased BMR (basal metabolic rate)
  • exophthalmos (bulging or protruding eyeballs)
  • goitre
45
Q

hashimoto’s thyroiditis def. + problem

A
  • is the underactivity of gland
  • autoimmune disorder
  • TPO (thyroid peroxidase) antibody destroy thyroid gland to block hormone synthesis
46
Q

hashimoto’s thyroiditis is the most common

A

autoimmune cause of hypothyroidism

47
Q

hashimoto’s thyroiditis associated with

A
  • myxedema (adult-onset) = severely advanced hypothyroidism, swollen puffy skin
  • goitre
  • cretinism (in children only)= underactive thyroid function at birth
48
Q

11 hypothyroidism symptoms

A
  1. Lethargy
  2. Weight gain
  3. Cold intolerance
  4. Constipation
  5. Nausea / low appetite
  6. Menorrhagia (heavy periods)
  7. edema
  8. Shortness of breath
  9. “myxedema madness”
  10. Dry skin
  11. Brittle hair and nails
49
Q

goitre can happen for both … cases

A

hypothyroid and hyperthyroid

50
Q

goitre formation (hyperthyroidism)

A 
thyroid gland enlarges
↑ T3/T4
strong negative feedback 
↓ TSH
↓ TRH
51
Q

goitre formation (hypothyroidism)

A 
↓ T3/T4
(+) ↑TRH, ↑TSH
thyroid gland enlarges
no iodine
T3/T4 remain low
52
Q

TSH measurement is the ….. for thyroid function

A

best single screening test

53
Q

Changes in TSH occur often before measurable changes

A

in T4 or T3 are present

54
Q

TSH reflects the true state

A

of Free T4, Free T3

55
Q

Iodine deficiency in the diet is the most common cause of

A

– Hypothyroidism
– Goitre
– Developmental/intellectual disability
– Preventable brain damage

56
Q

µg iodine/day only needed?

A

150 µg iodine/day

z:Physl 210A/B (28 decks)

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