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Physio II > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

Gestational deficiency of thyroid hormone will lead to what?

A

Cretinism (congenital hypothyroidism)

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2
Q

What is the functional unit of the thyroid?

A

Follicular cell

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3
Q

What cells releases calcitonin?

A

Parafollicular cells

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4
Q

Where are thyroid hormones stored?

A

Colloid

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5
Q

What is the precursor of thyroid hormones?

A

thyroglobin

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6
Q

Increased colloid will be found with HYPERthryoid or HYPOthyroid?

A

HYPOthyroid

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7
Q

Is more iodide found in stored in the thyroid or in plasma?

A

Thyroid storage (100:1)

*Protects against iodide deficiency

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8
Q

Iodide uptakes happens on the basal or apical membrane?

A

Basal membrane

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9
Q

What symporter brings iodide into the cell?

A

2Na/I symporter (NIS)

*Facilitated by Na/K-ATPase

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10
Q

What opens the anotamin-1/I channel?

A

TSH binding to receptor

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11
Q

Will NIS be up or down regulated w/ low iodide diet?

A

Unregulated

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12
Q

Loss of negative feedback due to no T3/T4 will cause what?

A

↑ TSH activity = goiter

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13
Q

With hypothyroidism, will there be increased or decreased uptake of radioactive iodide tracer?

A

decreased

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14
Q

A mutation NIS will lead to a defect in what?

A

Iodide transport

SX: hypothyroidism, goiter, and ↓ uptake of radio-iodide

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15
Q

Production of a thyroid stimulating immunoglobulin will stimulate or block the release of T3/T4?

A

Stimulate

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16
Q

Production of a thyroid stimulating immunoglobulin will ultimately lead to what with regards to the thyroid gland?

A

Hypertrophy and hyperplasia => goiter

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17
Q

In what tissues is NIS independent of TSH? (3)

A
  1. Gastric mucosa
  2. Placenta
  3. Lactating mammary glands
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18
Q

What are the pharmacologic inhibitors of iodide uptake? (2)

A
  1. Perchlorate

2. Thiocyanate

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19
Q

What are the 5 steps of thyroid hormone synthesis?

A
  1. Uptakes (basal membrane)
  2. Oxidation (apical membrane)
  3. Organification (follicular lumen)
  4. Coupling of iodinated tyrosines (apical membranes)
  5. Secretion (basal-lateral membrane)
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20
Q

What transports iodine to the apical membrane for it to be oxidized?

A

Pendrin

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21
Q

Goiter in childhood with progressive hearing loss is what syndrome?

A

Pendrin Syndrome
(due to mutation in pendrin gene)

hypothyroidism

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22
Q

What blocks TPO?

A

Propylthiouracil (PTU)

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23
Q

What oxidizes iodide to iodine?

A

Thyroid peroxidase (TPO) w/ H202 as oxidizing agent

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24
Q

Where does oxidation of iodine occur?

A

Apical membrane

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25
Q

Where does organification of iodine occur?

A

Follicular lumen

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26
Q

Tyrosine residues w/ TG (glycoprotein) are iodinated via TPO to form what?

A

Monoiodinated tyrosine (MIT) and Diiodinated tyrosine (DIT)

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27
Q

What is the name of the effect that temporarily blocks thyroid hormone production when plasma iodide levels are high?

A

Wolff-Chaikoff effect

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28
Q

Propylthiouracil blocks TPO in what three stages of TH synthesis?

A

Oxidation
Organification
Coupling

29
Q

What couples MIT and DIT residues to form T3 and T4?

A

TPO

30
Q

MIT + DIT is T3 or T4?

A

T3

31
Q

DIT + DIT is T3 or T4?

A

T4

32
Q

Where is T3/T4 stored until stimulated by TSH?

A

In colloid w/ TG

33
Q

Where does coupling of iodinated tyrosines take place?

A

Apical membrane

34
Q

Where does secretion of TH take place?

A

Basal lateral membrane

35
Q

TSH stimulation leads to X induced endocytosis?

A

Megalin (folliculuar cells engulf colloid @ apical membrane)

36
Q

What two substances allow T3/T4 to diffuse into the blood?

A

Lysosomes

Proteases

37
Q

What enzymes deiodinates MIT and DIT allowing for free iodine to be recycled?

A

Intrathyroid deiodinase

38
Q

What thyroid hormones is most abundant in the blood?

A

T4&raquo_space;> T3, rT3

39
Q

What transports bring TH into peripheral cells

A

NaTCp
Na independent OATP
LAT
MCT

40
Q

Na independent OATP has a preference for T3 or T4?

A

T4

41
Q

MCT transporter has a preference for T3 or T4?

A

T3

42
Q

Mutations in what peripheral cell transporter is associated w/ psychomotor retardation and TH resistance?

A

MCT

43
Q

T4 will sequentially diodinate to T3 until levels are what in the cell?

A

T3/T4 levels are equal

44
Q

TH binds to the thyroid hormone receptor on the promotor region of DNA regulating transcription. This leads to what general effects?

A

Genomic effect

45
Q

Does the thyroid hormone receptor have greater affinity for T3 or T4?

A

T3 (making it more potent)

46
Q

Do genomic or non-genomic effects of thyroid hormone exert more rapid effects?

A

Non-genomic (do not require gene transcription) => rapid effects on ion fluxes (T3 > T4)

47
Q

Stimulation of
1. Ca-ATPase (SR - heart and skeletal muscles)
2. Na and K channel activation
3. L-type Ca channel
4. Na/H antiporter in muscle
5. Na/K-ATPase
6. Amino acid uptake (cell proliferation)
are genomic or non-genomic effects of TH?

A

Non-genomic

48
Q

Calorigenic action of TH occurs in all tissues except? (3)

A

Brain
Gonads
Spleen

49
Q

↑ O2 consumption → ↑ basal metabolic rate (BMR) and; ↑ body temp is regulated by TH stimulating what type of pump?

A

↑ Na/K-ATPase pump

50
Q

What effects does TH have on CV system? (5)

A

↑ CO
↑ ventilation
↑ chronotropic
↑ inotropic

↓ vascular resistance

51
Q

Is T3 or T4 responsible for CV effects of TH?

A

T3

52
Q

TH ↑ glucose absorption, gluconeogenesis, glycogenolysis. What impact does this have on serum glucose? Increase, decreased or maintain normal?

A

Normal serum glucose

53
Q

Lipolysis and protein catabolism are two effects of TH. Their byproducts (glycerol and amino acids) are essential for what process?

A

Gluconeogenesis

54
Q

TH stimulates protein synthesis/breakdown.

T or F: This results in a net degradation of tissue protein => neg nitrogen balance.

A

TRUE

55
Q

What effect does TH have on B-adrenergic receptors (SNS) in cardiac/ skeletal muscles and adipocytes?

A

Increased synthesis => up regulation => more sensitive to SNS effect

56
Q

How does TH impact fetal development? (4)

A
  1. Required for normal growth
  2. Synergistic w/ GH → bone formation
  3. Protein synthesis (anabolic)
  4. CNS maturation, axonal growth, myelination

*Dysfunction/ low levels at birth can be reversed w/ early tx

57
Q

What hormones regulate the secretion of TH? (5)

A
  1. TRH
  2. Dopamine
  3. Somatostatin
  4. TSH
  5. Peripheral T3/T4
58
Q

T3/T4 have a positive or negative feedback effect?

A

Negative. Will down regulate TSH receptors on thyrotrophs

59
Q

Hepatic sulfation and glucoronide conjugation result in what with regards to TH?

A

↑ solubility and biliary excretion

60
Q

Does free T3/T3 generated from T4 or T4 have a greater effect on regulating secretion of TH?

A

T3/ T3 generated from T4

61
Q

Do you have a faster or slower BMR with hypothyroidism?

A

Slower

Hyperthyroidism w/ fast BMR

62
Q

Mutation to NIS gene, Hashimoto’s, low iodide diet and Thyroiditis are associated w/ Hyper or Hypothyroidism?

A

Hypothyroidism

63
Q

T or F: Goiter can be seen with both hyper and hypothyroidism?

A

TRUE

64
Q

Propylthiouricil (PTU), removal of part or entire thyroid gland, radioactive I and 𝛽-adrenergic antagonist are tx for hyper or hypothyroidism?

A

HYPERthyroidism

65
Q

Hyperprolactimemia, cold intolerance, cramp and aches are associated w/ HYPER or HYPOthyroidism?

A

HYPOthyroidism

66
Q

High glycoprotein TG levels, increased uptake of radioactive I tracer, heat intolerance, and muscle weakness are associated w/ HYPER or HYPOthyroidism?

A

HYPERthyroidism

67
Q

Graves disease (immunoglobulin to TSH receptor) is associated w/ HYPER or HYPOthyroidism?

A

HYPERthyroidism

68
Q

Pendrin syndrome (hearing loss and low iodide) is associated w/ HYPER or HYPOthyroidism?

A

HYPOthyroidism

Physio II (14 decks)

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