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Physio II > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

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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
Where does organification of iodine occur?
Follicular lumen
26
Tyrosine residues w/ TG (glycoprotein) are iodinated via TPO to form what?
Monoiodinated tyrosine (MIT) and Diiodinated tyrosine (DIT)
27
What is the name of the effect that temporarily blocks thyroid hormone production when plasma iodide levels are high?
Wolff-Chaikoff effect
28
Propylthiouracil blocks TPO in what three stages of TH synthesis?
Oxidation Organification Coupling
29
What couples MIT and DIT residues to form T3 and T4?
TPO
30
MIT + DIT is T3 or T4?
T3
31
DIT + DIT is T3 or T4?
T4
32
Where is T3/T4 stored until stimulated by TSH?
In colloid w/ TG
33
Where does coupling of iodinated tyrosines take place?
Apical membrane
34
Where does secretion of TH take place?
Basal lateral membrane
35
TSH stimulation leads to X induced endocytosis?
Megalin (folliculuar cells engulf colloid @ apical membrane)
36
What two substances allow T3/T4 to diffuse into the blood?
Lysosomes | Proteases
37
What enzymes deiodinates MIT and DIT allowing for free iodine to be recycled?
Intrathyroid deiodinase
38
What thyroid hormones is most abundant in the blood?
T4 >>> T3, rT3
39
What transports bring TH into peripheral cells
NaTCp Na independent OATP LAT MCT
40
Na independent OATP has a preference for T3 or T4?
T4
41
MCT transporter has a preference for T3 or T4?
T3
42
Mutations in what peripheral cell transporter is associated w/ psychomotor retardation and TH resistance?
MCT
43
T4 will sequentially diodinate to T3 until levels are what in the cell?
T3/T4 levels are equal
44
TH binds to the thyroid hormone receptor on the promotor region of DNA regulating transcription. This leads to what general effects?
Genomic effect
45
Does the thyroid hormone receptor have greater affinity for T3 or T4?
T3 (making it more potent)
46
Do genomic or non-genomic effects of thyroid hormone exert more rapid effects?
Non-genomic (do not require gene transcription) => rapid effects on ion fluxes (T3 > T4)
47
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?
Non-genomic
48
Calorigenic action of TH occurs in all tissues except? (3)
Brain Gonads Spleen
49
↑ O2 consumption → ↑ basal metabolic rate (BMR) and; ↑ body temp is regulated by TH stimulating what type of pump?
↑ Na/K-ATPase pump
50
What effects does TH have on CV system? (5)
↑ CO ↑ ventilation ↑ chronotropic ↑ inotropic ↓ vascular resistance
51
Is T3 or T4 responsible for CV effects of TH?
T3
52
TH ↑ glucose absorption, gluconeogenesis, glycogenolysis. What impact does this have on serum glucose? Increase, decreased or maintain normal?
Normal serum glucose
53
Lipolysis and protein catabolism are two effects of TH. Their byproducts (glycerol and amino acids) are essential for what process?
Gluconeogenesis
54
TH stimulates protein synthesis/breakdown. | T or F: This results in a net degradation of tissue protein => neg nitrogen balance.
TRUE
55
What effect does TH have on B-adrenergic receptors (SNS) in cardiac/ skeletal muscles and adipocytes?
Increased synthesis => up regulation => more sensitive to SNS effect
56
How does TH impact fetal development? (4)
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
What hormones regulate the secretion of TH? (5)
1. TRH 2. Dopamine 3. Somatostatin 4. TSH 5. Peripheral T3/T4
58
T3/T4 have a positive or negative feedback effect?
Negative. Will down regulate TSH receptors on thyrotrophs
59
Hepatic sulfation and glucoronide conjugation result in what with regards to TH?
↑ solubility and biliary excretion
60
Does free T3/T3 generated from T4 or T4 have a greater effect on regulating secretion of TH?
T3/ T3 generated from T4
61
Do you have a faster or slower BMR with hypothyroidism?
Slower Hyperthyroidism w/ fast BMR
62
Mutation to NIS gene, Hashimoto's, low iodide diet and Thyroiditis are associated w/ Hyper or Hypothyroidism?
Hypothyroidism
63
T or F: Goiter can be seen with both hyper and hypothyroidism?
TRUE
64
Propylthiouricil (PTU), removal of part or entire thyroid gland, radioactive I and 𝛽-adrenergic antagonist are tx for hyper or hypothyroidism?
HYPERthyroidism
65
Hyperprolactimemia, cold intolerance, cramp and aches are associated w/ HYPER or HYPOthyroidism?
HYPOthyroidism
66
High glycoprotein TG levels, increased uptake of radioactive I tracer, heat intolerance, and muscle weakness are associated w/ HYPER or HYPOthyroidism?
HYPERthyroidism
67
Graves disease (immunoglobulin to TSH receptor) is associated w/ HYPER or HYPOthyroidism?
HYPERthyroidism
68
Pendrin syndrome (hearing loss and low iodide) is associated w/ HYPER or HYPOthyroidism?
HYPOthyroidism

Physio II (14 decks)

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