Thyroid Flashcards

1
Q

– butterfly shaped, 2 lobes separated by Isthmus and straddles the trachea

A

Thyroid gland

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2
Q

Largest endocrine gland

A

Thyroid gland; (15-25g)

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3
Q

enumerate the principal cells of the thyroid gland

A
  • Follicular epithelium; T3, T4
  • Parafollicular cells: Calcitonin
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4
Q

What is the main function of the Thyroid gland?

A

produce thyroid hormones. Iodine storage

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5
Q

GIve the normal Thyroid iodide to plasma iodide ratio:

A

25-40:1

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6
Q

TRUE or FALSE: Iodine is needed for hormone synthesis

A

TRUE

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7
Q

Intake for Iodine:
normal intake -
hormone secretion deficiency -

A
  • 1mg/week (150ug/day)
  • <50ug/day
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8
Q

Enumerate the 3 components of the thyroid gland

A
  • Follicles
  • Colloid
  • Thyroglobulin
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9
Q

Responsible for absorbing iodine (ring shape)

A

Follicles

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10
Q

Reservoir of materials for hormone production surrounded by follicle

A

Colloid

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11
Q

TRUE or FALSE: Colloid is rich in glycoprotein thyroglobulin

A

TRUE

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12
Q

this component is with tyrosyl groups (rich in tyrosine)

A

Thyroglobulin

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13
Q

TRUE or FALSE:
Follicle are the major component of colloid

A

FALSE; Thyroglobulin are th emajor component of colloid

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14
Q

TRUE or FALSE: Colloid are synthesized and secreted by follicles

A

FALSE; Thyroglobulin are the ones synthesized and secreted by follicles

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15
Q

which TG component reflects Thyroid mass, injury and TSH receptor stimulation?

A

Thyroglobulin

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16
Q

TRUE or FALSE: Presence of Thyroglobulin indicate tumor (malignant/benign)

A

TRUE

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17
Q

Which following conditions does thyroglobulin seen at increased levels?

A

increase in:
- Graves disease
- thyroiditis
- nodular goiter

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18
Q

The biosynthesis of T3 and T4 is controlled by?

A

Thyroid Stimulating Hormone (TSH)

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19
Q

Enumerate the biosynthesis of TH

A
  1. Iodide trapping/uptake
  2. Oxidation
  3. Iodination of tyrosyl residues by TPO
  4. Coupling/Condensation reaction
  5. Thyroglobulin is then moved to the colloid for storage
  6. Exocytosis of colloid droplets
20
Q

Iodide trapping/uptake is controlled by?

A

Na-Iodide symporter

21
Q

what is the lumen Iodide to follicular iodide ratio?

A

5:1

22
Q

Conversion of iodide to elemental iodide is catalyzed by which enzyme?

A

Thyroid peroxidase (TPO)

23
Q

Where does the iodothyronine formed?

A

optical barrier, follicular cells = Monoiodothyronine & Diiodothyronin

24
Q

DIT + DIT by TPO

A

T4; Thyroxine

25
Q

MIT + DIT

A

T3; Triiodothyronine

26
Q

Transport:
T4 binding proteins
Circulating T4 plasma protein (%)
Free T4 (%)

A

99.95% T4 =Plasma protein,
0.05% = Free

27
Q

T4 percentages:
TBG
TBPA
TBA

A
  • 75% of T4
  • 15=20% of T4
  • 9% of T4
28
Q

TBG is measured by what method?

A

Immunoassay

29
Q

Which substances affect the TBG & T4 binding?

A
  • Salicylates
  • phenytoin
  • penicillin
  • heparin
30
Q

t3 binding protein percentage:

A

0.5% Free

31
Q

t3 binding protein percentage:
TBG
TBPA
TBA

A
  • 99.5%
  • very low
  • none
32
Q

_______ affinity of T3 binding protein
_______ Free T3 in plasma
_______ biological activity of T3 & T4

A
  • decrease
  • increase
  • increase
33
Q

Discuss the hormone loop

A

Metabolism →, detected by Hypothalamus →, Stimulate the pituitary gland →, TSH to target oragen (Thyroid) →, T3, T4 →, Target organ (adrenal medulla) →, Epinephrine & norepinephrine →, increase Metabolism

34
Q

Enumerate the three Thyroid autoantigens

A
  • Thyroperoxidase
  • Thyroglobulin
    TSH receptor
35
Q

What are the Physiologic actions of Thyroid?

A
  1. Basal metabolic Rate
  2. Tissue growth
  3. CNS development
  4. ANS
  5. CV & Respiratory systems
  6. GIT
  7. Skin
  8. Lactogenesis
36
Q

Responsible for deiodination

A

Iodothyronine-5’-deiodinase

37
Q

Which type is abundant for T3 circulation?

A

Type 1

38
Q

Location of Type 1 and Type 2 iodothyronine-5’-deiodinase

A

Type 1 - Liver & Kidney

Type 2 - Brain

39
Q

Which type maintains T3 levels in the CNS?

A

Type 2

40
Q

Main serum carrier of T3 and T4

A

Thyroglobulin

41
Q

Method of choice for TBG level detection

A

immunoassay

42
Q

used to confirm results of FT3 and FT4 or abnormalities in the relationship of total thyroxine and THBR test

A

TBG test

43
Q

Hyperthyroidism vs Euthyroidism

A

Hyperthyroidism - increased thyroxine levels

Euthyroidism - increased binding with TBG and Thyroxine

44
Q

Total serum of T3 and T4 are dependent upon ________

A

amount of TBG

45
Q

Enumerate the conditions associated with increase and decrease TBG levels

A

increased: Hypothyroidism, pregnancy, estrogen, euthyroidism

Decreased: anabolic steroids and nephrosis