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Metabolism > session 9-thyroid gland > Flashcards

session 9-thyroid gland Flashcards

1
Q

the 2 thyroid lobes are connected by what?

A

isthmus

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2
Q

The thyroid is made up of what 2 types of cells and how are they arranged?

A
  • follicular cells- make up follicles (spherical structures with lumen containing protein, colloid, surrounded by follicle cells)
  • parafollicular (c-cells)-found in connective tissue (connective tissue separated follicles
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3
Q

what type of epithelia are follicular cells?

A

cuboidal or columnar

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4
Q

what 3 hormones are made by the thyroid and where are they made?

A
  • t3 and t4 made in follicular cells

- calcitonin made in parafollicular cells

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5
Q

what are t3 and t4 made from?

A

amino acid tyrosine with addition of iodine

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6
Q

which one,t3 or t4 is more active and which is stable?

A

t4 stable and converted to t3

t3 active

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7
Q

what is the role of calcitonin?

A

reduce blood calcium levels (opposite to PTH)

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8
Q

how are T3 and T4 synthesised?

A
  • transport of iodide into epithelial cells against concn gradient (coupled with 2 Na2+ ions)
  • SYNTHESIS of tyrosine rich protein, thyroglobulin in epithelial cells
  • EXOCYTOSIS of thyroglobulin into lumen containing colloid protein
  • IODINATION of side chains of tyrosine residues to form MIT (monoiodotyrosine) and DIT (di iodotyrosine)
  • coupling of DIT and MIT=T3
  • coupling of DIT and DIT=T4
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9
Q

where are T3 and T4 stored prior to secretion?

A

thyroid follicle lumen

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10
Q

why are T3 and T4 bound to proteins and which 3 proteins?

A

hydrophobic

TBG (thyroxine binding globulin),pre albumin, albumin

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11
Q

what are the names of T3 and T4?

A

T3=tri-idothyronine

T4=thyroxine

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12
Q

what effect does the trophic hormone TSH have on follicle cells?

A 
increases vascularity (visibly prominent veins), increases size and number of follicle cells
could lead to enlarged thyroid (GOITRE)
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13
Q

what do T3 and T4 do?

A

increase metabolic rate of tissues:

  • increase glucose uptake then metabolism
  • stimulates fatty acid oxidation (metabolism/break down for energy)
  • protein metabolism
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14
Q

where is the thyroid gland located?

A

anterior (towards the front of body) to the larynx and trachea
inferior (below) thyroid cartilage

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15
Q

what else are T3 and T4 important for besides metabolim (catab)?

A
  • normal growth and development
  • synthesis of heart muscle (myocardium) protein
  • bone mineralisation
  • hyperplasia assistance
  • myelination assistance
  • increase RECEPTOR SYNTHESIS
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16
Q

With absence of thyroid hormone from birth-puberty, what condition arises?

A

cretinism (mental and physical retardation)

17
Q

What do thyroid hormones do in the nucleus?

A

bind to receptors and increase protein synthesis, increases cell activity and thus demand for energy

18
Q

what is the main disease caused by hypothyroidism?

A

hashimotos disease

19
Q

what 2 things can cause hashimotos?

A

-destruction of follicles OR
- production of antibody that blocks TSH receptor, decreasing T3,T4 and calcitonin hormone production
AUTOIMMUNE

20
Q

how is hashimotos treated and what is a possible secondary problem with doing this?

A

oral thyroxine

-over treatment=hyperthyroidism

21
Q

give 3 other causes of hypothyroidism

A
  • post surgery
  • lack of iodine
  • lack of TSH (secondary)
  • radioactive iodine treatment (destroys follicle cells)
22
Q

give 5 signs of hypothyroidism in adults

A
  • bradycardia
  • dry and flaky skin
  • cold intolerance
  • fatigue
  • weakness
  • weight gain
  • alopecia
  • deep and husky voice
23
Q

what is a common hyperthyroidism disease?

A

grave’s disease

24
Q

what happens that causes grave’s disease?

A

autoimmune disease in which antibodies are produced that stimulate TSH receptors on follicle cells to produce more T3 and 4

25
Q

what is the treatment for graves disease?

A

carbimazole-inhibits addition of iodine onto thyroglobulin
radioactive iodine-destroys follicular cells
Remove parts of thyroid-reduce T3 and 4 production

26
Q

what are 3 other causes of hyperthyroidism?

A

-excessive t3/4 therapy
-excess iodine
-thyroid carcinoma
ectopic thyroid tissue

27
Q

give 5 symptoms of hyperthyroidism

A 
heat intolerance
tachycardia
weight loss
hyperactivity
exopthalmos (bulging/protruding eyes)
skeletal and cardiac myopathy=tiredness,weakness,breathlessness
osteoporosis
28
Q

In euthyroid, hyperthyroid and hypothyroid conditions, what happens to free T4 and TSH levels?

A

euthyroid-normal, normal
hyperthyroid-high T4, low TSH (neg feedback)
hypothyroid-low T4, high TSH (neg feedback)

Metabolism (14 decks)

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