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Phase 1 - S2 Metabolism, Endocrinology, Haematology > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

where is the thyroid gland located

A

below the thyroid cartilage

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2
Q

what joins the 2 lobes of the gland together

A

the isthmus

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3
Q

true or false: the thyroid gland is the first endocrine gland to develop

A

true

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4
Q

describe the embryological development of the thyroid gland

A

at the base of the tongue there is epithelia proliferation
this descends down the thyroglossal duct and passes infront of the hyoid bone
the duct then degenerates
the detached thyroid then continues to migrate

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5
Q

what are thyroid follicles

A

spherical shapes lined by simple cuboidal epithelium of follicular cells filled with colloid

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6
Q

what type of cells are parathyroid glands made up of

A

principal cells and chief cells

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7
Q

what types of cells are thyroid glands made up of

A

follicular cells and parafollicular cells (bigger)

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8
Q

what do parafollicular cells produce

A

calcitonin

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9
Q

what do follicular cells produce

A

thyroglobulin and the thyroid hormones T3 and T4

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10
Q

what does colloid do

A

store the thyroglobulin

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11
Q

what residues are the thyroid hormones made up of

A

T3 - MIT + DIT

T4 - DIT + DIT

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12
Q

describe the process of making the thyroid hormones from the tyrosine residues

A

the tyrosine residues on the thyroglobulin undergo iodination
coupling then occurs were the residues couple to become the hormone

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13
Q

what enzyme is required to regulate the production of the thyroid hormones

A

thyroid peroxidase

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14
Q

what does thyroid peroxidase do

A
  • oxidises iodide to iodine
  • adds the iodine to the tyrosine residues
  • couple the MIT and DIT residues within the thyroglobulin protein
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15
Q

how much of the bodys iodine is in the thyroid glands

A

90-95%

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16
Q

how is iodide taken up from the blood

A

through a sodium iodide symporter

17
Q

what happens to the thyroid hormones attached to the thyroglobulin in order to be releases

A

the thyroglobulin is taken into the follicular cells from the colloid by pinocytosis
a lysosome fuses and the enzymes break down the protein to release the hormones

18
Q

which thyroid hormone is mostly made

A

90% is T4 but most of this is converted into T3 in the kidneys and liver

19
Q

how are T3 and T4 transported in the blood

A

by being bound to the protein thyroxine-binding globulin

20
Q

how is the hormonal output of the hormones regulated

A

thyrotropin releasing hormone is produced from the hypothalamus and goes to the anterior pituitary where it causes the release of thyroid stimulating hormone which goes to the thyroid gland to cause the production of the thyroid hormones

21
Q

what effect do the thyroid hormones have

A
  • increase metabolic rate
  • stimulate metabolic pathways
  • increase sympathetic effect
22
Q

describe the structure of the thyroid stimulating hormone

A

glycoprotein hormone composed of 2 non-covalently bound subunits (alpha and beta)

23
Q

describe how TSH stimulates the thyroid gland to release the hormones

A

The TSH binds to a GPCR on the surface of the follicular cell which activates alpha s and q g proteins
this stimulates the iodide uptake and the thyroglobulin production by the cell eventually leading to the production of the hormones

24
Q

how do the thyroid hormones increase metabolic rate

A
  • increasing number and size of mitochondria

- stimulating synthesis of enzymes in the respiratory chain

25
Q

what do the thyroid hormones stimulate metabolic pathways

A
  • stimulates lipolysis and beta oxidation of fatty acids

- stimulates entry of glucose into cells increasing gluconeogenesis and glycogenolysis

26
Q

how do thyroid hormones increase sympathetic effect

A

increase andrengeric receptor number on cells so they increase their uptake of catecholamines

27
Q

how do the thyroid hormones affect the cardiovascular system

A

increases the hearts responsiveness to catecholamines causing positive inotropy and positive chronotropy

28
Q

how do the thyroid hormones affect the nervous system

A

increase myelination of nerves and development of neurones

29
Q

where are thyroid hormone receptors found

A

in the nucleus bound to a specific sequence of DNA

30
Q

what happens when the hormones bind to the thyroid receptor

A

there is a conformational change causing the receptor to activate transcription allowing gene expression

31
Q

what is the section of DNA to which the thyroid receptor is pre bound to called

A

a hormone response element

32
Q

why does the thyroid gland move up when swallowing

A

because it is encased in the pre-tracheal fascia which attaches it to the trachea and larynx

Phase 1 - S2 Metabolism, Endocrinology, Haematology (22 decks)

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