Thyroid Gland Flashcards Preview

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

Flashcards in Thyroid Gland Deck (32)
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1

where is the thyroid gland located

below the thyroid cartilage

2

what joins the 2 lobes of the gland together

the isthmus

3

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

true

4

describe the embryological development of the thyroid gland

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

5

what are thyroid follicles

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

6

what type of cells are parathyroid glands made up of

principal cells and chief cells

7

what types of cells are thyroid glands made up of

follicular cells and parafollicular cells (bigger)

8

what do parafollicular cells produce

calcitonin

9

what do follicular cells produce

thyroglobulin and the thyroid hormones T3 and T4

10

what does colloid do

store the thyroglobulin

11

what residues are the thyroid hormones made up of

T3 - MIT + DIT
T4 - DIT + DIT

12

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

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

13

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

thyroid peroxidase

14

what does thyroid peroxidase do

- oxidises iodide to iodine
- adds the iodine to the tyrosine residues
- couple the MIT and DIT residues within the thyroglobulin protein

15

how much of the bodys iodine is in the thyroid glands

90-95%

16

how is iodide taken up from the blood

through a sodium iodide symporter

17

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

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

which thyroid hormone is mostly made

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

19

how are T3 and T4 transported in the blood

by being bound to the protein thyroxine-binding globulin

20

how is the hormonal output of the hormones regulated

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

what effect do the thyroid hormones have

- increase metabolic rate
- stimulate metabolic pathways
- increase sympathetic effect

22

describe the structure of the thyroid stimulating hormone

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

23

describe how TSH stimulates the thyroid gland to release the hormones

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

how do the thyroid hormones increase metabolic rate

- increasing number and size of mitochondria
- stimulating synthesis of enzymes in the respiratory chain

25

what do the thyroid hormones stimulate metabolic pathways

- stimulates lipolysis and beta oxidation of fatty acids
- stimulates entry of glucose into cells increasing gluconeogenesis and glycogenolysis

26

how do thyroid hormones increase sympathetic effect

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

27

how do the thyroid hormones affect the cardiovascular system

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

28

how do the thyroid hormones affect the nervous system

increase myelination of nerves and development of neurones

29

where are thyroid hormone receptors found

in the nucleus bound to a specific sequence of DNA

30

what happens when the hormones bind to the thyroid receptor

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