Thyroid Physiology

Question 1

What 3 things does the thyroid gland secrete?

Answer 1

thyroxine; tri-iodothyronine; calcitonin

Question 2

What vertebral ring is the thyroid found at?

Answer 2

between C5 and T1

Question 3

What tracheal rings is the thyroid found at?

Answer 3

2nd-4th tracheal rings

Question 4

What is the sympathetic innervation of the thyroid?

Answer 4

superior, middle and inferior ganglia of the sympathetic trunk

Question 5

What is the parasympathetic innervation of the thyroid gland?

Answer 5

vagus nerve

Question 6

What artery do the superior and inferior thyroid arteries branch from?

Answer 6

external carotid

Question 7

What veins do the superior and middle thyroid veins drain into?

Answer 7

internal jugular

Question 8

What vein does the inferior thyroid vein drain into?

Answer 8

brachiocephalic

Question 9

What ligament attaches the posteriomedial aspec of the thyroid gland?

Answer 9

Berry ligament

Question 10

How are T3 and T4 exported from the colloid?

Answer 10

pinocytosis

Question 11

What are the two units used in T3 and T4?

Answer 11

monoiodotyrosine and di-iodotyrosine

Question 12

What is the coupling of units in T3?

Answer 12

MIT and DIT

Question 13

What is the coupling of units in T4?

Answer 13

2 DITs

Question 14

Where are T3 and T4 stored?

Answer 14

colloid thyroglobulin

Question 15

What is the basic molecule from which T3 and T4 are synthesised?

Answer 15

thyroglobulin

Question 16

What attaches to thyroglobulin?

Answer 16

iodine

Question 17

What drugs inhibit the attachment of iodine to thyroglobulin?

Answer 17

carbimazole and propylthiouracil

Question 18

What is the name of T4?

Answer 18

thyroxine

Question 19

What is the name of T3?

Answer 19

triiodothyronine

Question 20

What is the difference in potency between T3 and T4?

Answer 20

T3 is about 4 times more potent than T4

Question 21

How do T3 and T4 travel in the blood?

Answer 21

bound to plasma proteins

Question 22

What plasma proteins do T3 and T4 bind to?

Answer 22

thyroxine binding globulin; thyroxine binding prealbumin; albumin

Question 23

How do thyroid hormones increase basal metabolic rate?

Answer 23

increase number and size of mitochondria; increase oxygen use and rates of ATP hydrolysis and increase synthesis of respiratory chain enzymes

Question 24

What do thyroid hormones do in terms of body temperature?

Answer 24

increase thermogenesis

Question 25

How are thyroid hormones involved in the metabolism of food

Answer 25

stimulate glycogenolysis nad gluconeogenesis and glucose uptake; increase fatty acid oxidation in tissues; increse protein synthesis

Question 26

What effects does hypo and hyper thyroidism have on CNS actviity?

Answer 26

hypo- slow intellectual functions; hyper- nervousness; hyperkinesis and emotional lability

Question 27

What is the use of thyroids in foetal develpment?

Answer 27

myelinogensis and axonal growth require thyroid hormones

Question 28

what is the effect of thyroid hormones on the sympathetics?

Answer 28

increase responsiveness to adrenaline and sympathetic noradrenaline by increasing numbers of receptors

Question 29

What does this permissive sympathomimetic action ahve on the CVS?

Answer 29

increases force and rate of contraction

Question 30

What hormone released by the hypothalamus stimulates the anterior pituitary?

Answer 30

thyrotrophin releasing hormone

Question 31

what hormone does the anterior pituitary release to stimulate T3 and T4 release?

Answer 31

thyroid stimulating hormone

Question 32

What effect do T3 and T4 have on TRH and TSH

Answer 32

exert negative feedback control

Question 33

What enzymes are involved in the activati onand deactivation of thyroid hormone?

Answer 33

delodinase enzymes

Question 34

How do the delodinase enzymes work?

Answer 34

add or remoave an iodine atom from the outer ring

Question 35

what enzyme converts T4 to T3 in tissues?

Answer 35

D2

Question 36

Where is D2 found?

Answer 36

in the heart, SK, CNS, fat, thyroid, pituitary

Question 37

What are symptoms of hypothyroidism?

Answer 37

decreased BMR; slow pulse rate; fatigue; lethargy; slow response times and mental sluggishness; cold-intolerance

Question 38

How does thryoid stimulating immunoglobulin work?

Answer 38

like TSH but is unchecked by T3 and T4

Question 39

What are the symptoms of hyperthyroidism?

Answer 39

increased BMR; HR; nervousness and excessively emotional; insomnia; sweating and heat intolerance