Thyroid Anatomy and Physiology

Question 1

What structure joins to two lobes of the thyroid

Answer 1

isthmus

Question 2

where are the parathyroid glands

Answer 2

the posterior 4 corners of the thyroid gland

Question 3

what does the thyroid secrete

Answer 3

thyroid hormone

Question 4

what does the parathyroid secrete

Answer 4

parathyroid hormone

controls calcium

Question 5

what does the thyroid hormone do

Answer 5

allows you to convert what you eat into energy

Question 6

where does the thyroid sit

Answer 6

between 5th cervical and 1st thoracic vertebrae

Question 7

What nerve supplies the thyroid

Answer 7

parasympathetic from vagus nerve

sympathetic from superior, inferior and middle ganglia fo the sympathetic trunk

Question 8

what nerve is at risk of being damaged near the thyroid

Answer 8

recurrent laryngeal nerve

Question 9

what do the follicular cells of a thyroid follicle surround

Answer 9

colloid-tyrosine-containing thyroglobulin filled spheres

Question 10

what do parafollicular C cells secrete

Answer 10

calcitonin

Question 11

what do follicular cells synthesise

Answer 11

thyroid hormones

T3 and T4

Question 12

what is needed to create thyroid hormone

Answer 12

iodine

Question 13

what is the structure of the thyroid hormone

Answer 13

4 iodine molecules stuck to tyrosine residues on thyroglobulin

Question 14

What is T3

Answer 14

coupling of MIT and DIT

monoiodotyrosine unit and di-iodntyrosine unit

Question 15

what is T4

Answer 15

coupling of 2 DITS

Question 16

what hormone is 90% of the hormone produced in the thyroid gland

Answer 16

T4 (4 iodines)

Question 17

what hormone is 10% of the hormone produces in the thyroid

Answer 17

T3 (3 iodines)

Question 18

how much more potent is T3 than T4

Answer 18

4 times more potent

Question 19

which thyroid hormone is more biologically active

Answer 19

T3

Question 20

why do T3 and T4 bind to plasma proteins in the blood

Answer 20

they are hydrophobic so cannot dissolve in the blood

Question 21

what proteins do the thyroid hormone bind to

Answer 21

Albumin (5%)
thyroxine binding globulin (70%)
thyroxine binding prealbumin (20%)

Question 22

what happens to T4 when it arrives at the cell

Answer 22

its changed to T3 by removal of an iodine

Question 23

what is unbound thyroid hormone in the blood

Answer 23

biologically active form

Question 24

what is measures in a blood test for thyroid hormone

Answer 24

just the free unbound hormone as thats the bit thats biologically active

Question 25

what puts you're thyroxine binding globulin up

Answer 25

pregnancy newborn state OCP and other sources of oestrogen others

Question 26

what does hyperthyroidism do

Answer 26

``` affects every tissue in the body CNS- anxiety, sweating Heart- increased HR, palpitations GI- loose bowels, diarrhoea loose periods ```

Question 27

what does thyroid hormone affect

Answer 27

``` metabolism growth development reproduction behaviour ```

Question 28

what affect to thyroid hormones have on metabolic rate and thermogenesis

Answer 28

increases them

Question 29

thyroid hormone affects of metabolism of carbs, lipids and proteins

Answer 29

increases all 3

Question 30

why is the thyroid important in children

Answer 30

growth hormone production and secretion development of foetal and neonatal brain normal central nervous system activity

Question 31

what affect does hypothyroidism have on the brain

Answer 31

slow intellectual functions

Question 32

what affect does hyperthyroidism have on brain

Answer 32

nervousness, hyperkinesis and emotional liability

Question 33

what do thyroid hormones increase responses to

Answer 33

adrenaline sympathetic NS neurotransmitter noradrenaline by increasing number or receptors cardiovascular responsiveness also increased

Question 34

what stimulates thyroid hormone release

Answer 34

thyrotrophin releasing hormone (TRH) from hypothalamus stimulates thyroid this causes thyroid stimulating hormone (TSH) release from anterior pituitary this stimulates release of T3 and T4

Question 35

how is thyroid hormone release controlled

Answer 35

negative feedback from T3 and T4 controls release of TRH and TSH

Question 36

what external factors affect thyroid hormone release

Answer 36

cold terperatures stimulate TRH release in babies and young children stress inhibits TRH and TSH release Circadian rhythms - thyroid hormones highest late at night

Question 37

what do de-Iodinase enzymes do

Answer 37

addition or removal of an iodine atom to change T4 to T3 or vis versa

Question 38

where is de-iodinase type 1 found

Answer 38

liver and kidney - reserves incase there isn't enough in other cells

Question 39

where is de-iodinase type 2 found

Answer 39

in the heart and skeletal muscle, CNS, fat, thyroid and pituitary

Question 40

Where is type 3 de-iodinase found

Answer 40

in fatal tissue and placenta and brain

Question 41

what is hypothyroidism

Answer 41

``` not enough thyroid hormone no negative feedback TRH and TSH increase T3 and T4 decrease can be caused by lack of iodine in diet (can be associated with goitre, swollen neck?) ```

Question 42

symptoms of hypothyroidism

Answer 42

reduced basal metabolic rate slow pulse rate fatigue, lethargy, slow response times and mental sluggishness cold intolerance tendency to put on weight easily in adults - myxoedema (puffy face, hands and feet) in babies- cretinism (dwarfism and limited mental functioning due to deficiency of thyroid hormones present at birth)

Question 43

what is graves disease

Answer 43

autoimmune disease- thyroid stimulating immunoglobulin that acts like TSH but doesn't have negative feedback by T3 and T4 can cause bulging eyes due to water retaining carb built up behind eyes goitre -enlarged thyroid gland

Question 44

symptoms of hyperthyroidism

Answer 44

``` increases basal metabolic rate fast pulse rate increased nervousness and excessively emotional insomnia sweating and heat intolerance tendency to loss weight easily ```