The thyroid gland

Question 1

What is the name for a greatly enlarged thyroid?

Answer 1

Goitre

Question 2

What is TSH?

Answer 2

a pituitary dimeric glycoprotein composed of an alpha and a beta subunit.

Question 3

The alpha subunit is the same as:

Answer 3

TSH
LH
FSH
hCG

Question 4

TSH binds to a G-protein couple receptor on thyroid follicle epithelial cells, which activates both:

Answer 4

• Adenylate Cyclse = cAMP/PKA dependant pathway

- Phospholipase C = PI turnover = DAG and IP3

Question 5

iodine is actively taken up from the blood into follicular cells and transporter into the lumen. in the lumen the enzyme ________ ________ converts iodine to free iodine.

Answer 5

Thyroid peroxidase

Question 6

Thyroglobulin contains a high content of what?

Answer 6

tyrosine

Question 7

Iodine atoms are incorporated into?

Answer 7

Tyrosine residues

Question 8

MIT stands for:

Answer 8

mono-iodotyrosine = one iodine per tyrosine

Question 9

DIT stands for:

Answer 9

Di-iodotryrosine = two iodine per tyrosine

Question 10

DIT + DIT =

Answer 10

T4

Question 11

MIT + DIT =

Answer 11

T3

Question 12

Two ____ do NOT couple

Answer 12

MIT

Question 13

what do lysosomal cells in the follicular cells do?

Answer 13

break down the iodinated thyroglobulin liberating free T3 and T4

Question 14

How does T3 and T4 enter the blood?

Answer 14

Diffuse through the plasma membrane of the follicular cells

Question 15

Inactive DIT and MIT are rapidly?

Answer 15

de-ionated and the released iodine is recycled back to the lumen for further use

Question 16

follicular cells take up a portion of the _____ in the lumen (________)

Answer 16

Colloid

Endocytosis

Question 17

What does TBG stand for?

Answer 17

Thyroxine binding globulin

Question 18

What does TBG circulate bound to?

Answer 18

T3 AND T4, because they have poor solubility in water

Question 19

What does TBG prevent?

Answer 19

Urinary secretion of T3 andT4

Question 20

TBG ____ against ____ changes in the ______ functions

Answer 20

buffers
acute
thyroid

Question 21

before exerting a biological effect what must T3/T4 do?

Answer 21

dissociate from TBG

Question 22

what is secreted 90%; T3 or T4?

Answer 22

T4, T3 is secreted 10%

Question 23

What is more potent T3 or T4?

Answer 23

T3 is 3 fold more potent than T4

Question 24

how is most of secreted T4 activated?

Answer 24

by the removal of an iodine in target peripheral tissues

Question 25

T3 and T4 bind to

Answer 25

intracellular thyroid hormone receptors

Question 26

the receptor that T3 and T4 bind to is a:

Answer 26

HORMONE REPSONSIVE TRANSCRIPTION FACTOR, T3 is more active as it binds with a higher affinity

Question 27

what are the effects of thyroid hormone?

Answer 27

``` -Increases basa metabolic rate (BMR) raised CO2 consumption CO2 production Heat production -Cardiovascular system increased hear force and contraction -Nervous system increases activity of sympathetic nervous system enhances the sensitivity to catecholamines -Growth and maturation embryo development CNS development Linear growth ```

Question 28

How does a goitre come about?

Answer 28

hypertrophy of thyroid gland caused by excessive stimulation by TSH associated with certain forms of hypo or hyper thyroids often associated with autoimmune disease

Question 29

Effects of Hypothyroidism in Adults:

Answer 29

``` weight gain cold intolerance lethargy depression puffiness of skin and muscles sluggish reflexes muscular weakness reduced pulse rate and cardiac output ```

Question 30

Effects of hypothyroidism in foetus/child

Answer 30

brain damage - permanent if not treated early enough shortness obesity mental retardation

Question 31

What is done to prevent foetus/child hypothyroidism?

Answer 31

routine neonatal screening for elevated TSH. | High TSH indicated low T3/T4 due to reduced -ve feedback on hypo. pit

Question 32

Iodine Deficiency Disorder (IDD) is the worlds most prevalent cause of?

Answer 32

brain damage

Question 33

how many people worldwide does it effect?

Answer 33

740 million, 200 million with goitre

Question 34

IDD is easily avoided by?

Answer 34

use of iodised cooking salt/supplementary iodine in foods

Question 35

What is the treatment for HYPOthyroidism?

Answer 35

lifelong replacement of T4 (adult ~150ug/day), unless due to chronic dietary iodine deficiency in which case increased supplementary iodine is given in diet.

Question 36

What are the causes of hypothyroidism?

Answer 36

- Primary failure of thyroid gland - Secondary due to hypothalamic or anterior pituitary failure - Secondary due to autoimmune damage to gland - Secondary due to chronic lack of dietary iodine

Question 37

What is HYPERthyroidism?

Answer 37

excess thyroid hormone

Question 38

what are the symptoms of hyperthyroidism?

Answer 38

``` weight loss nervousness heat intolerance high cardiac output hand tremors eyeball protusion ```

Question 39

50% of hyperthyroidism are due to _________

Answer 39

Grave's disease

Question 40

What causes graves disease?

Answer 40

autoimmune disease thyroid stimulating Ab that mimics TSH: Primary = hyper secreting thyroid tumour secondary= excessive hypothalamic/anterior pituitary secretion

Question 41

What is the treatment for hyperthyroidism?

Answer 41

anti-thyroid drugs that interfere with thyroid hormone synthesis surgical resection of thyroid thyroid ablation using radioactive iodine

Question 42

Elevated ___ inhibits the release of ___ and ___ = _______ __________

Answer 42

T3 TSH TRH negative feedback