session 9-thyroid gland

Question 1

the 2 thyroid lobes are connected by what?

Answer 1

isthmus

Question 2

The thyroid is made up of what 2 types of cells and how are they arranged?

Answer 2

• follicular cells- make up follicles (spherical structures with lumen containing protein, colloid, surrounded by follicle cells)
• parafollicular (c-cells)-found in connective tissue (connective tissue separated follicles

Question 3

what type of epithelia are follicular cells?

Answer 3

cuboidal or columnar

Question 4

what 3 hormones are made by the thyroid and where are they made?

Answer 4

• t3 and t4 made in follicular cells

- calcitonin made in parafollicular cells

Question 5

what are t3 and t4 made from?

Answer 5

amino acid tyrosine with addition of iodine

Question 6

which one,t3 or t4 is more active and which is stable?

Answer 6

t4 stable and converted to t3

t3 active

Question 7

what is the role of calcitonin?

Answer 7

reduce blood calcium levels (opposite to PTH)

Question 8

how are T3 and T4 synthesised?

Answer 8

• transport of iodide into epithelial cells against concn gradient (coupled with 2 Na2+ ions)
• SYNTHESIS of tyrosine rich protein, thyroglobulin in epithelial cells
• EXOCYTOSIS of thyroglobulin into lumen containing colloid protein
• IODINATION of side chains of tyrosine residues to form MIT (monoiodotyrosine) and DIT (di iodotyrosine)
• coupling of DIT and MIT=T3
• coupling of DIT and DIT=T4

Question 9

where are T3 and T4 stored prior to secretion?

Answer 9

thyroid follicle lumen

Question 10

why are T3 and T4 bound to proteins and which 3 proteins?

Answer 10

hydrophobic

TBG (thyroxine binding globulin),pre albumin, albumin

Question 11

what are the names of T3 and T4?

Answer 11

T3=tri-idothyronine

T4=thyroxine

Question 12

what effect does the trophic hormone TSH have on follicle cells?

Answer 12

increases vascularity (visibly prominent veins), increases size and number of follicle cells
could lead to enlarged thyroid (GOITRE)

Question 13

what do T3 and T4 do?

Answer 13

increase metabolic rate of tissues:

• increase glucose uptake then metabolism
• stimulates fatty acid oxidation (metabolism/break down for energy)
• protein metabolism

Question 14

where is the thyroid gland located?

Answer 14

anterior (towards the front of body) to the larynx and trachea
inferior (below) thyroid cartilage

Question 15

what else are T3 and T4 important for besides metabolim (catab)?

Answer 15

• normal growth and development
• synthesis of heart muscle (myocardium) protein
• bone mineralisation
• hyperplasia assistance
• myelination assistance
• increase RECEPTOR SYNTHESIS

Question 16

With absence of thyroid hormone from birth-puberty, what condition arises?

Answer 16

cretinism (mental and physical retardation)

Question 17

What do thyroid hormones do in the nucleus?

Answer 17

bind to receptors and increase protein synthesis, increases cell activity and thus demand for energy

Question 18

what is the main disease caused by hypothyroidism?

Answer 18

hashimotos disease

Question 19

what 2 things can cause hashimotos?

Answer 19

-destruction of follicles OR
- production of antibody that blocks TSH receptor, decreasing T3,T4 and calcitonin hormone production
AUTOIMMUNE

Question 20

how is hashimotos treated and what is a possible secondary problem with doing this?

Answer 20

oral thyroxine

-over treatment=hyperthyroidism

Question 21

give 3 other causes of hypothyroidism

Answer 21

• post surgery
• lack of iodine
• lack of TSH (secondary)
• radioactive iodine treatment (destroys follicle cells)

Question 22

give 5 signs of hypothyroidism in adults

Answer 22

• bradycardia
• dry and flaky skin
• cold intolerance
• fatigue
• weakness
• weight gain
• alopecia
• deep and husky voice

Question 23

what is a common hyperthyroidism disease?

Answer 23

grave’s disease

Question 24

what happens that causes grave’s disease?

Answer 24

autoimmune disease in which antibodies are produced that stimulate TSH receptors on follicle cells to produce more T3 and 4

Question 25

what is the treatment for graves disease?

Answer 25

carbimazole-inhibits addition of iodine onto thyroglobulin radioactive iodine-destroys follicular cells Remove parts of thyroid-reduce T3 and 4 production

Question 26

what are 3 other causes of hyperthyroidism?

Answer 26

-excessive t3/4 therapy -excess iodine -thyroid carcinoma ectopic thyroid tissue

Question 27

give 5 symptoms of hyperthyroidism

Answer 27

``` heat intolerance tachycardia weight loss hyperactivity exopthalmos (bulging/protruding eyes) skeletal and cardiac myopathy=tiredness,weakness,breathlessness osteoporosis ```

Question 28

In euthyroid, hyperthyroid and hypothyroid conditions, what happens to free T4 and TSH levels?

Answer 28

euthyroid-normal, normal hyperthyroid-high T4, low TSH (neg feedback) hypothyroid-low T4, high TSH (neg feedback)