Thyroid Gland

Question 1

Hormone secreted by thyroid gland

Answer 1

1. Thyroxine (T4) = 93%
2. Triiodothyronine= 7%
3. Calcitonin

Question 2

What is the role of calcitonin

Answer 2

Role in maintaining Ca2 + and phosphate

Question 3

T4 + T3 require for what

Answer 3

Maintain basal metabolic rate

Question 4

What is basal metabolic rate

Answer 4

Chemical reaction in body that consuming nutrient + oxygen to produce energy, heat + carbon dioxide

Question 5

How change in thyroid hormone release affect metabolic rate (inc. / dec.)

Answer 5

1. Chronic lack = dec. Metabolic rate to 40 -50% = feel cold + gain weight
2. Chronic excessive = inc. metabolic rate 60 - 100% = feel hot + loose weight

Question 6

How is iodine found in body

Answer 6

• 1mg / week iodine required for normal thyroid function
• get iodine from iodide ingested orally to get

Question 7

How iodide reach thyroid

Answer 7

-thyroid gland has pump to actively transport iodide from blood = iodide trapping
-only 20% taken from blood = 30 time higher concentration in thyroid than blood

Question 8

Parts of thyroid gland

Answer 8

-compose many follicles ( 100-30l um diamter) filled with colloid
-coloid composed glycoprotein= thyroglobulin = contain thyroid hormone

Question 9

How T4 and T3 formed

Answer 9

Combine 2 tyrosine + 3/4 iodide molecule ( peroxidase need to add them up
Then th remain attach thyroglobulin

Question 10

What thyroglobulin contain

Answer 10

70 tyrosine amino acid

Question 11

What happen with TH when its formed

Answer 11

Thyroglobulin secrete into follicular colloid to be stored = stored for 2-3 months

Question 12

Mechanism in which T4 +T3 are release form thyroid gland

Answer 12

1. Thyroid send pseudopod that close around small portion colloid
2. Lysosome in cell fuse vesicle = form digestive enzyne
3. Proteinase ( on of enzyme) digest thyroglobulin + release T3 + T from thyroglobulin
4. Diffuse through thyroid into blood
5. Cycling iodine in cell to produce additional TH

Question 13

Processus in which T3 become T4

Answer 13

• at beginning 93% T4
  In few days, T4 become T3 through deiodinated = removal iodine from T4)
• hormone used by tissue is T3

Question 14

3 plasma binding protein to which 53 +T4 bind in blood

Answer 14

1. Thyroxine-binding glbulin
2. Thyroxine-binding prealbumin
3. Albumin

Question 15

Once reach tissue bind with what

Answer 15

Intracellular protein

Question 16

What is the latency period for thyroxine after injection

Answer 16

2-3 days
Then reach max 10-12 days
Then decrese half-life 15 days

Question 17

Latency period T3

Answer 17

-4x faster
6-12 hours
Max activity 2-3 days (* plasma protein has higher affinity thyroxine = release T4 slower than T3)

Question 18

What is the general effect of TH

Answer 18

Cause nuclear transcription of genes for synthesizing large nb substance like
-enzyme
- structural protein
-transport protein
- others..

Question 19

Mechanism of effect of hormone

Answer 19

1.T4 deiodinated into T3 = 90% hormone bind receptor is T3
2. Binds intracellular receptor = complex attached DNA genetic strands
3. Activate transcription process
4. RNA formed = new type protein form on cytoplasmic ribosome

Question 20

Effect TH on mitochondria

Answer 20

• inc. number mitochondria
• inc. total membrane surface area mitochondria = inc. formation ATP help cell function

Question 21

Effect TH on carbohydrate metabolism

Answer 21

• inc. absorption rate glucose from gastrointestinal tract
  -inc. uptake rate glucose by cell
• enhance glycolysis ( use glucose for energy through anaerobic conversion glucose to lactic acid)
  -enhance glucogenesis ( formation glycogen from fat/protein)
• inc. insulin secretion = inc. glucose uptake
  -dec. Glycogen stores in liver + skeletal m. (Glycogenesis = more glucose circulation)

Question 22

Effect TH on fat metabolism

Answer 22

• inc. lipolysis = breakdown triglyceride into fatty acid
• inc. free catty acid concentration in plasma
• acc. Oxidative free fatty acid by cell
  -dec. Quantity cholesterol, phospholipids + triglyceride in plasma ( inc. secretion rate cholesterol in bile = loss cholesterol in feces)
• in helatic cell, promote fat anabolism = novo lipogenesis= creation new triglyceride from glucose, glycerol + free fatty acid