Thryroid hormones

Question 1

Stages of manufacturing of thyroid hormones

Answer 1

Iodine (I) +tyrosine -> monoiodotyrosine (MIT)
MIT +I -> diiodotyrosine (DIT)
DIT+DIT -> thryoxine (T4)
DIT + MIT -> triiodothryonine (T3)

Question 2

Where does T4 become T3? and how

Answer 2

Liver to kidney and due to 5’deiodinase - I

Question 3

Why does T4 need to be converted to T3?

Answer 3

To be able to to fully able to exert its biological availaibility

Question 4

What basic metabolic effects will T3 and T4 have?

Answer 4

increased calorigenic effect
increased O2 consumption
increased BMR

Question 5

Carbohydrate metabolic features of T3 and T4

Answer 5

There is an increased absorption of glucose from hte GIT
increase in insulin secretion which leads to glucose oxidation
increase in gluconeogenesis which leads to glycogen degredation

Question 6

lipid metabolic features of T3 and T4

Answer 6

• lipolysis increased leading to an increase in FFA levels
• accelerates FFA oxidation
• decrease in cholesterol, triglycerides, phospholipids and plasma

Question 7

impact of T3/4 on the heart

Answer 7

increase in HR CO SBP
decrease in DBP
increase in blood flow to skin

Question 8

impact of T3/4 on GIT

Answer 8

increased appetite, secretion of digestive juices, GIT motility

Question 9

impact of T3/4 on lungs

Answer 9

increase in ventilation rate

Question 10

impact of T3/4 on nervous system

Answer 10

Increase in synaptic activity

enhances the effects of the sympathetic nervous system

Question 11

How does the hypothalamus and pituitary regulate the circulating levels of hormone

Answer 11

stress -ve input 
cold +ve input 
hypothalamus will release TRH 
causing the ant pit to release TSH 
thyroid will then release T3 and T4

Question 12

What is the impact of TSH action on the thyroid gland

Answer 12

Increase in blood flow at thyroid level
increase in iodine trapping and binding
increase in size and number of follicular cells
promotion of endocytosis into follicular cells
stimulation of T3 and T4 synthesis
promotion of thyroglobulin secretion in colloid

Question 13

What are the 4 different causes of hypothyroidism

Answer 13

1. Thyroiditis
2. Severe iodine deficiency
3. severe deficiency of 1 or more synthesis enzymes
4. removal/ destruction of thyroid gland

Question 14

What is primary hyperthyroidism

Answer 14

problem with the thyroid gland

failure of thyroid gland to respond to TSH

Question 15

What can primary hypothyroidism lead to

Answer 15

Elevated TSH levels reuduced -ve feedback

thyroid enlargement and goitre formed

Question 16

What is secondary hypothyroidism and what can it lead to

Answer 16

Deficient TSH production

thyroid atrophy

Question 17

What is tertiary hypothyroidism

Answer 17

deficient TSH secretion due to deficient TRH secretion

Question 18

What are the developmental consequences of hypothyroidism

Answer 18

Congential hypothyroidism

ealry diagnosis is essential

Question 19

3 different causes of Hypothyroidism

Answer 19

autoimmune disease- graves disease
thyroid adenoma
innappropiate TSH secretion (rare)

Question 20

Look at the different signs symptoms and features of hyper/hypothyroidism

Answer 20

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