7.3

Question 1

What are the 2 thyroid hormones?

Answer 1

T3= Triiodothyronine
T4= Thyroxine

Question 2

What is NIS

Answer 2

Na/I cotransporter

Question 3

What can compete the I- on the NIS?

Answer 3

Thyocyanate (SCN-)

Pertechnate (TcO4-)

Question 4

How does Iodine pumped ot to the colloid?

Answer 4

Pendrin- Cl/I antiporter

Question 5

What oxidize I- to I2?

Answer 5

Thyroid Peroxidase (TOP)
With the help of DUOX2

Question 6

How does T3,T4 circulate in the blood?

Answer 6

80% bound to TBG
15% bound to Transthyretin
5% bound to Albumin

Question 7

How much of T3, T4 is free?

Answer 7

0. 5% of T3 is free

0. 02% of T4 is free

Question 8

What happens to thyroid hormones in hepatic failure?

Answer 8

TBG levels drop -> increase in free thyroid hormones -> negative feedback -> less thyroid hormones are produced

Question 9

When can an increase in TBG happen?

Answer 9

Pregnancy

Question 10

What happens to T4when its absorbed by a tissue?

Answer 10

5’ Iodinase converts T3 to T4

Question 11

When do 5’ Iodinase being inhibited?

Answer 11

During starvation in skeletal muscle to allow lower metabolic rate

Question 12

What can decrease 5’ Iodinase activity?

Answer 12

Starvation
Pregnancy
Stress
Hepatic failure
Renal failure

Question 13

What can increase 5’ Iodinase activity?

Answer 13

Obesity

Question 14

Types of 5’ Iodinase

Answer 14

Type 1: T4->T3 in kidney, liver, skeletal muscle
Type 2: T4->T3 in CNS, Pituitary
Type 3: T4->rT3 Inactivation

Question 15

What happens after the conversion of T4 to T3 inside the target cell?

Answer 15

T3 binds thyroid receptor on the nuclear membrane -> get inside nucleus and find Thyroid Responsive Element on DNA with RXE

Question 16

(Thyroid Hormones Effects)

Effects on Basal Metabolic rate?

Answer 16

Increase O2 consumption (except brain, gonads, spleen)

This will increase body heat

Question 17

(Thyroid Hormones Effects)

Metabolism?

Answer 17

Increase glucose absorption
Gluconeogenesis
Glycogenolysis
Protein synthesis
Protein degradation 

General catabolic effect

Question 18

(Thyroid Hormones Effects)

Cardiovascular?

Answer 18

Increase CO
Increase SV, HR
All by induce B1 adrenergic R in the heart (will increase sympathetic activity)

Question 19

(Thyroid Hormones Effects)

Respiratory?

Answer 19

Rate and minute volume increases

Erythropoietin stimulated -> RBC synthesis increases

Question 20

(Thyroid Hormones Effects)

Growth?

Answer 20

Thyroid hormones work with GH and Somatomedins to promote general growth

Question 21

(Thyroid Hormones Effects)

CNS?

Answer 21

Myelination - childhood
Synapses formation - childhood
Cell migration - childhood

Question 22

(Thyroid Hormones Effects)

Autonomic NS?

Answer 22

Induce expression of a and B adrenergic R

Question 23

Structure of TSH

Answer 23

a subunit is non specific

B subunit is specific to TSH

Question 24

How does TSH stimulate T3/T4 production?

Answer 24

1. Increase NIS (I uptake, Iodination, TG endocytosis)
2. mRNA synthesis for TPO, DUOX2, NIS
3. Increase cell number and size (Goiterrr)

Question 25

What will stimulate the Hypothalamus to secrete TRH

Answer 25

Increased food intake

Decreased temparture

Question 26

What are the causes for Hypothyroidism?

Answer 26

Iodine deficiency
Genetic issues
Inflammation

Question 27

Symptoms in infants of Hypothyroidism?

Answer 27

Cretinism (mental retardation, dwarfism, big tongue)

Question 28

Symptoms in adults of Hypothyroidism?

Answer 28

1. Myxoedema- proteoglycans and glycoproteins are high in CT (usually TH breaks them)
2. Hoarse voice
3. Dry skin
4. Weight gain
5. Sensitive to cold
6. Slow speech
7. Depression

Question 29

What are the causes for Hyperthyroidism?

Answer 29

Increased TSH

TSH like antibodies (Graves disease)

Question 30

Symptoms of Hyperthyroidism?

Answer 30

1. Increased BMR
2. Muscle weakness
3. Anxiety