W.12: Disturbances of Thyroidal Function

Question 1

What is transporting iodide from follicular cell to colloid?

Answer 1

Pendrin (Na-dependent Cl/I- transporter)

Question 2

What is transporting T3 and T4 from thyroid follicle into blood?

Answer 2

MCT: Monocarboxylate transporter

Question 3

Hypothalamus releases what hormone to stimulate the pituitary?

Answer 3

Thyroid releasing hormone (TRH)

Question 4

Pituitary releases what hormone to stimulate the thryoid?

Answer 4

Thyroid stimulating hormone (TSH)

Question 5

Free T3 and T4 has ….. feedback on the pituiary and hypothalamus

Answer 5

Negative

Question 6

T4 can be converted to two other substances..?

Answer 6

T3 and rT3 (reverse T3, ineffecvtive)

Question 7

Half life of T4

Answer 7

1 week

Question 8

Half life of T3

Answer 8

1 day

Question 9

% of T4 bound to TBG

Answer 9

70%

Question 10

% of T4 bound to TBPA

Answer 10

20%

Question 11

% of T4 bound to albumin

Answer 11

9.96%

Question 12

% of T4 unbound (free)

Answer 12

0.04%

Question 13

Type 1 deiodinase found in?

Answer 13

Liver and kidney

Question 14

Type 2 deiodinase found in?

Answer 14

Pituitary, placenta, brain

Question 15

Type 3 deiodinase function?

Answer 15

T4 to rT3

Question 16

4 actions of TSH on thyroid

Answer 16

1. Stimulate iodine uptake
2. Hormonogenesis
3. Release of T3 and T4 (via cAMP)
4. Inc. thyroid gland size and vascularity

Question 17

How does thyroid hormone affect fetal development?

Answer 17

Affecting neural and skeletal system

Question 18

How does thyroid hormone affect oxygen consumption and heat production?

Answer 18

Controls BMR, T3 is considered the major regulator of mitochondrial activity

Question 19

How does thyroid hormone affect the sympathetic system?

Answer 19

Similar to the effects caused by catecholamines

Question 20

How does thyroid hormone affect the endocrine system?

Answer 20

Inc. cortisol metabolism and clearance

Question 21

How does thyroid hormone affect the musculoskeletal system?

Answer 21

Inc. the turnover of bone

Question 22

Values of hormones in hypothryoidism

Answer 22

• TSH > 4.2mIU/L

- Free T4 is low

Question 23

Values of hormones in subclinical hypothyroidism

Answer 23

• TSH > 4.2mIU/L

- Free T4 is normal

Question 24

Values of hormones in euthyroid

Answer 24

• TSH 0.3-4.2 mIU/L

- Free T4 normal

Question 25

Values of hormones in subclinical hyperthyreosis

Answer 25

- TSH <0.3mIU/L | - Free T3/T4 normal

Question 26

Values of hormones in hyperthyreodism

Answer 26

- TSH < 0.3mIU/L | - Free T3/T4 elevated

Question 27

How common is hypothyroidism?

Answer 27

Occurs in 3.8-4.6% of the population (10 times more common in women)

Question 28

Typical symptoms of hypothyroidism

Answer 28

- Slow HR, reduced CO, low voltage, dec. GFR, anemia - Weight gain, constipation - Myxoedema, hair loss, dry skin, carotenoderma - Tiredness, depression, psychosis, memory loss

Question 29

Primary causes of hypothyroidism (6)

Answer 29

1. Hashimoto's thyroiditis (autoimmune) 2. After treatment of hyperthryoidism 3. Inflammation 4. Iodine def. 5. Congenital (incomplete development, enzyme defects) 6. Drugs (amiodarone, lithium)

Question 30

Hashimoto's thyroiditis

Answer 30

Destruction of the thyroid gland by autoantibodies against thyroglobulin, thyroperoxidase, and other thyroid tissue components

Question 31

Postpartum thyroiditis

Answer 31

- Usually a transient phenomenon observed following pregnancy - Believed to result from modifications to the immune system necessary in pregnancy

Question 32

Subacute thyroiditis

Answer 32

Acute inflammatory disease probably caused by a virus

Question 33

Progression of subacute thyroiditis

Answer 33

Phase 1: Hyperthyroidism Phase 2: Euthyroid Phase 3: Hypothyroidism Phase 4: Euthyroid

Question 34

Subclinical hypothyroidism

Answer 34

Isolated elevated TSH level, but normal T3/T4, symptoms may or may not be present

Question 35

Subclinical hypothyroidism: Prevalence

Answer 35

Worldwide 1-10%, highest rate in women above 60 yrs

Question 36

8 underlying causes of hyperthyroidism

Answer 36

1. Graves disease 2. Plummers disease 3. Marine-Lenhart syndrome 4. Subacute thyroiditis 5. Hashimoto thyroiditis hyperthyroid phase 6. Thyreotoxicosis Facilita 7. Trophoblastic disease 8. Struma ovarii

Question 37

Characteristic symptoms of Graves disease

Answer 37

Opthalmopathy (exophthalmus), dermopathy (pretibial myxedema)