Thyroid Physiology

Question 1

At what vertebral level is the thyrod gland found?

Answer 1

C5 - T1

Question 2

What supplies parasympathetic control to the thyroid gland?

Answer 2

Vagus nervee

Question 3

What is the arterial supply for the thyroid?

Answer 3

Superior and inferior branches of the thyroid arteries

( branch of the external carotid artery )

Question 4

What is this stucture called?

Answer 4

A Follicle

Question 5

What are the cells making up the ring called?

Answer 5

Follicular cells

Question 6

What is the middle of the ring called and what does it contain?

Answer 6

Collioid thyroglobulin

Question 7

What ingredient is required to make thyroid hormones?

Answer 7

Iodine

Question 8

Two DITs makes ….

Answer 8

T4

Question 9

One MIT and One DIT makes ____?

Answer 9

T3

Question 10

What percentage of thyroid hormone is thyroxine and what percentage is triiodothyronine ?

Answer 10

90% thyroxine T4

10% Triiodothyronine T3

Question 11

What thyroid hormone is more potent T3 or T4?

Answer 11

T3 is 4x more potent

Question 12

What plasma proteins do T3 and T4 bind to?

Answer 12

Thyroxine binding globulin 70%

Thyroxing binding prealbumin 20%

Albumin 5%

Question 13

What effects do thyroid hormones have on metabolic rate and thermogenesis?

Answer 13

Increase metabolic rate

Increases thermogenesis

Question 14

What effect do thyroid hormones have on sympathetic action?

Answer 14

Increases responsiveness to adrenaline and sympathetic neurotransmitters.

Question 15

What stimulates the thyroid and where does it come from ?

Answer 15

Thyroid stimulating hormone from the anterior pituritory gland

Question 16

What is graves disease?

Answer 16

Autoimmune disease where Thyroid stimulating immunoglobin acts like thyroid stimulating hormone leading to hyperthyroidsism

Question 17

What 3 hormones does thyroid gland tissue secrete?

Answer 17

Thyroxine (T4)

Tri-iodothyronine (T3)

Calcitonin

Question 18

What do the parathyroid glands secrete?

Answer 18

Parathyroid Hormone PTH

Question 19

What veins drain the thyroid gland?

Answer 19

Superior and middle thyoid vein into the internal jugular vein

Inferior thyroid vein into the brachiocephalic vein

Question 20

How are thyroid hormones regulated?

Answer 20

Thyrotrophin releasing hormone (TRH) from the hypothalmus stimulates the anterior pituitary to release thyroid stimulating hormone. (TSH)

Question 21

What a patient with an over active thyroid what would be the TSH T4 and T3 levels?

Answer 21

T4/T3 high

TSH low

Question 22

What would be the TSH T3 and T4 levels in a failing thyroid gland?

Answer 22

TSH high

T4/T3 low

Question 23

What would the TSH and T3/T4 values be in secondary hyperthyroidism?

Answer 23

TSH high

T3/T4 high

Question 24

What does Myxoedema mean?

Answer 24

Severe hypothyroidism

or

Skin disease associated with Graves

Question 25

What is Hashimoto's hyroiditis?

Answer 25

Autoimmune hypothyroidism

Question 26

What happens in autoimmune hypothyroidisim?

Answer 26

Autoimmune destruction of the thyroid gland resulting in reduced thyroid hormone production

Question 27

What is characterisitic of Hashimoto's thyroiditis?

Answer 27

Presence of Thyroid Peroxidase antibodies T-cell infiltrate and inflammation on microscopy

Question 28

What are the facial signs and symptoms of hypothyroidisim?

Answer 28

Coarse, sparse hair Periorbital puffiness Loss of outer eyebrows Peri-orbital puffiness

Question 29

What is the management plan for hypothyroidisim?

Answer 29

In young patients:- 50-100micrograms In elderly with ischeamic heart disease:- start at 25-50 micrograms

Question 30

What happens in Myxoedema coma?

Answer 30

extreme hypothyroidisim Type 2 respiratory failure Bradycardia, low voltage complexes, heart block, prolonged QT interval

Question 31

What happens to the menstral cycle in patients with (a) hyperthyroidisim (b) Hypothyroidisim

Answer 31

Hyperthyroidisim - Less frequent and lighter bleeding Hypothyroidisim - Heavier bleeds

Question 32

What are the three common causes of hyper-thyroidism?

Answer 32

Graves disease Nodular thyroid Thyroiditis

Question 33

What is the natural progression of graves disease?

Answer 33

after 18 months 50% will "burn out" 50% will relapse

Question 34

What is responsible for graves disease

Answer 34

Thyroid stimulaing immunoglobulin

Question 35

What is Thyroid storm?

Answer 35

Severe hyperthyroidisim resulting in respiratory and cardiac collapse

Question 36

How do you treat hyperthyroidism?

Answer 36

Carbimazole

Question 37

How do you treat hyperthyroidism in pegnancy?

Answer 37

Propylthiouracil

Question 38

What is De Quervains Thyroiditis?

Answer 38

Sub-Acute Thyroiditis

Question 39

What happens in sub-Acute thyroiditis?

Answer 39

T4 is high in early stage , low in late then is normal TSH componsates accordanly Can be triggered by viral infection ( Sore throat etc)