Physiology Thyroid Book

Question 1

How is iodide converted to iodine

Answer 1

Thyroid peroxidase

Question 2

Process of making thyroid hormones

Answer 2

Iodide is absorbed from plasma by pump
Converted to iodine by TPO
Secreted into colloid where it is added to tyrosine by enzyme iodinate
These bind to protein- thyroglobulin
TSH causes them to be released back into thyroid follicular cell and released by proteolysis

Question 3

Composition of thyroid hormones in blood

Answer 3

99% bound to TBP and albumin
T4 higher conc

Question 4

Effects of thyroid hormones on body

Answer 4

Increase isotropic effect on heart
Increase protein breakdown
Increase carb absorption
Lipolysis

Question 5

3 hormones produced by thyroid

Answer 5

Tetra- principle hormone
Tri- shorter duration but more potent
Calcitonin- parafollicullar C cells

Question 6

Where does PTH act

Answer 6

Bone- resorption
DCT- reabsorption of Ca
PCT- excretion of PO4
Vit D formation

Question 7

Overall net effect of hyperparathyroidism on Ca exrection

Answer 7

Net excreten despite absorption in DCT due to overwhelmed

Question 8

Effect of thyroid hormone on PVR

Answer 8

Decrease due to raise in temp

Question 9

Effect of thyroid hormones on cholesterol

Answer 9

Increase LDL receptors- increased removal of cholesterol from circulation

Question 10

Where are thyroid receptors found

Answer 10

Intranuclear hormones
Which bind to DNA via zinc fingers

Question 11

Types of thyroid receptors

Answer 11

TRB2- brain
TRa2, TRB1- widely distributed in Body
T3 unable to bind to a2

Question 12

Factors inhibiting osteoclasts

Answer 12

Calcitonin, oestrogen, PGE2

Question 13

What inhibits osteoblasts

Answer 13

Corticosteroids

Question 14

How PTH causes action in cells

Answer 14

Binds to surface receptors
Increase cAMP

Question 15

What cell is PTH released from

Answer 15

Chief cells

Question 16

Biochemistry of primary HPTH

Answer 16

High PTH
High Ca
Low PO4
Normal VitD
Raised urinary Ca

Question 17

Biochemistry of secondary HPTH

Answer 17

Low Ca
High PTH
High PO4

Causes- renal failure and vid D def

Renal failure- high phosphate which inhibits Vid d synthesis
Or Failure of 1a production

Question 18

Biochemistry of tertiary HPTH

Answer 18

High Ca
High PTH
High PO3- due to original renal failure
Developed after longstanding secondary HPTH

Question 19

Effects of calcitonin

Answer 19

Decrease bone resorption
Increase renal exretion of Ca and PO4

Question 20

Factors increasing calcitonin secretion

Answer 20

B adrenergic agonists
Glucagon
Gastrin
CCK
Oestrogens

High Ca

Question 21

Sx of hypocalcaemia

Answer 21

Tetany
Numbness
Prolonged QT

Chvostek- contraction of facial muscle when tapping on angle of jaw

Trousseau- wrist flexion and fingers drawn together in extension when BP cuff inflated

Question 22

Why does low Ca cause tetany

Answer 22

Low Ca increases neuronal permeability

Question 23

Hypercalcaemia sx

Answer 23

Constipation
Increases uriantion

Bone pain
Abdo pain
Mental health
Renal stones

Question 24

Causes of high Ca

Answer 24

Primary HPTH
Malignancy- breast, lung, SCC
Multiple myeloma
Renal failure
Thiazide use

Question 25

Effect of surgery or trauma on thyroid hormones

Answer 25

Decrease for a few days

Question 26

Sick euthyroid syndrome biochemistry

Answer 26

Low T3
Normal T4 and TSH- may be high

Question 27

Medications that effect levothyroixine absorption

Answer 27

Iron
Ca
PPI
Statins
Oestrogens