Hormone transport and kinetics

Question 1

Give examples of water soluble and lipid soluble hormones

Answer 1

Water= catecholamines e.g. epinephrine (adrenaline)
Lipid = cortisol and thyroid hormones

Question 2

List some lipid soluble binding proteins

Answer 2

• Can be either specific or non specific
• Specific= Cortisol binding protein/ Vit D globulin/ Thyroid binding globulin
• Non specific= albumin

Question 3

What is the impact to hormone transport if the liver is damaged?

Answer 3

As transport proteins are produced/ degraded in the liver, if the liver is damaged it can result in a lack of transport protein hence reduced hormone transport.

Question 4

Is the majority of hormone bond or free?

Answer 4

Majority is bound (remember active hormone= a free hormone)

Question 5

What do transport proteins function as?

Answer 5

• A hormone reservoir (remember majority of hormone is bound)
• Hormone buffers (they can bind to a surge of hormone to help inactivate it and reduce effects)
• Helps the kidney recycle hormones thus reducing loss

Question 6

How do transport proteins help the kidney recycle hormones?

Answer 6

As they are bound to hormones it reduced the chances of the hormone being filtered out at the glomeruli- Whereas free hormones are lost

Question 7

How is the plasma concentration of a hormone determined?

Answer 7

By how fast it is secreted AND how fast it is eliminated (from the blood)

Question 8

What are the elimination mechanisms regarding hormones?

Answer 8

• Enzymatic degradation= both the hormone and the receptor are degraded
• Can be eliminated within target cell AFTER binding
• Via the liver and kidney due to the P450 pathway

Question 9

Describe the elimination of T3 within the body

Answer 9

• Bound hormone as it is a lipid soluble hormone
• Bound hormones are resistant to degradation inside the cell
• It is EITHER converted to t£ and enters cell to alter gene expression. OR it is converted into water soluble compounds by the liver and excreted in the urine

Question 10

Describe the effects of thyroxine on different tissues

Answer 10

• Thyroxine acts to increase cellular metabolism
• Most stimulated tissues= heart/ gastric mucosa
• Least stimulated= skeletal muscle

Question 11

What is the problem with steroid withdrawal?

Answer 11

-If an animal has been on a long course of steroids and is withdrawn suddenly; the body has been measuring amount of steroid and feeding back that no more is needed= adrenal gland atrophies. So is no longer able to make its sufficient levels of steroid on its own. Animal goes into crisis when withdrawn suddenly.

Question 12

Describe RIA

Answer 12

Radio immuno assay: it is a diagnostic test and is highly sensitive= the known conc of hormone/ antigen is labelled. Once the unknown hormone is added it competes and knck the labelled hormone off. You can therefore measure the concentration of the unknown by how many labelled have been displaced.

Question 13

Regarding hormones, what does half life mean?

Answer 13

The time taken for the blood conc to reduce by 50%

Question 14

What hormones do the 4 organ-endocrine glands produce?

Answer 14

• Heart= ANP
• Intestine= Cholecystokinin and gastrin
• Kidney= 1,25 dihydroxycholecalciferol (active D3- regulates Ca2+) and EPO
• Placenta= chorionic gonadotrophins

Question 15

Define a hormone

Answer 15

Convey information from endocrine cells to hormones