Basic principles of endocrinology

Question 1

What are the different types of action performed by the endocrine system? (give examples)

Answer 1

• Paracrine=the hormone acts locally by diffusing from its source to target cells in the neighborhood. e.g histamine from mast cells
• Autocrine= acts on the same cell that produced it e.g interleukins
• Neurocrine= The influence of nerves on endocrine tissue. e.g neurotransmitter noradrenaline.
• Endocrine= the hormone is distributed in blood and binds to distant target cells e.g insulin
• Neuroendocrine=released by neurons and carried by blood or other bodily fluids and act on distant cells e.g dopamine inhibition of prolactin release

Question 2

What are the main characteristics of hormones?

Answer 2

• synthesised and secreted by specialised cells
• released into circulation
• exert effects on target cells distant from release site
• act slowly
• act either on one cell type ( eg GnRH) or many cells types (e.g oestrogen)

Question 3

What is the role of the endocrine system?

Answer 3

• maintains homeostasis
• responds to changes in the environment( food,stress etc)
• important role in control of: growth, development,puberty,sexual maturation

Question 4

Which hormones are derived from tyrosine?

Answer 4

• dopamine
• adrenaline
• thyroxine

Question 5

What are the different classes of hormones?

Answer 5

• Tyrosine derivatives
• Peptide hormones
• Glycoprotein hormones
• Steroid hormones
• Catecholamines

Question 6

Describe the structure of glycoprotein hormones

Answer 6

Alpha and Beta chains with carbohydrate
The alpha chain= species specific- common to all 4 glycoprotein hormones
The beta chain= hormone specific- responsible for specificity

Question 7

Give eg’s of glycoprotein hormones.

Answer 7

LH, FSH, hCG, TSH.

Question 8

How does GnRH control release of LH& FSH

Answer 8

• Pulsatile release of GnRH release LH and FSH

- Sustained release of GnRH inhibit LH& FSH

Question 9

What are the different types of hormone release?

Answer 9

• Pulsitile e.g GnRH pulse generator
• Circadian based on 24hour cycle e.g cortisol
• Diurnal synchronised to day/night cycle
• Infradian based on longer than 24hour cycle e.g menstrual cycle
• Seasonal e.g prolactin

Question 10

What use can radioimmunoassay ( RIA) have in endocrinology

Answer 10

We can use RIA to assess hormone levels. As the conc. of hormone increases, the amount of antibody bound decreases. We can also use enzyme-linked immunosorbant assay (ELISA)

Question 11

What is the function of oestrogen receptor alpha

Answer 11

Activates transcription

Question 12

What is the function of oestrogen receptor beta

Answer 12

Inhibits transcription

Question 13

Where are thyroid hormones stored

Answer 13

stored in colloid as part of thyroglobulin.