Endocrinology

Question 1

Define endocrine gland

Answer 1

A gland that makes and secretes hormones into the blood stream through which they travel to distant targets

Question 2

Define exocrine

Answer 2

A gland that makes and secretes hormones through ducts opening onto an epithelium rather than directly into the blood.

Question 3

Define paracrine

Answer 3

Substance secreted and acting on adjacent cells. (e.g. neurotransmitters)

Question 4

Define autocrine

Answer 4

Substances secreted by cell and act on the receptors on the surface of the same cell.

Question 5

Define hormone

Answer 5

A chemical substance produced by cells and released especially into the blood and having a specific effect on cells or organs usually at a distance from the place of origin.

Question 6

Define endocrine

Answer 6

Hormones secreted and act on distant targets

Question 7

Define cytokines

Answer 7

Peptides with autocrine, paracrine and endocrine functions

Question 8

What are the main endocrine organs?

Answer 8

Hypothalamus
Pituitary
Thyroid
Thymus
Pancreas
Adrenal glands
Kidneys
Ovaries
Uterus
Testes

Question 9

What other tissues have endocrine functions?

Answer 9

Heart
Gut
Liver
Adipocytes
Placenta

Question 10

What are the major molecular types of hormones?

Answer 10

Proteins
Modified amino acids
Steroids

Question 11

Name examples of amino acid derived hormones

Answer 11

Catecholamines and serotonin (single amino acids)
Thyroid hormones (dipeptides)
TRH, vasopression, somatostatin (small peptides)
Insulin and PTH (intermediate peptides)
Gonadotrophs (complex polypeptides)

Question 12

Name hormones derived from lipid precursors

Answer 12

Steroids (cortisol, sex steroids, vitamin D)

Prostaglandins

Question 13

Describe the process of protein and peptide hormone synthesis

Answer 13

1) Gene transcription
2) mRNA to rER
3) Translation on rER
4) Post-translational processing
5) Packaging into secretory vesicles in golgi apparatus
6) Exocytosis

Question 14

Describe the process of steroid hormone synthesis

Answer 14

1) hydrolysis of esters and release of cholesterol (or by direct uptake of cholesterol)
2) Cholesterol modified to prenenolone in mitochondrion
3) Processing in sER
4) Diffusion through cell membrane (hydrophobic)

Question 15

How are hormones transported in the blood?

Answer 15

Hydrophilic (water soluble- dissolve in water
Hydrophobic (fat soluble):
-Transported bound to plasma binding proteins (inactive when bound, protected, acts as reservoir)

Question 16

Describe the mechanism of action of water soluble hormones

Answer 16

Bind to G-protein coupled receptors:
acts on either adenylate cyclase to activate cAMP to activate protein kinases; or activates phospholipase C which activates IP3 which stimulates Ca2+ release from ER which further signals downstream events.

Tyrosine-kinase receptor system:
Receptor binding causes phosphorylation and activation of receptors which activates nearby proteins which causes a signalling cascade (e.g. insulin)

Question 17

Describe the mechanism of action of fat soluble hormones

Answer 17

Bind to intracellular receptors:
Intracellular receptors take hormone to nucleus and DNA where transcription produces mRNA which is translated by ribosomes on rER and new proteins are produced.

Or cell surface receptors (same action as water soluble receptors)

Question 18

Give an example of postive feedback

Answer 18

Release of egg from ovaries (oestrogen causing surge of luteinising hormone)

Question 19

Define tropic hormone

Answer 19

Affects other endocrine glands to produce a response

Question 20

Define trophic hormone

Answer 20

Affects growth and development directly

Question 21

What are the actions of glucocorticoids?

Answer 21

Decrease muscle mass
Modulate emotions and wakefulness
Increase glomerular filtration
Initiate maturation of foetus
Increase bone resorption and reduce bone function
Decrease inflammatory and immune response
Decrease connective tissue

Question 22

What are the symptoms of excess glucocorticoid production? (Cushing’s syndrome)

Answer 22

Central weight gain
Depression, psychosis, insomniia
Amenorrhoea
Decreased libido
Bruising
Growth arrest
Polyuria/polydipsia

Question 23

What are the symptoms of underproduction of glucocorticoids?

Answer 23

e.g. Addison's disease (hypoadrenalism)
Weight loss
Anorexia
Weakness
Fever
Depression
Impotence
Amenorrhoea
Nausea/vomiting
Confusion
Back/abdo pain

Question 24

Define primary endocrine dysfunction

Answer 24

Excess effector hormone from an endocrine organ

Question 25

Define secondary endocrine dysfunction

Answer 25

Overstimulation of effector endocrine organ by excessive tropic hormone

Question 26

What are the roles of glucocorticoids?

Answer 26

Decrease bone function and increase resorption, decrease connective tissue, inhibit inflammator y and immune response, increase glomerular filtration, modulate emotional tone and wakefulness, decrease muscle mass.

Question 27

What are the effects of glucocorticoid excess?

Answer 27

Cushing’s syndrome

Central weight gain, depression, psychosis, insomnia

Question 28

What are the effects of underproduction of glucocorticoids?

Answer 28

Addison's disease (hypoadrenalism - reduced glucocorticoid and mineralocorticoid)
Weight loss/anorexia
Weakness
Fever
Depression
Impotence/amenorrhoea
Nausea/vomiting
Confusion
Back and abdo pain