Endocrinology

Question 1

Endocrine

Answer 1

Secretes hormone into a blood vessel

Question 2

Pancrine

Answer 2

Secretes local hormones

Question 3

Autocrine

Answer 3

Hormones act on same cell

Question 4

Neuroendocrine

Answer 4

Neuron axon terminates to bloodstream

Question 5

Trophic

Answer 5

Stimulates secretion of another hormone

Question 6

Chemical nature of hormones

Answer 6

1. Proteins. polypeptides
2. Glycoproteins e.g. LH, FSH
3. Derivatives of a.a. tyrosine e.g. adrenaline
4. Steroids derived from cholesterol
5. Lipid-derived molecules e.g. prostaglandins -> lipohphilic (on demand)

Question 7

Transport of hormones in blood

Answer 7

1. Peptide and proteins float in free form (hydrophilic)
2. Steroid and thyroid are transported into blood bound to serum proteins e,g, thyroxine binding proteins (hydrophobic) -> globulins are specific

Question 8

Only free circulating hormone is ____

Answer 8

Active, remainder acts as a resevoir so hormone levels can be altered by changing levels of binding proteins

Question 9

How do hormones work?

Answer 9

Most hydrophilic act on c.s. but steroid and thyroid have receptors in the nucleus

Question 10

Tyrosine phosphorylation as a single transduction event

Answer 10

1. Receptors for insulin + DDGF = TK so tyrosine phosphorylation
2. GH + prolactin receptors -> single membrane spanning proteins + their mode of signalling is by activation of signal transducers + transcription

Question 11

Steroid hormones + thyroid hormones are lipid- soluble so ..

Answer 11

1. Circulate in the blood bound to globulins
2. Unbound hormones enters the blood and bind to a receptors in the nucleus
3. Complex binds to DNA

Question 12

Difference between hydrophilic and hydrophobic hormones

Answer 12

1. Hydrophilic -> vesicle -> controlled at level of synthesis and secretion
2. Hydrophobic -> freely pass -> direct proportional rate of secretion and synthesis

Question 13

Hydrophobic hormone structure and example

Answer 13

N-linked/ O-linked + carbohydrate chains

1. Catecholamines -> numerous polar hydroxyl groups
2. Prostaglandins -> carboxylic acid group

Question 14

Hydrophilic hormone structure

Answer 14

Often have cyclic carbon structures which may be derivatives of cholesterol , tyrosine or vit A + D

Question 15

Hypothalamo-pituitary -gonadal axis

Answer 15

GnRH -> LH -> Gonadal steroids -> germ cell maturation

• Gonadal steroids inhibits LH + GnRH
• LH inhibits GnRH

Question 16

Hypothalamo-pituitary-adrenal axis

Answer 16

CRH- ACTH - Cortiso (+DHEA) -> glucose

Question 17

Hypothalamo-pituitary-thyroid axis

Answer 17

TRH- TSH - thyroid hormones -> metabolism

Question 18

Somatorophic axis

Answer 18

GHRH - GH - IGF-1 -> growth

Question 19

Failure of negative feedback in these systems leads to :

Answer 19

1. Defects in synthesis/ secretion of C
2. Defects in cellular response to C
3. Ectopic production of endocrine stimulus to production of C

Question 20

Oxytocin

Answer 20

Posterior pituitary hormone

Question 21

Effects of oxytocin

Answer 21

Stimulates contraction of myometrium -> passage of infant across cervix leads to distension of vaginal walls -> further secretion of oxytocin
+ lobulo-alveolar breast ducts

Question 22

Control of rate of secretion only

Answer 22

applicable to hydrophilic hormones whereas hepatic metabolism more imp. for clearance of hydrophobic hormones