endocrine axis basics

Question 1

definition of autocrine, endocrine and paracrine

Answer 1

• autocrine: cell produced substance affecting only cell produced
• paracrine: cell produced substance that affects in the vicinity of the cell
• endocrine: cell produced substance ie hormones that can affect hormones far away

Question 2

what hormones does the pituitary produce

anterior 6
posterior 2

Answer 2

ANTERIOR pituitary:
1. adreno-cortico trophin hormone
2. luteinsing hormone
3. follicle stimulating hormone
4. growth hormone
5. prolactin
6. thyroid stimulating hormone
POSTERIOR
1. AVP/ADH: arginine vasopressin
2. Oxytocin

Question 3

what hormones does the thyroid 2 and the parathyroid 1 produce

Answer 3

thyroid: thyroxine and calcitonin
parathyroid: PTH

Question 4

what does the adrenal cortex and the adrenal medulla produce

Answer 4

adrenal cortex: cortisol, aldosterone, dhea

adrenal medulla: adrenaline and noradrenaline

Question 5

3 types of hormones

Answer 5

1. peptides: gene products eg GH, insulin- water soluble so circulate in blood
2. amines: transport on plasma proteins-modified AAs, adrenaline, nora
3. steroids: transport on plasma carrier proteins form cholesterol, lipid soluble bind to intracellular receptors: oestrogen, androgen, glucocorticoids

Question 6

how do the receptors for peptides and amines work

Answer 6

• peptides and amines: surface receptors, second messengers, multiple cellular effects
• activate GPCR g protein coupled receptors

Question 7

how do the receptors for steroids and thyroid hormones 4 stages

Answer 7

1. steroid hormones transport in blood bound to carrier protein
2. difuse through plasma membrane and bind to inactive steroid receptors
3. activated hormone receptor complex enters nucleus to become a transcription factor and binds on dna
4. activates gene transcription in nucleus promoting protein synthesis
   - steroids and thyroid hormones:bind to intracellular nuclear receptors, via transcription/translation, many target genes

Question 8

difference between exocrine and endocrine glands

Answer 8

endocrine glands: don’t have glands, secrete products directly
exocrine glands: secrete their products into ducts and carry to a specific location

Question 9

describe the pancreas exo and endocrine functions

Answer 9

pancreas

endocrine: islets of langerhans secrete insulin, glucagon, somatostatin, pancreatic polypeptide
exocrine: pancreatic fluid with digestive enzymes

Question 10

what does intracrine mean

Answer 10

intracellular activation of prohormones eg sex steroids

Question 11

draw the hypothalamic pituitary axis

Answer 11

1.hypothalamus
promotes release of 
2. anterior pituitary hormone
which act on a distant 3.endocrine gland
to stimulate an end organ response 
4. target tissue, physiological response

Question 12

definition of homeostasis

Answer 12

conditions in the body are controlled to provide a constant internal stable environment

Question 13

difference between posterior and anterior pituitary

Answer 13

posterior: an extension of the CNS, nerve fibres in the pituitary stalk
anterior: originates from neural ectoderm, blood supply from median eminence

Question 14

blood supply and drainage of the pituitary stalk

Answer 14

1. hypothalamic median eminence: superior hypophysial arteries
2. hypophyseal portal system

Question 15

blood supply to the anterior pituitary and posterior pituitary

Answer 15

anterior= arterial from median eminence venous blood via the hypophyseal portal system
posterior: arterial blood from the inferior hypophysial arteries

Question 16

stages of production or inhibition of 
growth hormone
prolactin
fsh and lh
acth
fsh

Answer 16

1. produces growth hormone =somatotrophs= ghrh=arcuate nucleus
2. inhibits prolactin lactotrophs = dopamine= arcuate nucleus
3. produces fsh and lh= gonadotrophs =gnrh= preoptic nucleus
4. produces acth= corticotrophs= crh= paraventricular
5. tsh= thyrotrophs= trh= paraventricular

Question 17

what does the periventricular nucleus produce and what does it do

Answer 17

produces somatostatin which inhibis thyrotrops and somatotrophs

Question 18

what nucleus produces avp and oxytocin and where

Answer 18

IN hypothalamus supraoptic nucleus that then travels to posterior pituitary via median eminence blood supply

Question 19

what is the synacthen tes and what is it used for

Answer 19

used to test insufficiency
given as a low dose and high dose of acth to test response
1. in primary cortisol isufficiency or addison’s disease both cortisol and aldoesterone low as cant respond to acth
2. could also test if secondary as if mild then the adrenal glands may still respond to acth because the adrenal glands have not atrophied yet but to tell diff best to use crh test

Question 20

what is the crh test used for

Answer 20

tell if primary or secondary adrenal insufficiency as in primary would still produce acth but no cortisol and in secondary would be no acth

Question 21

what is the overnight dexamethasone test

Answer 21

synthetic glucocorticoid provides negative feedback to suppress pituitary acth secretion and cortisol

1. low dose suppress pituitary acth and cortisol in normal individuals but not form pituitary adenima
2. high dose would part inhibit acth secretion from a pituitary adenoma but not from an ectopic acth producing tumour or a cortisol producing adrenal adenoma

Question 22

regulators of GnRH

Answer 22

oestrogen
progesterone
androgen
prolactin
inhibin

Question 23

regulator of TRH

Answer 23

t3

Question 24

lactation pathway

Answer 24

oestrogen and stress
dopamine
prolactin (trh acts on)
breast
lactation

Question 25

growth hormone pathway

Answer 25

IGF1
somatostatin
GH
liver
IGF1, IGFBP3
Growth

Question 26

stress pathway

Answer 26

circadian rhythm, stress,cortisol
crh
acth
adrenal cortex
cortisol and androgen
stress

Question 27

what cells does the islet of langerhans have and what do they produce

Answer 27

alpha cells=glucagon
betal cells=insulin
delta cells= somatostatin
f cells= pancreatic polypeptide