endocrine axis basics Flashcards
definition of autocrine, endocrine and paracrine
- 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
what hormones does the pituitary produce
anterior 6
posterior 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
what hormones does the thyroid 2 and the parathyroid 1 produce
thyroid: thyroxine and calcitonin
parathyroid: PTH
what does the adrenal cortex and the adrenal medulla produce
adrenal cortex: cortisol, aldosterone, dhea
adrenal medulla: adrenaline and noradrenaline
3 types of hormones
- peptides: gene products eg GH, insulin- water soluble so circulate in blood
- amines: transport on plasma proteins-modified AAs, adrenaline, nora
- steroids: transport on plasma carrier proteins form cholesterol, lipid soluble bind to intracellular receptors: oestrogen, androgen, glucocorticoids
how do the receptors for peptides and amines work
- peptides and amines: surface receptors, second messengers, multiple cellular effects
- activate GPCR g protein coupled receptors
how do the receptors for steroids and thyroid hormones 4 stages
- steroid hormones transport in blood bound to carrier protein
- difuse through plasma membrane and bind to inactive steroid receptors
- activated hormone receptor complex enters nucleus to become a transcription factor and binds on dna
- activates gene transcription in nucleus promoting protein synthesis
- steroids and thyroid hormones:bind to intracellular nuclear receptors, via transcription/translation, many target genes
difference between exocrine and endocrine glands
endocrine glands: don’t have glands, secrete products directly
exocrine glands: secrete their products into ducts and carry to a specific location
describe the pancreas exo and endocrine functions
pancreas
endocrine: islets of langerhans secrete insulin, glucagon, somatostatin, pancreatic polypeptide
exocrine: pancreatic fluid with digestive enzymes
what does intracrine mean
intracellular activation of prohormones eg sex steroids
draw the hypothalamic pituitary axis
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
definition of homeostasis
conditions in the body are controlled to provide a constant internal stable environment
difference between posterior and anterior pituitary
posterior: an extension of the CNS, nerve fibres in the pituitary stalk
anterior: originates from neural ectoderm, blood supply from median eminence
blood supply and drainage of the pituitary stalk
- hypothalamic median eminence: superior hypophysial arteries
- hypophyseal portal system
blood supply to the anterior pituitary and posterior pituitary
anterior= arterial from median eminence venous blood via the hypophyseal portal system
posterior: arterial blood from the inferior hypophysial arteries
stages of production or inhibition of growth hormone prolactin fsh and lh acth fsh
- produces growth hormone =somatotrophs= ghrh=arcuate nucleus
- inhibits prolactin lactotrophs = dopamine= arcuate nucleus
- produces fsh and lh= gonadotrophs =gnrh= preoptic nucleus
- produces acth= corticotrophs= crh= paraventricular
- tsh= thyrotrophs= trh= paraventricular
what does the periventricular nucleus produce and what does it do
produces somatostatin which inhibis thyrotrops and somatotrophs
what nucleus produces avp and oxytocin and where
IN hypothalamus supraoptic nucleus that then travels to posterior pituitary via median eminence blood supply
what is the synacthen tes and what is it used for
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
what is the crh test used for
tell if primary or secondary adrenal insufficiency as in primary would still produce acth but no cortisol and in secondary would be no acth
what is the overnight dexamethasone test
synthetic glucocorticoid provides negative feedback to suppress pituitary acth secretion and cortisol
- low dose suppress pituitary acth and cortisol in normal individuals but not form pituitary adenima
- 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
regulators of GnRH
oestrogen progesterone androgen prolactin inhibin
regulator of TRH
t3
lactation pathway
oestrogen and stress dopamine prolactin (trh acts on) breast lactation
growth hormone pathway
IGF1 somatostatin GH liver IGF1, IGFBP3 Growth
stress pathway
circadian rhythm, stress,cortisol crh acth adrenal cortex cortisol and androgen stress
what cells does the islet of langerhans have and what do they produce
alpha cells=glucagon
betal cells=insulin
delta cells= somatostatin
f cells= pancreatic polypeptide
