hypothalamic pituitary hormones Flashcards
what is homeostasis?
the body trying to regulate itself
its about successful compensation and when there isn’t a balance then there is illness
explain the hypothalamus pituitary axis
the hypothalamus links the nervous system with the endocrine system
its involved in osmolality, temperature regulation, stress
there is an anterior and posterior pituitary gland that is associated with the hypothalamus
The hypothalamus produces peptide hormones that control production of pituitary hormones
the pituitary anterior lobe contains several discrete cell types
what are they and what do that produce?
the anterior pituitary lobe contains several cell types eg.
somatotrophs: growth hormone
gonadotroph: LH & FSH
Lactotroph: prolactin
Thyrotrophs: TSH
Corticotrophs: ACTH
explain the hypothalamic anterior pituitary / adrenal gland axis
The hypothalamus releases CRF which travels to the anterior pituitary gland which stimulates the production of ACTH
ACTH enters the systemic circulation and stimulates receptors found in the adrenal cortex that generate cAMP
ACTH regulates the secretion of:
cortisol
aldosterone
dhea
aldosterone regulates metabolism and adaption to stress
functions primarily on the kidney in maintaining sodium levels and blood volume
FSH axis
FSH primarily bind to receptors on sertolli cells
androgen binding protein binds to testosterone and maintains local high levels
aromatise converts testosterone to estradiol
Inhibins- inhibit FSH secretion by decreasing mrna
growth hormone axis
GHRF released from the hypothalamus which acts on anterior pituitary glands which release growth hormone from the somatotrophs which can act on the liver
growth hormone can be inhibited by decrease in cAMP levels caused by somatostatin
therefore somatostatin analogues are used in growth hormone excess disorders
GH works by met`; increasing lipolysis and increasing plasma glucose . growth promoting: increasing amino acid uptake and protein syntheses
JAK/STAT pathway
GH diseases
Dwarfism:
- deficiency in GH in childhood- disruption of GHRH secretion and release of GH
- pituitary tumour: treated by somatorelinanalogue like sermorelin
Gigantism:
- excess
- pituitary tumour
- treated with somatostatin analogues
- sandostatin
prolactin axis
secretion of prolactin by the anterior pituitary lobe which was stimulated by Prolactin releasing factor which can get inhibited by dopamine
Prolactin secretion increases during pregnancy for lactation, breast tissue development
prolactin diseases
prolactin excess may occur in males and females
hyperprolactaemia: caused by certain drugs and tumours
- decrease in sexual function
females: missing periods, random lactation
males: enlarged breasts, decrease libido decrease sperm production
dopamine antagonists: increase prolactin
dopamine agonists: treat prolactin excess
explain posterior pituitary hormone release
cell bodies reside in paraventricular and supraoptic nuclei of the hypothalamus extend its axons and the terminal ends up at the posterior pituitary gland
different to anterior: no releasing factors: hormone released via depolarisation and ca2+ influx inducing exocytosis
they are released directly into the system where they act on uterus and kidneys
ADH receptors and their effects
ADH is released from the posterior pituitary gland and acts on the kidneys
structurally similar to oxytocin however differs by 2 aa’s
function: contraction of smooth muscle and enhances water absorption so there’s small urine
ADH receptors
v1: presser effect acts on arterioles and GIT: PLC/IP3
V2: acts on kidneys: adenyl cyclase and Gs
v3: acts on adrenal cortex to control ACTH in a minor way: PLC/IP3
how is oxytocin released and what does it cause
oxytocin is a peptide hormone that differs from ADH by 2 aa’s
it is released from posterior pituitary gland where it binds to oxytocin receptors which medicate contraction and milk ejection
released in response to; elevated oestrogen levels
sensory stimuli or cervix and vagina
suckling of breasts
involved in positive feedback
oxytocin is inhibited by catecholamines and stress
destroyed if given orally therefore needs to be given nasally or IV
