Lecture 28: Physiology of the hypothalamus and pituitary Flashcards Preview

1060 Human form and function > Lecture 28: Physiology of the hypothalamus and pituitary > Flashcards

Flashcards in Lecture 28: Physiology of the hypothalamus and pituitary Deck (20):

Hypothalamus and pituitary: anatomy 

the hypothalamus is an area on the base of the brain,

neurones send axons down from the hypothalamus

to form the posterior pituitary, a neuroendocrine organ that secretes the hormones oxytocin and vasopressin (antidiuretic hormone)



the posterior pituitary has a neuronal developmental origin as a down-growth from the diencephalon (part of the brain) 

the anterior pituitary is ectodermal in origin 

the anterior pituitary secretes
growth hormone (GH)
follicle stimulating hormone (FSH)

leutinising hormone (LH)

adrenocorticotrophic hormone (ACTH)

thyroid stimulating hormone (TSH)

prolactin (PL) 

neurones in the hypothalamus send axons to the
median eminence 

to control the release of hormones from the anterior pituitary 

hormones released from the anterior pituitary enter the venous drainage to reach their target tissues elsewhere in the body 


Hypothalamus and pituitary: summary 

the posterior pituitary is neuronal, releases oxytocin and vasopressin

the anterior pituitary is ectodermal, releases GH, FSH, LH, ACTH,TSH, PL

cells in the hypothalamus release peptide hormones (neurohormones) into the portal blood vessels

(at the median median eminence) which influence the release of hormones from the anterior pituitary 


Releasing hormones in the hypothalamus and pituitary ??

Releasing hormones

GHRH: growth hormone releasing hormone (GH)

CRH: corticotropin releasing hormone (ACTH)
TRH: thyrotropin-releasing hormone (TSH)

GnRH: gonadotropin releasing hormone (LH, FSH) 


Inhibiting hormones in the hypothalamus and pituitary==

Inhibiting hormones
SS: somatostatin (GH, TSH)

DA: dopamine (PL) 



Hypothalamus and pituitary:hormones and their actions 



Anterior pituitary hormones:FSH/LH 

what do they do ??

Luteinising and Follicle-Stimulating hormones

made in luteotrophs (gonadotrophs)

released by hypothalamic GnRH

control production of steroid hormones by ovary: oestrogen and progesterone

control production of steroid hormones by testis: testosterone

gonadal steroids control sexual differentiation, behaviour andfertility 


Anterior pituitary hormones:FSH/LH 

what happens if you have a loss of FSH/LH secretion ??

loss of function in children prevents puberty

calorie restriction in adults (anorexia, excessive exercise) causes loss of reproductive function 


nutritional status/ fat stores detected by hypothalamus 

reproductive cycle switched off via hypothalamus /pituitary 

administration of GnRH, FSH/LH can be used to manipulate reproduction 


Anterior pituitary hormones: GH 

Growth hormone

made in somatotrophs
released by hypothalamic GHRH
release inhibited by hypothalamic SS 

direct anabolic effect in many tissues

targets liver to produce somatomedins (IGFs)

somatomedins (aka insulin-like growth factors) stimulate growth in many tissues 


Anterior pituitary hormones: GH 

what happens when you lack it??

Lack of GH
short stature, treated by GH treatment 


Anterior pituitary hormones: GH 

What happens when you have tooo much of it??

Too much GH
giantism if secreted throughout growing period 

acromegaly if secreted after bones have fused - hands feet and jaws continue to grow 


over-secretion of GH in adult
usually due to a pituitary adenoma 


Anterior pituitary hormones: TSH 

made in thyrotrophs
released by hypothalamic TRH
acts on thyroid to generate triiodothyronine (T3) and thyroxine(T4)
T3 and T4 regulate growth and development by multiple actions 


Not enought TSH hormones?


Too much TSH??


Anterior pituitary hormones: PRL 


made in mammatrophs
release inhibited by hypothalamic dopamine
stimulates lactation in post-partum period
oversecretion leads to loss of reproductive function 


Too much Prolactin??


Anterior pituitary hormones: ACTH 

Adrenocorticotrophic hormone 

made in corticotrophs
released by hypothalamic CRH
controls steroid production by adrenal cortex
adrenal steroids regulate sodium balance, blood pressure, metabolism, responses to stress 


Too much adrenal steroids ?

(Cushings syndrome) 


Feedback control in hypothalamo-pituitary system 

multiple levels of control

negative (inhibitory) feedback on the hypothalamus to reduce the secretion of releasing hormone

negative feedback on anterior pituitary to reduce the secretion of pituitary hormone 


Feedback control in endocrine systems 


Feedback control in endocrine systems : growth hormone 

GH released from pituitary feeds back on hypothalamus to inhibit GHRH 

GH released from pituitary feeds back on pituitary to inhibit GHRH

IGF-1 released from liver by GH feeds back to inhibit GH release from pituitary

IGF-1 feeds back on hypothalamus to increase SS release (which inhibits GH release from pituitary)