Pituitary function and failure Flashcards
Describe the two components of the pituitary?
Include their origins and link to hypothalamus.
Posterior pituitary (neurohypophysis): derived from outgrowth of brain, neural tissue, neural link to hypothalamus
Anterior pituitary (adenohypophysis): derived from glanualr epithelial tissue, ectodermal cells, vascular link to hypothalamus
Describe the location of the pituitary gland?
Deep in base of brain
Sitting in sella turcica (sphenoid bone)
Describe the synthesis, storage and release of posterior pituitary hormones?
Hormone synthesised and packaged in cell body of neuron in hypothalamus > vesicles transported down neuron > vesicles stored in posterior pituitary > hormones released into blood
Where are posterior pituitary hormones synthesised and stored?
Synthesised in hypothalamus
Stored in posterior pituitary
List the major posterior pituitary hormones and their functions?
Vasopressin/ADH: increase collecting duct permeability and decrease urine volume
Oxytocin: milk ejection from breasts and uterine contraction
Describe the synthesis, strorage and release of anterior pituitary hormones?
Neurons synthesising trophic hormones release them into capillaries of portal system > portal vessels carry trophic hormones directly to anterior pituitary > endocrine cells release hormones into second set of capillaries > released to body
List the major anterior pituitary hormones, and the tissues they act on?
Prolactin > mammary glands
GH > musculoskeletal system
TSH > thyroid gland
ACTH > adrenal cortex
Gonadotropins (LH and FSH) > gonads
How is the hypothalamus connected to the anterior pituitary?
Portal vascular system / hypothalamic-hypophyseal portal system
Not connected to wider circulation
What type of hormones are hypothalmic hormones?
Most are releasing hormones
Describe the cell types in the anterior pituitary which are target cells for the hypothalamic hormones?
CRH > corticotroph
TRH > thyrotroph
GnRH > gonadotroph
GHRH > somatotroph
somatostatin (GHIH) > somatotroph
PRF > mammotroph
PIH > mammotroph
Why are there two levels of feedback present in the hypothalamic-pituitary axis?
i.e. final hormone feeds back to anterior pituitary and hypothalamus
Allows for fine control and regulation of hormone levels
Describe the two types of feedback present in the hypothalmic-pituitary axis?
Long loop feedback: final peripheral hormone feeds back to anterior pituitary and hypothalmus
Short loop feedback: pituitary hormone feeds back to hypothalamus
Describe the pathway for the release of GH?
What are somatomedins?
IGFs produced by the liver
Describe the possible causes of decreased hormone activity?
How is this treated?
Hyposecretion: primary (gland abnormal) or secondary (gland normal)
Increased removal from blood
Abnormal tissue response: lack of receptors or enzymes
Treatment: hormone administration
Describe the growth that occurs after birth?
Postnatal growth spurt: first 2 years
2yo to adolescence: linear gorwth rate declines
Pubertal growth spurt
Describe the effect of illness on child growth?
Can this be reversed?
Illness stunts child growth
If normal health is restored, can get period of catch up growth
What is somatomedin synthesis stimulated by?
Where are somatomedins produced?
GH
(GH does not act directly on target tissues)
Produced in liver
What is somatostatin?
Growth hormone inhibitng hormone
