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Flashcards in Pituitary function and failure Deck (32)
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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 possible causes of increased hormone activity?

How is this treated?

Hypersecretion: primary (gland abnormal) or secondary (gland normal)

Decreased plasma protein binding

Decreased removal from blood


Treatment: tumour removal, inhibiting drugs 


Define growth?

Net synthesis of proteins

Lengthening of long bones

Increased size and number of cells in soft tissues 


Describe the requirements for growth?

Growth hormone/somatotropin

Genetic determination

Adequate diet

No chronic disease or stressful environment 

Normal mix of growth-influencing hormones


What determines size at birth?


Environmental factors

Maternal nutrition 

Maternal health in general 


How does birth weight relate to disease later in life?

Small birth weight = adult disease 


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 


Describe what happens during the pubertal growth spurt?

Lengthening of long bones > height increase

Testosterone and oestorgen > sexual characteristics 


Describe the effects of growth hormone?

Metabolic effects: increase blood fatty acids and glucose

Soft tissues and skeleton: hyperplasia and hypertrophy, increase protein synthesis

Increase IGF production from liver 


Describe the half life of GH?

Short: 18 minutes 


Describe the factors affecting GH release?

Circadian rhythm of tonic release

Influenced by circulating nutrients, stress and other hormones 


What is somatomedin synthesis stimulated by?

Where are somatomedins produced?


(GH does not act directly on target tissues) 

Produced in liver 


What is somatostatin?

Growth hormone inhibitng hormone


Describe the hormones and paracrines required for tissue and bone growth?

GH and IGFs > protein and cell division

TH (permissive role)

Insulin > supports tissue growth

Oestrogen > closes epiphyseal plates

Calcium > bone growth 


Describe the effects of GH deficiency?

How can this be treated?

Dwarfism: decreased GH as child

Laron Dwarfism: GH receptors unresponsive

Adult onset: few effects 


If GH deficient, can treat with genetically engineered GH