Pituitary Gland

Question 1

What is a Peptide Hormone?

Answer 1

Synthesised as prohormones requiring more processing to activate.
Receptor : membrane receptors

Question 2

What is a Steroid Hormone?

Answer 2

Synthesised from cholesterol

Receptor: bind to intracellular targets ( travel through blood with protein )

Question 3

Peptide Hormone Storage?

Answer 3

Stored in vesicles ( regulatory secretion )

Question 4

Steroid Hormone storage?

Answer 4

Released immediately and not stored ( constitutive secretion )

Question 5

Where does the Pituitary gland sit and what is above it?

Answer 5

Part of sphenoid bone : Sella turcica

Above is Optic chiasm and Hypothalamus

Question 6

The Anterior pituitary has to be told what to do by the hypothalamus by neurones. What neurones?

Answer 6

Hypothalamic Parvocellular neurones:

Short neurones which terminate on median eminence
Release hypothalamic factors into capillary plexus in median eminence

Factors get into capillary because they are leaky and carried down by portal circulation to A-pituitary

Question 7

What five types of cells make up the anterior pituitary?

Answer 7

Samototrophs
Lactotrophs
Corticotrophs
Thyrothrophs
Gonadotrophs

( these cells make the ANTERIOR pituitary distinct from hypothalamus )

Cells regulated by the hypothalamic factors

Question 8

Hypothalamo-pituitary portal system 4 steps using Thyroxine hormone release example

Answer 8

Hypothalamis –> A Pituitary –. thyroid gland

1 - Axon terminals of hypothalamic neurosecretory cells release Thyrotrophin Releasing Hormone - TRH into Hypothalamo-hypophysial portal system

2 - TRH travels in the portal to A-pituitary

3 - TRH stimulates the release of Thyroid Stimulating Hormone from A-pituitary thyrotrophs

4 - TSH leaves the gland via the blood to travel to the thyroid gland to stimulate Thyroid hormone release - Thyroxine

Question 9

What hormones are made from each of the anterior pituitary cells?

Answer 9

S - growth hormone 
L - Prolactin
T - Thyroid stimulating hormone
G - LH + FSH
C - Adrenocorticotrophic hormone

Question 10

What is special about the growth hormone?

Answer 10

Growth Hormone releasing hormone ( on switch )
Somatostatin ( off switch )

Only hormone which can be turned on and off

Question 11

Which A-Pituitary Hormone(s) has an inhibited control?

Answer 11

Prolactin = inhibited by Dopamine

Question 12

Which A-pituitary Hormone(s) has releasing control ?

Answer 12

• TSH = thyrotrophin releasing hormone
• LH/FH = Gonadotrophin releasing hormone
• ACTH, corticotrophin = corticotrophin releasing hormone

Question 13

Where do each of the A-pituitary hormones target?

Answer 13

Growth H- liver/ body tissue
Prolactin - Lactating breasts
Thyrotrophin - Thyroid
Gonadotrophins - testes/ovaries
Adrenocorticotrophic hormone - Adrenal Cortex

Question 14

Why may Px with problem with pituitary gland not have hormonal problems?

Answer 14

Nearby structures may be affected:

e.g. bitemporal hemionopia ( because of pituitary tumour squashing optic chiasm - where medial retinae cross )

Question 15

What is the role of the A-pituitary in milk production?

What does mechanical stimulation of the nipple cause?

Answer 15

Activates afferent pathways ascending to hypothalamus inhibiting dopamine release

∴ Less inhibition of A-pituitary Lactotrophs

Increased plasma prolactin = milk secretion in mammary glands

( regulated by prolactin via dopamine ) .

Question 16

What 2 different ways does growth hormone exert growth?

Answer 16

Directly to receptors on muscle, bone etc

Indirectly to liver receptors. this stimulates IGF 1 production which travels to muscle, bone IGF 1 receptors

Question 17

What causes gigantism?

Answer 17

A pituitary tumour makes too much growth hormone - growth in height
ONLY happens before puberty is finished

Question 18

What is Acromegaly and what are its characteristics?

Answer 18

Excess growth hormone ( after puberty )

Coarsening of facial features
( Macroglossia, Prominent nose )
Prognathism
Increased hand/feet size
Sweatiness
Headache

NO increased height

Question 19

What are the Posterior pituitary hormones?

Answer 19

Two hormones:

Arginine vasopressin ( Anti-diuretic hormone )

Oxytocin

Question 20

How is the Posterior pituitary different to anterior?

Answer 20

Anatomically continuous with hypothalamus : neuronal tissue no endocrine tissue

Question 21

What are the Hypothalamic magnocellular neurons?

Answer 21

Long neurones - originate in supraoptic (AVP) and paraventricular (oxytocin) nuclei

Nuceli –> Stalk –> P-pituitary

Question 22

What are the roles of ADH?

Answer 22

stimulation of water reabsorption in renal collecting duct = concentrated urine

Vasoconstrictor - V1 receptor
Stimulates ACTH release from A-pituitary

Question 23

How does AVP concentrate urine?

AVP binds to ( a ) causing a cascade of ( b ) –> Adenylate cyclase –> ( c ) –> protein kinase A –> ( d ) = reabsorbs water

Answer 23

fill in gaps

a - V2 receptor
b - G proteins
c - cAMP
d - Aquaporins

Question 24

What are the physiological actions of oxytocin?

Answer 24

Contraction for Delivery of baby : When time for delivery Myometrial cells in uterus contract due to oxytocin

Contraction for Milk ejection :
Myoepithelial cells contract due to oxytocin

Question 25

Describe the 4 step Neuroendocrine milk ejection reflex arc?

Answer 25

Stimulation of nipple activates afferent pathways ascending to hypothalamus

Stimulate oxytocin releasing neurones

Oxytocin released into plasma = milk ejection increases