Pituitary Feedback And Disorders

Question 1

Pomc BD in both pars

Answer 1

To acth and b lipotropin
Only in PI does acth go to aMSH and CLIP
Blipo goes to BEND goes to met enkephalin

Question 2

aMSH

Answer 2

Stim prod and release of melanin by melanophores and cytes
Reg by dopamine
Has central effect in mammals
Signals in brain to reg appetite and sexual arousal

Question 3

Melanophores

Answer 3

Specialised skin cells in reptiles fish and amphib
Cont melanin granules that darken the skin when dispersed in the melanophore
Conc around nucleus skin lightens
Neuroendo reflex mech
Recs in retina cause colour change due to MSH (light background inhib MSH release causing lighter colour)

Question 4

Melanocytes

Answer 4

Specialised skin cells in mammals and birds
Transfer melanosomes (cont melanin) to skin and hair follicles and feathers
MSH treatment accel melanin synth causing darker skin

Question 5

Excess MSH

Answer 5

Pigment abnormality

Cushings has hyperpigmentation as incr acth (with consideravle MSh activity)

Question 6

Juvenile GH

Answer 6

Prom skel growth
Most key h for growth to adult size
Stable secr (burst at puberty)

Question 7

Adult GH

Answer 7

Prom m dev and bone maintenance
Secr through life
After pubertal burst, decline to stable level

Question 8

GH effects

Answer 8

Incr pro synth and decr gluc usage
Direct- incr fat metab, TG BD, suppress adupocyte uptake of circ lipid
Indirect- incr bone growth. Incr IGF1 secr by liver in resp to GH

Question 9

GH release

Answer 9

Secr conrtolled by GRH (synthed by neurones in arcuare nucleus of hypot and released from neurosecr terminals at median eminence)
Controlled by somatostatin (peptide synthed by neurosecr neurones in periventric nucleus) inhib factor for GH

Question 10

GH GRH and somatostatin storage and release

Answer 10

Stored in large dense core vesicles

Release by Ca dep exocytosis

Question 11

GH stim factors

Answer 11

Decr gluc
Decr FFA
Fasting
Puberty hs
Exercise
Stress 
Sleep (stage 3&4)
a adrenergic agonists
Arginine

Question 12

GH inhib factors

Answer 12

Incr gluc and FFA
Obesity
Senescence
GH
Pregnancy
Somatostatin
Somatomedins
B adrenergic agonists

Question 13

GH pulsatility

Answer 13

Peak every 2hr
Largest secr burst within 1hr of sleep
Largest pulses at stages 3&4 of sleep
More marked pulsatility in M - majn explan for diff growth rates

Question 14

GH release reg and feedback

Answer 14

Ghrelin secr by stomach act on somatotrophs to release GH directly and within hypot to stim GRH release
At pit GRH and ghrelin act indep to stim GH release via diff recs and IC signalling pathways
GH and IGF have -ve feedback in brain
GH acts directly on somatostatin neurones so must x BBB

Question 15

Dwarfism cause and symptoms

Answer 15

Decr GH or GRH or insens of recs (pre puberty)
Incr body fat
Decr m mass, bone density (incr fracture risk), insulin sensitivity
Impaired cardiac fx and glucose tolerance

Question 16

German shepherd dwarfism cause

Answer 16

Autosomal recssive cause hypoplasia of ant pit

Question 17

Giantism

Answer 17

Excess GH secr pre puberty

Most marked in limb and foot length

Question 18

Acromegaly cause

Answer 18

Excessive GH secr post puberty
Confined to feet skull scaps rubs and organs
Cause insulin res diabetes mellitus
Often GH prod pit adenoma, slow progression

Question 19

GH causing diabetes mellitus

Answer 19

Gh has diabetogenic activity esp in carnivores cause hyperglyc cause ins res

Question 20

Acromegaly symptoms

Answer 20

Gait abnormal and stiff
Incr appetite weight gain urination and thirst
Excess panting 
Skin thickening and folds
Noisy breathing
Tongue enlargement
Cat has incr interdental space

Question 21

Acromegaly diagnosis

Answer 21

Measure incr plasma GH or IGF1 (as GH is pulsatile)

Question 22

Acromegaly treatment options

Answer 22

Surgery
Somatostatins
Radiotherapy