Pituitary Function And Disease

Question 0

Regulation of TSH

Answer 0

Hypothalamus
TRH
Anterior pituitary
TSH
Thyroid gland
T3/T4->negatived feedback on hypothalamus and ant. pit. 
Inhibited by somatostatin

Question 1

Tumours

Answer 1

Mostly slow growing 
Over production of one hormone,under production of the others 
Pressure on surrounding structures
Prolactinoma-> 40-45% 
GH secreting-> 20% 
ACTH secreting-> 10-15% 
LH/FSH/TSH rare 
Non secreting20-25%

Question 2

Posterior pituitary hormone regulation, AVP

Answer 2

Stimulated by increase in body fluid osmolality, fall in BP and stress
Actions:
Vasoconstriction via V1 receptors
Increased permeability in distal convoluted tubule->increase water reabsorption via V2 receptors
Stimulates ACTH release

Question 3

Posterior pituitary regulation, oxytocin

Answer 3

Stimulated by suckling and cervical stimulation
Release is via positive feedback control
Actions:
Stimulate milk let down 
Uterine smooth muscle contraction 
Maternal/sexual behaviour

Question 4

ACTH

Answer 4

Hypothalamus
Corticotrophin releasing hormone
Anterior pituitary->pro-opiomelenocortin
ACTH
Adrenal cortex
Synthesis and release of cortisol

Question 5

Gonadotropins

Answer 5

Hypothalamus 
Gonadotropin releasing hormone
Anterior pituitary 
LH and FSH 
Ovaries/testes 
Sex hormones

Question 6

Growth hormone

Answer 6

Hypothlamus
Growth hormone releasing hormone
Anterior pituitary 
Growth hormone
Liver
IGF-1
Growth, development metabolism
Inhibited by high prolactin and somatostatin

Question 7

Prolactin

Answer 7

Hypothalamus
TRH
Anterior pituitary 
Prolactin
Mammary glans
Milk release, breast growth and develope ment 
Inhibited by dopamine

Question 8

TRH stimulation test

Answer 8

Give patient TRH
Normal reaction-> increased TSH->increased T3/T4
Secondary hyperthyroidism->deficient TSH,release not stimulated-> low T3/T4

Question 9

Oral glucose tolerance test

Answer 9

Suppression test
Give patient glucose to cause high glucose plasma
Normal reaction-> suppression of GH release-> decreased GnRH, increased SST
Ant. Pit tumour-> failure to lower GH secretion

Question 10

Management of tumours

Answer 10

Pharmacological
Surgery
Radiotherapy
Potential side effects of hypopituitarism and damage to optic pathway

Question 11

Hyperprolactinaemia

Answer 11

Most common cause of Prolactinoma 
Symptoms: 
Loss of fertility/libido 
Galactorrhoea
May also be due to damage to the pituitary stalk-> loss of inhibitory influence of hypothlamus 
Treatment:
Dopamine receptor agonist-> inhibit prolactin secretion and shrink tumour-> bromocriptine, carbergoline 
Surgery or radiotherapy

Question 12

Acromegaly

Answer 12

Excessive GH secretion in adulthood (gigantism in childhood) 
GH secreting tumour is most common cause
Symptoms:
Glucose intolerance
Large feet, hands and face-> change
Headaches, visual distrubances
Loss of periods/impotence 
Sleep apnoea, tiredness 
Treatment:
Surgery 
Radiotherapy 
Somatostatin analogues 
Dopamine agonists in tumours that acquire receptors

Question 13

Cushings syndrome

Answer 13

Excessive glucocorticoids
Endogenous or exogenous
Main causes is ACTH secreting tumour 
Increased cortisol-> increased glucocorticoids 
Tumours don't respond to negative feedback 
Treatment:
Surgery 
Radiotherapy

Question 14

Hypopituitarism

Answer 14

Deficiency of one or more of the pituitary hormones
Pan-hypopituitarism=deficiency of all pituitary
Usually pituitary adenoma or surgery
Damage to pituitary stalk
Decreased…
GH->stunted growth
TSH->secondary hypothyroidism
ACTH->adrenal insufficiency
ADH->diabetes insipidus
Gonadotropin->young, delayed puberty. Old, infertility
Treat with hormone replacement