Pituitary Physiology

Question 1

what does the posterior pituitary gland secrete

Answer 1

oxytocin and ADH

Question 2

oxytocin function

Answer 2

allows the milk to be released when women breast feed

Question 3

where are the posterior pituitary gland secretions formed

Answer 3

• These hormones are synthesized in the body of the nerve cells in the hypothalamus, the gland is an extension of these nerve cells
• Secretions controlled by neurons

Question 4

describe the formation and storage of ADH

Answer 4

• An octapeptide that is synthesised in the hypothalamus in neuron cell bodies. It is transported down neuron axons to nerve terminal in the posterior pituitary gland, where it is stored in granules.
• It is released into the blood when action potentials down the nerves lead to Ca²⁺ dependent exocytosis.

Question 5

what does the anterior pituitary gland secrete

Answer 5

ACTH, TSH, FSH, LH, PRL and STH

Question 6

what are secretions to the anterior pituitary gland controlled by

Answer 6

inhibitory and releasing hormones - secretions first absorbed by capillaries at the base of the hypothalamus and then to pituitary

Question 7

gonadotropins

Answer 7

eg LH and FSH

regulate growth, sexual development and normal reproductive function

stimulate production of testosterone and E2 (oestrogen)

Question 8

E2

Answer 8

estradiol

an oestrogen

Question 9

steroids - pituitary and peripheral hormones

Answer 9

pituitary - ACTH

peripheral - cortisol

Question 10

GH - pituitary and peripheral hormones

Answer 10

pituitary: GH
peripheral: IGF-1

Question 11

suppression test

Answer 11

performed if it is suspected that too much hormone produced

Question 12

stimulation test

Answer 12

performed if it is suspected that too little hormone is produced

Question 13

insulin stress test

Answer 13

suspected glucose, cortisol, GH deficiency

involves giving the patient IV insulin to make the hypoglycaemic, this stress should stimulate the hypothalamus and cause glucose, GH and cortisol levels to rise

eg if werent producing GH that curve wouldnt rise

Question 14

synacthen test

Answer 14

Synthetic ACTH, performed when there is a suspected lack of cortisol

cortisol levels checked at 0, 30 and 60 minute intervals

Question 15

what test is the gold standard for assessing the integrity of the HPA

Answer 15

insulin stress test

Question 16

what is a non functioning pituitary adenoma

Answer 16

one that doesnt secrete any hormones

Question 17

complications of NFPA if extends upwards

Answer 17

compression of optic chiasma - bitemporal hemianopia

Question 18

complicationsof NFPA if it extends laterally

Answer 18

cavernous system

• CNIII - several eye movements and dialted pupil
• CNIV and CNVI - problems with specific eye movements

CNV (I and II)

internal carotid artery

cavernous sinus

Question 19

complications of NFPA if it affects the pitutiary

Answer 19

hypo - adrenalism, thyroidism, gonadism

diabetes insipidus if posterior pituitary affected

GH deficiency

Question 20

difference in size between a micro and macro adenoma

Answer 20

1cm

Question 21

pituitary carcinoma

Answer 21

rare, and often functional

metastasize late after multiple recurrences

Question 22

craniopharyngioma

• what is it derived from

Answer 22

• brain tumour derived from pituitary gland embryonic tissue - Rathke’s pouch
• most common childhood intracranial tumour
• most arise in the sella

Question 23

who do craniopharyngiomas most commonly occur in

Answer 23

children

also adults in 50s and 60s

Question 24

describe the progression of a craniopharyngioma

Answer 24

slow growing, cystic and may calcify

Question 25

clinical features of craniopharyngiomas

• presentation in adult and child

Answer 25

over 50% present in children with growth failure

headaches and visual disturbances (compression of optic chiasma)

adults may present with amenorrhoea

Question 26

investigation of craniopharyngiomas

Answer 26

CT/MRI

Question 27

treatment and prognosis of craniopharyngiomas

Answer 27

surgery ± post-op radiation

prognosis is excellent, especially if it is <5cm