Pituitary - clinical

Question 1

Describe the thyroid axis

Answer 1

Hypothalamus - releases TRH (thyrotoprin releasing hormone)

Pituitary - releases TSH (thyroid stimulating hormone)

Thyroid - releases T3 + T4

Question 2

What bone surrounds the pituitary

Answer 2

sphenoid

Question 3

What is the ‘pocket’ in which the pituitary is found called?

Answer 3

pituitary fossa

Question 4

What is the sella turcica

Answer 4

Turkish saddle shape of the sphenoid bone

Question 5

What is hemianopia

Answer 5

blindness over half of the visual field.

Question 6

How and why does compression of the optic chiasma by a pituitary tumour affect the vision

Answer 6

The pituitary tumour will compress the optic chiasma, where the optic nerves from the nasal retina cross.

When they are compressed they no longer work, so the nasal retina (which picks up light from the temporal visaul field) no longer produces an image.

Therefore compression of the optic chiasma of a pituitary tumour causes a loss in temporal vision (hemianopia).

Question 7

How can hypopituitarism be caused by a tumour?

Answer 7

The tumour prevents hypothalamus released hormones to reach the pituitary, causing a decrease in pituitary activity.

Question 8

How can you test for pituitary hypofunction

Answer 8

PRL = lactation 
GH = IGF-1 (insulin tolerance test, insulin-like growth factor 1)
TSH = T4,T3
LH = testosterone/estradiol
ACTH = cortisol

Question 9

Why would people with a hypopituitism still have a high PRL

Answer 9

There is no negative feedback to the pituitary from the periphery, only comes from dopamine inhibition from hypothalamus; as tumour stops dopamine moving down pitiutary stalk, the prolactin rises because that dopamine inhibition doesn’t occur.

Question 10

What is the size definition of a micro/macroadenoma

Answer 10

micro = <10mm
macro = >10mm