ChemPath: Pituitary

Question 1

Why doesn’t hypopituitarism cause low blood pressure?

Answer 1

The adrenals are still able to produce aldosterone

Question 2

List the hormones produced by the anterior pituitary

Answer 2

GH

prolactin

TSH

LH

FSH

ACTH

Question 3

List the hormones produced by the posterior pituitary gland

Answer 3

oxytocin and vasopressin

Question 4

Which hypothalamic hormones affect prolactin release?

Answer 4

Dopamine → negative

TRH → positive

NOTE: hypothyroidism causes hyperprolactinaemia

Question 5

How might pituitary failure present in women?

Answer 5

Amenorrhoea and galactorrhoea

Question 6

What size is a macroadenoma?

Answer 6

>1cm

Question 7

What physical manifestation might a macroadenoma of the pituitary gland (>1cm) cause?

Answer 7

Bitemporal hemianopia

NOTE: this can be tested using a visual field test

Question 8

Why would prolactin be very very high? >6,000

Answer 8

always prolactinoma IF NOT PREG

lactation- pregnant woman

Question 9

What is the main problem with prolactinomas?

Answer 9

It might reduce/stop the production of other pituitary hormones (e.g. FSH and LH) or affect the axis

High prolactin in itself is not much of an issue.

Question 10

What is the CPFT?

Answer 10

Combined Rapid Anterior Pituitary Evaluation Panel

Test for pituitary function

Question 11

Which three stimuli of pituitary hormone secretion are used in the CPFT?

Answer 11

• Hypoglycaemia - increases CRH/ACTH and increases GHRH/GH
• TRH - increases TSH and prolactin
• LHRH - increases LH and FSH

Question 12

What safety precautions must you take before subjecting a patient to hypoglycaemia?

Answer 12

• No cardiac risk factors (needs a normal ECG)
• No history of epilepsy
• Ensure good IV access

Question 13

Describe the manifestations of increasing hypoglycaemia?

Answer 13

• Initially, the activation of the sympathetic nervous system will result in sweating, tachycardiac etc.
• When the blood glucose reaches <1.5mM, neuroglycopaenia may occur (loss of consciousness and confusion)

Question 14

What blood glucose concentration is normally required to stimulate the pituitary gland?

Answer 14

<2.2mM give more insulin if doesn’t drop

Question 15

How should a patient be rescued if they experience severe hypoglycaemia during this CPFT?

Answer 15

50ml 20% dextrose

Question 16

How much insulin should a patient with severe hypoglycaemia during a CPFT test receive?

Answer 16

0.15 U/kg

Question 17

Outline the dosing of various drugs in the CPFT.

Answer 17

fast overnight and weigh

• 5mL syringe
• Insulin (0.15 units/kg)
• TRH 200 µg
• LHRH 100 µg

NOTE: the patient may experience a warm flush and vomit when the drug is administered

Question 18

What should be measured in the blood?

Answer 18

• Glucose
• Cortisol
• GH
• LH and FSH
• TSH
• Prolactin

Question 19

How frequently should hormone levels in the blood be measured?

Answer 19

• Every 30 mins for 60 mins - LH, FSH, TSH, prolactin
• Every 30 mins for 120 mins - glucose, GH, cortisol

Question 20

Describe the response you would expect from a normal pituitary gland undergoing the CPFT?

Answer 20

Blood sugar will go down but then it will rise again without any external help. This is due to production of GH and ACTH (and hence cortisol) in response to the metabolic stress.

Question 21

What should be done if a response isn’t observed at a plasma glucose of 2.2 mM?

Answer 21

Give more insulin

Question 22

What level of cortisol and GH is considered a normal response?

Answer 22

Cortisol >550nM

GH >10 IU/L

Question 23

List the order of hormone replacement in someone with panhypopituitarism.

Answer 23

• Hydrocortisone- URGENT
• Thyroxine
• Oestrogen
• GH

NOTE: Fludrocortisone is not necessary because the adrenals can still produce aldosterone

once daily pred now given instead of TDS HCT

Question 24

How should a patient with a prolactinoma be treated?

Answer 24

Dopamine agonists (e.g. cabergoline or bromocriptine)

This reduces the size of the tumour and can avoid surgery

Question 25

What is disconnection hyperprolactinaemia?

Answer 25

Compression of the pituitary stalk by a tumour cuts off the negative effect of dopamine on pituitary prolactin secretion

This results in hyperprolactinaemia

also known as non-functioning pituitary adenoma

Question 26

Why do non-functioning adenomas need surgery?

Answer 26

They do NOT respond to dopamine agonists

Question 27

Why might prednisolone replace hydrocortisone as the first-line steroid replacement agent?

Answer 27

It has a longer half-life meaning that once daily dosing is possible

Question 28

How should you investigate a child with poor growth who is suspected of having a GH deficiency?

Answer 28

• Take a random plasma GH measurement (GH is pulsatile but if you happen to measure it during a pulse and they have detectable GH then it shows that they are produing GH)
• Excercise test
• Insulin tolerance test (effective but dangerous so should NOT be done straight away)

Question 29

Name two tests that may be used to investigate suspected acromegaly.

Answer 29

• Oral glucose tolerance test
• IGF-1 levels

NOTE: the normal ranges for IGF-1 are not fuly resolved and they vary with age

Question 30

acromegaly treatment

Answer 30

surgery- depends on whether tumour around carotids

pit radiotherapy

cabergoline: acromegaly cells may express dopamine receptors and respond to it

octreotide