Pituitary

Question 1

Which hypothalamic hormones stimulate what pituitary hormones

Answer 1

GHRH- GH
GnRH- LH and FSH
TRH- TSH and Prolactin
Dopamine- inhibits prolactin
CRH- ACTH

Question 2

Contraindications to the CPFT

Answer 2

• Ischaemic heart disease
• Epilepsy
• Untreated hypothyroidism (impairs the GH and cortisol response)

Question 3

Summary of CPFT

Answer 3

1. Fast patient overnight, ensure good IV access, weigh patient
2. Mix into 5ml syringe: insulin dose (0.15 units/kg), TRH 200mcg, LHRH 100mcg - give IV
3. Bloods: basal thyroxine plus glucose, cortisol, GH, LH, FSH, TSH, prolactin every 30min for
   1 hour- Glucose, cortisol, GH up to 2 hours
4. Replacements: urgent hydrocortisone, T4, oestrogen, GH

Question 4

Interpretation of Insulin aspect of CPFT

Answer 4

Insulin should cause hypo - <2.2mmol/L- therefore increasing ACTH and GH

oAdequate cortisol response=↑greater than 170nmol/l to above 500nmol/l.

o Adequate GH response=↑greater than 6mcg/L

Question 5

Interpretation of TRH aspect of CPFT

Answer 5

Should raise TSH and prolactin (usually dopamine inhibits prolactin but if hypothyroid prolactin is high due to lack of neg feedback)

o The normal result is a TSH rise to>5mU/l (30 min value>60 min value)
o Hyperthyroidism=TSH remains suppressed
o Hypothyroidism=exaggerated response.

Question 6

GnRH interpretation of CFPT

Answer 6

Should increase LH/FSH

Peak around 30/60 mins
LH should > 10 U/l and FSH should > 2 U/l.

An inadequate response=possible early indication of hypopituitarism.

Gonadotrophin deficiency is diagnosed the basal levels rather than the dynamic
response.
§ Males = low testosterone in the absence of raised basal gonadotrophins
§ Females = low oestradiol without elevated basal gonadotrophins and no
response to clomiphene.
§ Pre-pubertal children should have no response of LH or FSH to LHRH.

Question 7

Difference in size of micro and macro adenoma

Answer 7

• Microadenoma < 10mm, usually benign

* Macroadenoma > 10mm, aggressive

Question 8

Differentials of different prolactinaemia

Answer 8

Non-functioning pituitary adenoma– ↑↑ prolactin (1000-5000)

Prolactinoma– ↑↑↑ prolactin (>6000), no in ↑ in GH (>10) and cortisol (>550nM)

Acromegaly- ↑↑GH (even before baseline), ↑ Prolactin, no ↑ in cortisol

Question 9

Treatment of prolactinoma

Answer 9

1st line Mx: Replacements (hydrocortisone, T4, oestrogen, GH), DA agonists (cabergoline, bromocriptine)- due to hypopituitarism

2nd line Mx: Transphenoidal excision (if visual/pressure Sx not responding to medical Tx)

Question 10

Treatment of Non functioning Pit adenoma

Answer 10

Cabergoline/bromocriptine- dopamine agonists; watch and wait if asymptomaticCan do nothing if not causing patients any Sx

Question 11

Treatment of Acromegaly

Answer 11

Mx:
1. Transsphenoidal surgery (best)
2. Pituitary radiotherapy (if surgery fails)
3. Cabergoline
4. Octreotide (expensive) - somatostatin analogue
(cannot stop once started)
5. GH antagonist - pegvisomant

Question 12

Causes of excess ADH

Answer 12

Lung paraneoplastics- usually small cell
SSRI
SIADH

Question 13

Causes of depleted ADH

Answer 13

Diabetes Insipidues
Neurogenis
Nephrogenic- lithium