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chemical pathology > pituitary > Flashcards

pituitary Flashcards

1
Q

Pituitary failure causes hypotension. True or false?

A

false

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2
Q

why do you get hypotension in adrenal insufficiency

A

When you are hypoadrenal, TWO hormones are missing:
o Aldosterone
o Cortisol

  • BP is low in Addison’s disease
  • Aldosterone deficiency is what causes hypotension
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3
Q

What complication of a large pituitary tumour should you look out for

A
  • Bitemporal hemianopia
  • tumor presses on the optic chiasm

Humphrey’s testing helps to show any blind spots in the visual fields/ areas where lack vision

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4
Q

which hormones are released by the anterior pituitary

A

GHRH acts on GH
Dopamine acts on prolactin
TRH acts on prolactin and TSH
LHRH/GnRH acts on LH
CRH acts on ACTH

REMEMBER: High prolactin can be due to hypothyroidism

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5
Q
  • 30 year old presenting with galactorrhoea
  • A CT scan of her pituitary shows a large (2cm) macroadenoma
  • Prolactin levels are 30,000 (normal < 600)
  • She has not had sexual intercourse

QUESTION 3: What is the diagnosis of this 30-year-old?

A
  • Prolactinoma

IMPORTANT: If Prolactin > 6,000, it is ALWAYS a prolactinoma- there is no other possible diagnosis

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6
Q

Describe the important hormones in the hypothalamopituitary axis

A
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7
Q

When would you do a combined pitutary function test?

What are the contraindications?

A

Assessment of all components of anterior pituitary function used particularly in pituitary tumours (to see if tumour is compressing on other structures and therefore compromising their function)
or following tumour treatment.

C/I?

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

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8
Q

What effect does hypothyoridism have on prolactin?

A

Hypothyoridism–>high TSH/TRH–> high prolactin

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9
Q

Micro vs macroadenoma

A

Micro: <1cm

Macro: >1cm

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10
Q

If someone had a prolactinoma, what other test should you do?

A

CPFT

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11
Q

What is administered during a CPFT?

A

1. Insulin:

Induces hypoglyucaemia <2.2 mmol/L (*ensure no C/I and monitor blood glucose regularly; resuce with 50ml of 20% dextrose if needed)

–>would stimulate CRH and GHRH

–>End hormones- adequate increase in CORTISOL and GH

  1. TRH: would stimulate TSH and prolactin –> T3/T4

3. GnRH: stimulates LH and FSH

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12
Q

What are the contraindications to a CPFT?

A

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

**basc you need to be able to handle the hypoglycaemia induced by the insulin**

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13
Q

Procedure for CPFT

A
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14
Q

WHat are the end hormones measured after CPFT?

A
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15
Q

How frequently do you measure hormones in CPFT?

A
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16
Q

How to interpret results of CPFT?

Prolactinoma vs non-functining pituitary adenoma

A

1) prolactinoma: prolactin would be high (>6000)and everything else would be suppressed - i.e. you don’t see an adequate rise after the stimulation test.
2) non-functioning pituitary adenoma: prolactin would be slightly high (but <6000) and everything else would be similarly suppressed i.e. inadequate rise following stimulation test

17
Q

What is the difference between prolactinoma and non-functinoing pitiitary adenoma?

How does prolactin get raised in non-functioning pituitary adenoma?

A

Prolactinoma: prolactin >6000

Non-functioning adenoma: raised but <6000

*raised because obstruction of stalk–>dopamine is inhibited–>prolactin rises*

18
Q

Management of pituitary failure due to a) prolactinoma and b) non-functioning pituitary adenoma

A
  1. Prolactinoma
    - IV hdyrocortisone first
    - then thyroxine, GH and oestrogen replacement
    - no need to replace fludocortisone
  2. non-functioning adenoma
    - IV hydrocortisone OR prednisolone (preferred as longer half life, more physiological)
    - then thyroxine, GH and oestrogen replacement
    - no need to replace fludocortisone

*so main diff: IV hydrocortisone in prolactinoma vs

19
Q

Management of prolactinoma vs non-functinig pituitary adenoma

A

Prolactinoma: dopamine agonist (bromocriptine/cabergoline)

Non-functioning adenoma: don’t respond to dopamine agonists (not sure why) - SO SURGERY is mainstay!!

20
Q

How would a TSHoma present?

A
  • Patients present with typical features of hyperthyroidism such as palpitation, tremor, weight loss, and diaphoresis.
  • The pituitary tumour is usually a macro-adenoma.
  • High free T4 and free T3 levels
  • normal or elevated TSH (the alpha subunit is usually elevated)
  • Slightly high prolactin levels
    • only slightly elevated, as opposed to prolactinomas in which the prolactin level is usually very high
    • stalk effect
  • The immunostaining of the tumour will show diffuse staining for TSH.
21
Q

What test is used to diagnose acromegaly?

A
  1. Initial test: raised IGF-1 levels
  2. Diagnostic test: Glucose tolerance test

*despite glucose administration, GH is not suppressed –> acromegaly*

22
Q

What test is used to diagnose Cushing’s syndrome?

A

Low dose dexamethasone suppression test

23
Q

What is used to diagnose addison’s disease?

A

short Synacthen test

24
Q
A
25
Q

Treatment for acromegaly

A

GH antagonist can be used if ALL THESE FAIL (pegvisomant)

26
Q

What effect does acromegaly have on the bones?

A

osteoporosis

27
Q

Ivx for GH deficiency

A
28
Q

What does this picture show?

A

Adrenal glands

29
Q

What hormones are produced by the posterior pituitary?

A
  1. ADH
  2. oxytocin
30
Q

Causes of high ADH

A
  • Lung - lung paraneoplasias – usually small cell lung cancer, pneumonia
  • Brain - Traumatic brain injury, meningitis, primary or secondary tumours
  • Iatrogenic – SSRIs, Amitryptiline, carbamazepine, PPIs
  • SIADH – Euvolaemic Hyponatraemia
31
Q

Causes of ADH failure

A

Diabetes insipidus –increased diuresis due to either failure of production or insensitivity to ADH, leads to decreased urine osmolality and increased serum osmolality

Neurogenic – Failure of production – 50% idiopathic

Nephrogenic – commonly iatrogenic – lithium, also hypercalcaemia, renal failure Dipsogenic – Failure/damage to hypothalamus and thirst drive, hypernatraemia without increased thirst response.

chemical pathology (22 decks)

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