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Pituitary adenoma :confusing but important on exam - misshyd
#1
These are the guidelines to approach pituitary incidentalomas
( reference dr.red endocrinology lecture)

1) In deciding how to approach INCIDENTALLY discovered pituitary tumors, first rule out Function ( i.e; hormone production).

2) To R/O functioning adenomas first - do prolactin level, Dexamethasone suppression test, ACTH level, TSH and IGF 1 level depending on the clinical features.

3) Functioning adenomas : Except Prolactinomas, all other functioning adenomas are treated primarily by surgery ( i.e; for secondary hyperthyroidism, acromegaly etc).

4) NON-FUNCTIONING ADENOMAS: If Non functioning adenomas, Surgery is indicated only if mass effects such as Visual field defects , Headaches and Hypopituitarism are present.
If non functioing adenomas are small and asymptomatic --> Follow patients with non functioning microadenomas and small, noninvasive macroadenomas with a 6-month MRI scan and yearly thereafter. If there is no evidence of enlargement after 3 to 5 years, then continue to follow patients clinically .

5) If prolactinomas,
a) Microademomas --> prolactin levels usually > 100
b) Macroadenomas --> Prolactin levels usually very high 500 to 1000. Be aware of HOOK Effect.
c) If high prolactin level encountered on blood tests and cannot be explained by meds/ stress. MRI is the next test. Be aware MRIs do not r/o small microadenomas ( use Bromocriptine ( dopamine agonist) as first line therapy. Surgery done only for those patients not responding to or intolerant of dopamine agonists.
e) If Prolactin Producing Macroadenomas are associated with mass effect --> Still bromocriptine must be tried first. Only if no response, Surgery ( trans sphenoidal resection) is done.
Understand that prolactinomas even when large and causing symptoms , they can shrink with dopamine agonists. Remember that Surgery done for pituitary adenomas is associated with long lasting serious consequences so, whenever possible, medical therapy must be used first line if response can be observed. That is why even in large symptomatic prolactinomas, dopamine agonists are the first step.

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#2
Thank you misshyd...agree for medical treatment first.

I know stalk effect....tumor pressing the pit stalk and interrupt the delivery of dopamine.

What is hook effect? Please say more on it, thanks.
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#3
leave it little bit for residency forever..
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#4
Oh yea, I think I should. Now I feel low and low...
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#5
Thnx misshyd........
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#6
misshyd...thank you.
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#7
For other high yield topic... please leave your high light point...really helpful!
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#8
HOOK EFFECT:

Very high prolactin concentrations can interfere with immunoassay systems resulting in falsely low prolactin determination.this is due to "hook effect" which describes the inhibition of immune complex formation by excess antigen concentrations. this is an important consideration in patients with large pituitary adenomas when the clinical suspicion of prolactinoma is strong, as in patients with amenorrhoea-galactorrhoea or longstanding hypogonadism. appropriate dilution of the serum in such cases helps in accurate estimation of serum prolactin concentration.


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#9
Ohh, next confirmation test is dilution study....I got it, thanks shigella.
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