Screening tests for hypercortisolism: dexamethasone
suppression, low dose is 1 mg administered
Normal individual will have suppressed, normal,
okay, I am walking through this quickly because
I already talked about it, everything that
we talked about discussed is now in verbiage
just to' for reinforcement purposes.
Patient with Cushing's syndrome will not
suppress cortisol normally, syndrome maybe
from the adrenal cortex.
The test is considered positive if the suppressed cortisol
level is greater than 1.8 µg/dl
Using the value 1.8 increases the tests sensitivity
which is the desired characteristic for a screening test.
24 hour urine free cortisol measurement, 4
times upper limit of normal is diagnostic.
Screening tests for hypercortisolism, I went
through just quickly, much of this we already
discussed, make sure that it's firmly implanted
in your head.
Now, I am going to get into more specificities
about how to screen for hypercortisolism,
this will be in current day practice, pay
Salivary control, it is a sensitive screening
test, loss of normal or diurnal variation
usually precedes overt hypercortisolism.
Once again, loss of normal or diurnal, what
does diurnal mean?
Low at the end of the day, high in the morning
Relatively easy to do, but requires reliable
labs, measures free hormone only.
Mildly abnormal screening results may represent
Pseudo-Cushing's an important topic maybe
due to depression or alcoholism.
How would you feel if you are depressed?
Hmm, pretty lethargic, alcoholism, pretty
lethargic; psychologically you might be a
Cushing's syndrome: summary of a lab test.
Adrenal cortisol producing, we have excess
cortisol ACTH is undetectable.
What kind of hypercortisolism is this, please?
In Cushing's disease, most common endogenous
Here, we have excess cortisol due to excess
ACTH, excess cortisol and ACTH is normal or
high, excess cortisol suppression by high
dose dexamethasone suppression test.
Ectopic ACTH producing tumor, I am going through
this quickly since we have done it already.
Excess cortisol due to ACTH producing paraneoplastically
by small cell lung cancer; excess not suppressed.
Excess cortisol, not suppressed, when do-when
done or doing a high dose dexamethasone suppression
I have abbrevi-abbreviated as Dex.
Current day practice: this is a pathophysiology
question that is being increasingly asked
because people are so incredibly familiar
with dexamethasone suppression test that you
want to make sure that you have a full understanding
of the hypothalamo, pituitary, adrenal access.
Let's take a look.
This is called CRH stimulation test.
CRH, go back to normal, corticotropin releasing
hormone coming out of the hypothalamus works
upon the anterior pituitary to release ACTH.
With vasopressin to ACTH dependent Cushing's
syndrome, Cushing's disease, secondary hypercortisolism
will respond, but ectopic ACTH production
Let me recap that.
CRH stimulation test, why would you think
about using this on your exam or with a patient?
You have ACTH dependent tumors, two of them,
what are they again?
Anterior pituitary, ectopic' anterior pituitary,
High dose dexamethasone suppression test is
going to inhibit the cortisol from whom?
From your anterior pituitary.
That's high dose dexamethasone.
If your CRH, corticotropin releasing hormone,
what it will do is that with Cushing's disease,
you will have a response with CRH stimulation
With ectopic, your hypothalamus has no control
over what is going on in the lung.
So, ectopic ACTH production will not be influenced
It helps you distinguish between the two ACTH
Next, discriminate between pseudo-Cushing's
and Cushing's syndrome.
Pseudo-Cushing's refers to the following
conditions: physical stress, visceral obesity,
Poly Cystic Ovarian Syndrome, Anorexia Nervosa,
psychologic stresses, symptoms that may seem
a-a little similar perhaps to Cushing's,
but it's pseudo.
So, therefore, important that you are able
to distinguish between Cushing's versus