00:02
Screening tests for hypercortisolism: dexamethasone
suppression, low dose is 1 mg administered
at night.
00:09
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.
00:19
Patient with Cushing's syndrome will not
suppress cortisol normally, syndrome maybe
from the adrenal cortex.
00:28
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.
00:40
24 hour urine free cortisol measurement, 4
times upper limit of normal is diagnostic.
00:48
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.
00:56
Now, I am going to get into more specificities
about how to screen for hypercortisolism,
this will be in current day practice, pay
attention.
01:07
Salivary control, it is a sensitive screening
test, loss of normal or diurnal variation
usually precedes overt hypercortisolism.
01:18
Once again, loss of normal or diurnal, what
does diurnal mean?
Low at the end of the day, high in the morning
of cortisol.
01:29
Relatively easy to do, but requires reliable
labs, measures free hormone only.
01:35
Mildly abnormal screening results may represent
pseudo-Cushing's.
01:38
Pseudo-Cushing's an important topic maybe
due to depression or alcoholism.
01:45
How would you feel if you are depressed?
Hmm, pretty lethargic, alcoholism, pretty
lethargic; psychologically you might be a
little varied.
01:56
Cushing's syndrome: summary of a lab test.
02:00
Adrenal cortisol producing, we have excess
cortisol ACTH is undetectable.
02:08
What kind of hypercortisolism is this, please?
Primary.
02:13
In Cushing's disease, most common endogenous
case.
02:17
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.
02:34
Ectopic ACTH producing tumor, I am going through
this quickly since we have done it already.
02:39
Excess cortisol due to ACTH producing paraneoplastically
by small cell lung cancer; excess not suppressed.
02:50
Excess cortisol, not suppressed, when do-when
done or doing a high dose dexamethasone suppression
test.
02:58
I have abbrevi-abbreviated as Dex.
03:03
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.
03:24
Let's take a look.
03:25
This is called CRH stimulation test.
03:28
CRH, go back to normal, corticotropin releasing
hormone coming out of the hypothalamus works
upon the anterior pituitary to release ACTH.
03:37
Watch this.
03:39
With vasopressin to ACTH dependent Cushing's
syndrome, Cushing's disease, secondary hypercortisolism
will respond, but ectopic ACTH production
will not.
03:50
Let me recap that.
03:52
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,
ectopic.
04:09
High dose dexamethasone suppression test is
going to inhibit the cortisol from whom?
From your anterior pituitary.
04:16
That's high dose dexamethasone.
04:19
If your CRH, corticotropin releasing hormone,
what it will do is that with Cushing's disease,
you will have a response with CRH stimulation
test.
04:32
With ectopic, your hypothalamus has no control
over what is going on in the lung.
04:39
So, ectopic ACTH production will not be influenced
by CRH.
04:46
It helps you distinguish between the two ACTH
dependent.
04:50
Next, discriminate between pseudo-Cushing's
and Cushing's syndrome.
04:55
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.
05:13
So, therefore, important that you are able
to distinguish between Cushing's versus