PPID / EQUINE CUSHING'S PROTOCOLS:
DIURNAL CORTISOL RHYTHM TEST
For the BET Cushing’s Screen (Diurnal Cortisol Rhythm) the following
protocol is suggested:
~ Two samples taken 8-10 hours apart
~ Fasting, no grain for at least 5 hours before drawing the sample
> (grass and hay are fine)
~ Do not unduly stress the animal, i.e. normal exercise, turnout
> routine
SAMPLE TIME>>>>>>>>>>>>>> >>>>>>HORMONES TO ASSAY
AM >>>>>>>>>>>>Total T4 >>>>>>>>Insulin>>>>>>>>> Cortisol
PM SAMPLE >>>> Total T4 >>>>>>>>Insulin>>>>>>>>> Cortisol
(8 to 10 hours later)
Required: Two mL of serum or plasma at each time period. Sample should be
separated and sent in clean, labeled, unbreakable vial.
LOW DOSE DEXAMETHASONE TEST
~ We do NOT recommend using Dexamethasone on laminitic or
> pregnant animals.
~ A normal horse will have a cortisol suppressed below 10 ng/mL.
SAMPLE TIME>>>>>>>>>>>>>> >>>>>>HORMONES TO ASSAY
Sample #1 (taken at 4-6 PM) >>>>>>> >>>>>>>> >>>>> Cortisol
>>>>>>>>>Administer 0.04 mg/kg Dexamethasone IM
>>>>>>>>>>>>>> (20 mg for a 1000 pound horse)
Sample #2 (18-20 hours later noon next day)>>>>>>>>Cortisol
Required: Two mL of serum or plasma at each time period. Sample should be
separated and sent in clean, labeled, unbreakable vial.
DIURNAL CORTISOL RHYTHM AND LOW
DEXAMETHASONE SUPPRESSION TESTS IN THE
SAME ANIMAL
~ Draw the final sample the next day around noon (18-20 hours later).
~ Separate the serum, label all three samples and send them at the
> same time.
SAMPLE TIME>>>>>>>>>>>>>> >>>>>>HORMONES TO ASSAY
AM(between 8-10 am, before breakfast)>Total T4>>> Insulin>>Cortisol
PM( 8-10 hours later before dinner)>>>>Total T4>>> Insulin>>Cortisol
>>>>>>>>>>>>Administer 0.04 mg/kg Dexamethasone IM
>>>>>>>>>>>>>>>>>>>>(20 mg for a 1000 pound horse)
Post DEX>>>>>>>>>>>>>>>>>> > -------->>>>>------- > > Cortisol
(18-20 hours later, around noon next day)
ACTH TEST
~ A normal horse will have an ACTH level of less than 30 pg/mL.
SAMPLE TIME>>>>>>>>>>>>>> >>>>>>HORMONES TO ASSAY
Anytime >>>>>>>>>>>> >>>>>>>>>> >>>>>>>>>>>>>>>>>ACTH
~ One mL of EDTA PLASMA, HARVESTED and FROZEN,
> in PLASTIC VIAL sent OVERNIGHT is required for ACTH test.
VALUES EXPECTED ON NORMAL HORSES
Insulin>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >2 - 25 µI.U./mL Cortisol (resting)>>>>>>>>>>>>>>>>>>>>> >>>> 20 – 90 ng/mL
Cortisol - post DEX >>>>>>>>>>>>>>>>>>> Less than 10 ng/mL
Cortisol rhythm >>>>>>>>>>>>>>>>> >>>>>>Greater than 30%
ACTH >>>>>>>>>>>>>>>>>>>>>>>>>>>>> > Less than 30 pg/mL
