Adrenal - Ex 4 Flashcards
Canine Hyperadrenocorticism Signs
- middle-aged to older dogs
- PU/PD
- Polyphagia
- Pendulous abdomen
- Panting
- Hepatomegaly
- Muscle weakness
- Lethargy
- Lameness
- Endocrine alopecia
- Pyoderma
- Demodex
- Calcinosis cutis
Canine Hyperadrenocorticism - Lab Abnormalities
CBC
- stress leukogram (neutrophilic, monocytosis, lymphopenia)
- thrombocytosis
Chem
- inc ALP (stress)
- hypercholesterolemia
- hyperglycemia
U/A
- USG < 1.020
- Proteinuria
- **This helps differentiate from hypothyroidism in dogs
What kind of hyperadrenocorticism do MOST dogs have?
85% have pituitary dependent disease
- excess prod of ACTH = high
- bilateral adrenocortical hyperplasia (large adrenal glands)
What kind of hyperadrenocorticism do 15% of dogs have?
15% have adrenal tumors
- ACTH = low
- Unregulated production of cortisol
- Unilateral adrenal enlargement - one large adrenal gland
- typically large breed dogs
- tx: Sx
Iatrogenic hyperadrenocorticism
Chronic Steroid Use
The adrenal glands are fried in these patients - very small
Canine Hyperadrenocorticism Dx
- Rule out Cushing’s
- Urine cortisol:creatinine ratio (Low - rule out cushing’s; High - cushing’s is differential) - Initial Screening
- LDDST
- ACTH Stim Test - Differentiate PDH from ADH
- HDDST
- Endogenous ACTH
Urine Cortisol:Creatinine Ratio
Cortisol excretion in the urine increases as blood cortisol concentration increases
Sensitive, but not specific
With hyperadrenocorticism, the urine cortisol:creatinine ratio will be?
Increased
Low Dose Dexamethasone Suppression Test (LDDST)
- Dexamethasone
- inhibits CRH/ACTH/Cortisol
- Does not interfere w/ cortisol measurement
In a healthy animal, the LDDST should result in
A decrease in cortisol in both 4h and 8hr
In a dog with hyperadrenocorticism, the LDDST should result in
No change in cortisol (at least no change at 4h)
LDDST - HAC dog (PDH)
suppression at 4hr but NOT at 8 hr
LDDST - HAC dog (PDH or ADH)
no suppression at 4 or 8 hr
ACTH stim test
ACTH stimulates production of cortisol
In a healthy animal, the ACTH stim test should result in
mild increase in cortisol
In a dog with HAC (PDH or ADH), the ACTH stim test should result in
A MARKED increase in cortisol
In a dog with HAC (iatrogenic), the ACTH stim should result in
NO Stimulation! The adrenal glands are gone (atrophy)
ACTH stim Interpretation
Mild inc
Exaggerated inc
No inc
mild inc: normal
exaggerated inc: Cushing’s
No inc: iatrogenic Cushing’s
If both LDDST and ACTH tests are negative…
you have ruled out Cushing’s
Additional Testing - Endogenous ACTH and HDDST
Endogenous ACTH concentration
- ACTH is unstable and req’s special handling
- normal to increased ACTH = PDH
- low to undetectable ACTH = ADH
HDDST
- Suppression at 4 or 8h = PDH
- No suppression = PDH or ADH
A dog with Cushing’s dz has a low endogenous ACTH concentration, this is most consistent with
ADH - HAC
A dog with Cushing’s dz has a high endogenous ACTH concentration, this is most consistent with
PDH - HAC
A dog with Cushing’s dz suppresses w/ HDDST, most consistent with
PDH - HAC
A dog with Cushing’s dz does not suppress with HDDST, most consistent with
HAC, but can’t tell what kind
What is the most common equine endocrinopathy?
Equine Cushing’s Dz: Pituitary Pars Intermedia Dysfunction (PPID)
Equine Cushing’s Dz - Lab Abnormalities
CBC
- stress leukogram
- anemia
Chem
- Hyperglycemia
- Hyperlipidemia
- Inc liver enzymes
- Glucosuria
Equine Cushing’s Dz - Pathogenesis
Pituitary adenoma
Excessive secretion of proopiomelanocortin-derived peptides
- ACTH, MSH, CLIP & beta-endorphin
- results in excess cortisol production
What is the most accurate test to Dx Equine Cushing’s?
Dexmethasone Suppression Test
- most accurate, but no longer recommended!
Dex is assoc’d with laminitis
Lack of plasma cortisol suppression 19-24 hr post dex = Cushing’s
Equine Cushing’s Dx - Endogenous ACTH
Elevations are suggestive of PPID
Equine Cushing’s Dx - TRH Stimulation
Theory: cortisol increases 1 hour post TRH with PPID
- cortisol does not inc in most healthy animals
Advantage: no dex administration
What tests are NOT recommended to Dx Equine Cushing’s
Baseline cortisol
- many horses have normal to dec cortisol levels
Basal insulin levels
- large variation in both PPID and healthy
Urine cortisol:creatinine
- not validated
ACTH stim test
- not very useful in horses with PPID
- many PPID horses have low cortisol levels
