Approach to Small Animal patient with suspected Hyperadrenocorticism Flashcards
Hyperadrenocorticism in small animals is rare (T/F)
False!About the same as diabetes,
More common than renal failure
State 2 causes of hyperadrenocorticism
Spontaneous and Iatrogenic
State 2 causes of spontaneous hyperadrenocorticism
85% Pituitary dependent
15% Adrenal dependent
Most likely due to a tumour
What hormone does the pituitary gland releases (in regards to hyperadrenocorticism)
ACTH
Adrenocorticotrophic hormone
Effect of ACTH
Travels to adrenal gland and stimulates Zona fasciculata to release cortisol
Function of cortisol
Stress Response: Helping to mobilize energy and resources in times of stress or danger.
Glucose Regulation: Cortisol increases blood sugar levels by promoting glucose production in the liver (gluconeogenesis) and reducing glucose uptake by tissues, ensuring an adequate energy supply during stress.
Anti-inflammatory Effects: Cortisol has anti-inflammatory properties and suppresses the immune system, helping to modulate the body’s response to injury, infection, or inflammation.
Metabolism: It influences metabolism by promoting the breakdown of fats and proteins, providing additional energy sources during stress or fasting.
Blood Pressure Regulation: Cortisol plays a role in regulating blood pressure by influencing the responsiveness of blood vessels to other hormones.
Immune System Regulation: It modulates the immune system, balancing its activity to prevent excessive inflammation or immune responses.
Circadian Rhythm Regulation: Cortisol levels follow a circadian rhythm, with higher levels in the early morning to help wake up the body and lower levels at night to support sleep.
Does the body use negative or positve feedback to maintain cortisol levels in body
Negative feedback
Clinical signs of hyperadrenocorticism
Polyuria and polydipsia
Dermatological changes
Abdominal distension
Polyphagia
Lethargy
Respiratory signs
Muscle weakness
Obesity
Haemostatic abnormalities
Reproductive problems
Neurological signs- Myotonia
What biochemistry results do you expect to see of a patient with Hyperadrenocorticism
Increased Alkaline Phosphatase- Increased bone formation
Increased cholesterol- Body’s cells do not respond effectively to insulin.
Increased glucose
Increased ALT, GGT, AST
Increased bile salts
Decreased urea and creatinine
What haematology results do you expect to see of a patient with Hyperadrenocorticism
Stress leucogram
Neutrophilia
Lymphopenia
Rosinopenia
Monocytosis
Erythrocytosis
What urinalysis results do you expect to see of a patient with Hyperadrenocorticism
Low SG
Proteinuria
Urinary tract infection
Glucosuria
Outline ACTH stimulation test
Purpose: The test evaluates the adrenal glands’ response to adrenocorticotropic hormone (ACTH), which stimulates the production of cortisol.
Procedure:
a. A baseline blood sample is taken to measure cortisol levels.
b. Synthetic ACTH, called cosyntropin, is administered either through an injection or intravenously.
c. Additional blood samples are collected at specified intervals to measure cortisol levels in response to ACTH stimulation.
Interpretation:
a. Normal Response: A healthy adrenal gland responds to ACTH by increasing cortisol production, leading to elevated cortisol levels in the blood.
b. Abnormal Response: Reduced cortisol response may indicate adrenal insufficiency, while an excessively high response may suggest Cushing’s syndrome.
Outline Low dose dexamethasone suppression test
Purpose:
To assess the suppressibility of cortisol production by the adrenal glands in response to low-dose dexamethasone, a synthetic glucocorticoid.
Indications:
Suspected Cushing’s syndrome, which is characterized by excessive production of cortisol.
Procedure:
a. Baseline Measurements:
Collect a blood sample in the late evening or at bedtime to measure baseline cortisol levels. This is typically done between 11:00 PM and midnight.
Establish a baseline value to compare with cortisol levels after dexamethasone administration.
b. Administration of Dexamethasone:
Administer a low dose of dexamethasone (usually 1 mg) orally.
Dexamethasone is a synthetic glucocorticoid that normally suppresses the release of adrenocorticotropic hormone (ACTH) from the pituitary gland, leading to decreased cortisol production by the adrenal glands.
c. Post-Dexamethasone Measurements:
Collect blood samples for cortisol measurement the next morning (usually between 8:00 AM and 9:00 AM), approximately 8 hours after dexamethasone administration.
Compare the post-dexamethasone cortisol levels with the baseline levels.
Interpretation:
Normal Response: In healthy individuals, the administration of dexamethasone suppresses cortisol production, resulting in low post-dexamethasone cortisol levels.
Abnormal Response: In individuals with Cushing’s syndrome, there may be a lack of suppression, and cortisol levels remain elevated despite dexamethasone administration.
Identifying the cause of cushings
Specific endocrine tests
Diagnostic imaging
How do you differentiate between a pituitary dependent or a adrenal dependent hyperadrenocorticism
PD - HAC results in increased ACTH concentrations
AD - HAC results in suppression of ACTH secretion
