Adrenocortical Function Flashcards
What does the hypothalamus release for the regulation of cortisol and aldosterone secretion?
Corticotropin-releasing hormone
What does CRH cause the pituitary to release?
Adrenocorticotropic hormone and others
What does ACTH cause the adrenal glands to do?
Secrete cortisol, aldosterone, and other steroids
What does low cortisol promote?
Secretion of CRH and ACTH
What inhibits the secretion of CRH and ACTH?
High cortisol
What is aldosterone secretion promoted by?
ACTH, angiotensin II, hyperkalemia, and hyponatremia
What is the secretion of aldosterone inhibited by?
Atrial natriuretic peptide
What does aldoseterone promote?
Renal retention of Na and Cl
Renal excretion of K and H
When is the peak secretion of cortisol in dogs and horses?
Morning
When is the peak secretion of cortisol in cats?
Evening
What is most of the cortisol bound to?
Protein: 40% transcortin, 50% albumin
What percent of cortisol is free?
5-10%
What is the half-life of cortisol in dogs?
1.5 hours
What happens when cortisol and aldosterone bind to receptors in cells?
Gluconeogenesis Protein catabolism Lipolysis Immune response H2O balance
What is cortisol and aldosterone removed by?
Hepatocytes
Some is excreted in the urine
What is the sample needed for cortisol?
EDTA-plasma
What is the sample needed for aldosterone?
Serum or heparinized plasma
What is the sample needed for ACTH?
EDTA-plasma
What are causes of hypercortisolemia?
Pituitary-dependent hyperadrenocorticism (Cushing's) Functional adrenocortical neoplasia Stress induced hypercortisolemia Ectopic production of ACTH Exogenous ACTH administration
What are common lab findings of leukogram with hypercortisolemia?
Steroid leukogram
What are common lab findings of chemistry profile with hypercortisolemia?
ALP in dogs
Hyperglycemia
Hypercholesterolemia
Lipemia
What are common lab findings of urinalysis with hypercortisolemia?
Relatively unconcentrated, isosthenuric or hyposthenuric urine
Glucosuria in horses
What are causes of hypocortisolemia?
Primary hypadrenocorticism (Addison’s)
Secondary hypoadrenocorticism (ACTH deficiency)
Atypical primary hypoadrenocorticism
Iatrogenic hyperadrenocorticism
Iatrogenic hypoadrenocorticism
Treatment with ketoconazole or trilostane
What are common lab findings of leukogram with hypocortisolemia?
Absence of stress leukogram in ill, stressed patients
What are common lab findings of chemistry profile with hypocortisolemia?
Hyponatremia, hypochloremia, hyperkalemia, hypercalcemia, hypoglycemia, azotemia
What are common lab findings of urinalysis with hypocortisolemia?
Inappropriately low USG with azotemia
What does the urine cortisol to creatinine ratio provide?
A relative rate of of urinary excretion of cortisol
What are causes of normal to increased ACTH?
PDH
Primary hypoadrenocorticism
Perhaps ectopic production of ACTH
What are causes of decreased ACTH?
FAN
Secondary hypoadrenocorticism
Dexamethasone injection
Therapeutic use of steroids
What does the low-dose dexamethasone suppression test screen for?
PDH and FAN
What is high-dose dexamethasone suppression test used for?
Differentiating PDH and FAN after hyperadrenocorticism is diagnosed
When is aldosterone expected to be decreased?
In clinical hypoadrenocorticism
Primary and secondary hyperaldosteronism
What does primary hypoadrenocorticism in dogs do to the aldosteorne:renin ratio?
Decreases it
