physiology of hypoadrenocoticism Flashcards
explain how low blood pressure is detected in the kidneys
- renin release stimulated by baroreceptors in the wal of the afferent arteriole
- cells of the macula densa in the early distal tubule which are stimulated by reduction in NaCl delivery
give an overview of the RAAS system
there are 3 classifications of hypoadrenocorticism. what are they? which ones are important?
- primary hypoadrenocorticism (addisons disease) = loss of adrenal cortex
- secondary hypoadrenocorticism (deficiency of ACTH) = rare
- iatrogenic hypoadrenocorticism (from exogenous steroids)
primary = CR
iatrogenic occurs but usually due to overzealous tx of cushings or acute stop of steroid use
what is addisons disease and what are the causes in dogs
- deficiency of glucocorticoids (cortisol) and mineralcorticoids (aldosterone)
- occurs with loss of 85-90% of adrenal cortex
- caused by idiopathic atrophy (probably immune mediated destruction) or iatrogenic (by drugs or surgery)
briefly describe secondary hypoadrenocorticism
- rare deficiency of ACTH
- cortisol deficiency as result
what is the signalment of hypoadrenocorticism. name breeds which are predisposed
- young-middle aged dogs (median age = 4-6 years)
- 70% females
- any breed but certain predispositions
- extremely rare in cats
breeds:
- standard poodles
- bearded collies
- portuguese water dog
- leonberger
- great dane
- rottweiler
- WHWT and soft coated wheaten terriers
what is the history and clinical signs of addisons
- usually nothing (pathognomonic)
- waxing and waning with non specific signs (chronic) worsened by stress
- if acute usually come in collapsed with marked hypovolaemia and azotaemia
- anorexia,
- vomiting,
- diarrhea,
- PU/PD
- weakness
- lethargy
- depression
explain the pathophysiology of addisons if the deficiency is caused by aldosterone. glucocoticoid?
aldosterone
- loss of Na+, Cl- and H20
- retention of K and H
- pre renal failure (due to low circulation, not issue of kidney themselves)
glucocorticoid
- decreased stress tolerance
- GI signs
- weakness
- appetitie loss
- anaemia
- impaired gluconeogenesis
name common clinical pathology seen in blood analysis in addisons
- lack of stress leukogram on CBC
- anemia (due to erythtocytosis due to lack of cortisol or GI blood loss)
- hyperkalaemia (high K)
- hyponatraemia (low Na)
- hypochloridaemia (low Cl)
- low Na:K ratio
- renal tubular resorption of Na and Cl
- excretion of K and H
- increased renal parameters (due to azotaemia)
- hypoglycemia
- low USG (inappropriately for dehydrated animal)
how do you diagnose addisons
ACTCH stim test
cortisol levels wont change in diseased animal
- sensitive and specific if no prior steroid use (except dex as it doesnt interfere with assay)
how do you treat addisons
- mineralcorticoids (desoxycortone pivalate) to replace aldosterone
- glucocorticoids during crisis or times of stress, not usually needed long term
