Adrenal disease (Yr 4) Flashcards
what is hyperadrenocorticism known as?
cushings disease
what does the medulla of the adrenal gland make?
epinephrine/norepinephrine (adrenaline)
what is produced in the cortex of the adrenal gland?
androgens
glucocorticoids
mineralocorticoids
what does the adrenal gland make its hormones from?
cholesterol
what is the precursor of aldosterone and cortisol?
pregnenalone
what triggers pregnenalone release?
ACTH
what releases ACTH?
anterior pituitary
what triggers cortisol production?
ACTH
what are the general effects of cortisol?
facilitates vasoconstriction
trigger gluconeogenesis
facilitate glucose uptake by muscles
catabolism of muscles (amino acid release)
fatty acid release
what effects does cortisol have on glucose?
gluconeogenesis
insulin resistance
what effects does cortisol have on bone and collagen?
reduce bone formation
reduce calcium absorption in intestines
down regulates collagen synthesis
what effects does cortisol have on amino acids and proteins?
inhibit collagen formation
increases amino acids in serum
decrease amino acid uptake by muscles
inhibit protein synthesis
reduction of immunoglobulins
what effects does cortisol have on wound healing?
delays wound healing
what effects does cortisol have on electrolyte and water balances?
increased diuresis and GFR
increase renal sodium retention
increase potassium excretion
increase intestinal sodium/water absorption
what type of hormone is cortisol?
glucocorticoid
what animals typically present with hyperadrenocorticism?
medium-older age dogs
(rare in cats)
what are the two types of hyperadrenocorticism?
pituitary dependant hyperadrenocorticism
adrenal dependant hyperadrenocorticism
what are the most common signs of hyperadrenocorticism?
PUPD, polyphagia
panting
abdominal distention
endocrine alopecia
hepatomegaly
muscle weakness
systemic hypertension
what are some moderately common signs which might lead you to suspect hyperadrenocorticism?
lethargy
hyperpigmentation
comedones
thin skin
poor hair regrowth
urine leakage
insulin resistant diabetes mellitus
what findings on haematology would be indicative of hyperadrenocorticism?
neutrophilic leukocytosis
lymphopenia
eosinopenia
thrombocytosis
mild erythrocytosis
what findings on biochemistry would be indicative of cushings?
increased ALKP
increased ALT
hypercholesterolaemia
hypertriglyceridaemia
hyperglycaemia
what findings on urinalysis would be indicative of hyperadrenocorticism?
USG <1.018-1.020
proteinuria
urinary tract infection
how will thyroid hormones appear in cases of cushings?
reduced T4 but nor al TSH (cortisol suppresses T4)
what specific testing can be done for hyperadrenocorticism (cushings)?
low dose dexamethasone suppression test
ACTH stimulation test
urine cortisol creatinine ratio
how is the low dose dexamethasone suppression test carried out?
low dose of dexamethasone (similar to cortisol) blood sample 3 and 8 hours later to measure cortisol, the cortisol should be low and remain low for these 8 hours
(very good sensitivity but low specificity)
how do results of a low dose dexamethasone suppression test vary depending on if the hyperadrenocorticism is pituitary of adrenal dependant?
pituitary - cortisol low at 3 hours but then increases
adrenal - cortisol never drops very low
how is the ACTH stimulation test carried out?
give dog ACTH, this increases cortisol production, then blood sample when administered and an hour later for cortisol
If the adrenal gland is chronically overstimulated then it will be hypertrophied meaning the amount of cortisol produced will be exaggerated
what is done for a urine cortisol creatinine ratio test?
take random samples of urine (this is very sensitive but poorly specific)
what can be done to differentiate between adrenal and pituitary dependant hyperadrenocorticism?
ACTH assay
high dose dexamethasone stimulation test
how is hyperadrenocorticism (cushings) treated?
trilostane
how is response to cushings treatment monitored?
clinical signs
ACTH stimulation testing (3 monthly for first year)
pre-pill cortisol
what are some side effects of using trilostane to treat hyperadrenocorticism?
adrenal necrosis
hypoadrenocorticism
lack of efficacy
vomiting/diarrhoea
what does mitotane do?
kills off adrenal cells (used in hyperadrenocorticism)
when may surgery be indicated for hyperadrenocorticism?
adrenal tumours (not invading major vessels)
pituitary tumours
what is hypoadrenocorticism also known as?
Addisons disease
what is the typical cause of Addisons?
immune destruction of adrenal cortex
(can also be ACTH deficiency due to trauma, tumour…)
what are the typical dogs the present with hypoadrenocorticism?
middle aged female dogs
(poodle, Great Dane, terriers, Nova Scotia duck tolling retriever…)
what are the clinical signs of primary hypoadrenocorticism?
vague…
vomiting (haematemesis), diarrhoea
lethargy
PUPD
abdominal pain
hypovolaemic collapse
(can be acute or chronic)
what hormones can be reduced in Addisons?
lack of cortisol (can’t respond to stressors)
lack of aldosterone (mineralocorticoid)
what are the typical findings of Addisons on a clinical examination?
weak pulse
increased CRT
dehydration
bradycardia
abdominal pain
collapse/syncope
what causes bradycardia in Addisons dogs?
high potassium
what findings on haematology and biochemistry would be indicative of hypoadrenocorticism?
mild non-regenerative anaemia
mild hypercalcaemia
pre-renal azotaemia
lymphocytosis
hyperkalaemia, hyponatraemia
acidosis
what is atypical Addisons?
cortisol deficiency but normal mineralocorticoids (aldosterone)
how can Addisons be tested for?
single cortisol (rules out Addisons if normal)
what is the aim of treating a dog that comes in collapsed with Addisons?
fluid therapy to restore circulating volume
how can hyperkalaemia be treated in hypoadrenocorticism cases?
dextrose saline and insulin (push potassium inside cells)
calcium glutonate (cardioprotectant)
how is chronic hypoadrenocorticism treated?
steroids (dexamethasone, prednisolone…)
DOCP (replace mineralocorticoid)
what are some possible treatment side effects of hypoadrenocorticism?
acute kidney injury
myelinosis (depression, weakness, ataxia)
how can the side effect of myelinosis caused by treating hypoadrenocorticism be minimised?
slowly raise sodium and use dexamethasone (myelinosis is irreversible and often results in euthanasia)
what does a pheochromocytoma do?
adrenal medulla tumour that secretes catecholamines
causes anxiety, tachycardia, tachypnoea, vomiting, hypertension… (these signs are episodic)
