Adrenal Pathology I Flashcards
What does the zona glomerulosa secrete?
Mineralcorticoids (Aldosterone)
What stimulates the secretion of mineralcorticoids from the zona glomerulosa?
Angiotensin II and increased extracellular K+ concentration
What is the function of the zona fasciculata?
To produce glucocorticoids such as cortisol
not required for survival
What is the effect of cortisol?
- Induces glucose production
- Supresses inflammation and immune responses
- Inhibits wound healing
What is the function of the zona reticularis?
- Produces adrenal sex hormones
- Only has a minor physiological difference
What is the medulla responsible for?
responsible for systemic secretion of the catecholamines
‘fight or flight’ response, increased heart rate, and blood pressure (hyperglycaemia)
adrenal medulla is not required for survival
what is adrenal agenesis
rare condition where the adrenals fail to develop, can be either bilateral or unilateral
occurs to accesory adrenal tissue
commonly perirenal or within the testicular sheath/ incidental
what is the blood circulation of the adrenal glands
- sinusoidal plexus through the cortex and medulla
- fragile and susceptible to death
- causes extertional deaths in racehorses
what is Waterhouse-Friderichsen syndrome
group of conditions where the adrenals fail to function effectively- occurs as a result of bleeding into the glands
What is WFS an expression of in septicaemic cows?
DIC (Haemorrhagic adrenal necrosis)
What is adrenalitis?
Inflammation of one or both of the adrenal glands
either infectious or autoimmune
What two things can cause adrenal toxicity?
- Mitotane- directly cytotoxic to adrenocortical cells
- Trilostane
In what animals is adrenocortical hyperplasia common in?
due to sustained physiological stress
Common in old dogs, cats and horses
What may adrenocortical hyperplasia represnt?
Hyperadrenocorticism
* sustained physiological stress
* sometimes idiopathic and incidental
What is an adrenal cortical adenoma?
- benign neoplasm
- common in older dogs
- well-defined encapsulated nodule that compresses or distorts the surrounding tissue
- may be functional or non-functional
What animals are affected by an adrenal cortical carcinoma?
- Older dogs and cattle
- large, poorly defined, may efface normal tissue
- vascular invasion and thrombosis
- may result in haemoabdomen
- metastatsize widely
- can be functional or non-functional
What three conditions are examples of hormonal excess?
- Hyperadrenocorticism -> excess cortisol
- Atypical hyperadrenocorticism
- Hyperaldosteronism
What condition is an example of hormonal deficiency?
Hypoadrenocorticism (addisons disease)
What are the four forms of hyperadrenocorticism?
- Pituitary-dependnent
- Adrenal-dependent
- Iatrogenic
- Ectopic ACTH secretion
What is pituitary-dependent hyperadrenocorticism?
- Pituitary tumour secretes ACTH
- Unresponsive to cortisol feedback
What is adrenal-dependent hyperadrenocorticism?
Adenal neoplasm secretes excess cortisol independent of the ACTH
What is iatogenic hyperadrenocorticism?
administration of chronic, high-dose corticosteroids
What is Ectopic Hyperadrenocorticism?
Secretion of ACTH by non-pituitary neoplasms
What are the clinical signs of excess cortisol (hyperadrenocorticism)
- Stress
- Hair loss
- Weight gain/ Getting fat
- Blood glucose increase
- Supressed immune system
What does the skin look like in an animal with hyperadrenocorticism?
- Alopecia in the pressure points (keratin plugs)
- Dermal atrophy- thin fragile skin, poor wound healing
- Hyperpigmentation (excess ACTH secretion)
What is calcinosis cutis?
Calcification of degenerate collagen
other organs may also mineralise
What does hyperadrenocorticism look like in terms of muscle?
- Abdominal and limb muscle atrophy
- ‘pot-belly’ appearance
What is a steroid hepatopathy?
- Diffusely enlarged pale liver
- Midzonal glycogen storage within hepatocytes causing a ‘pot-belly’ appearance
Why does hyperadrenocorticism cause polyuria and polyphagia?
- Cortisol causes a decreased sensitivity to ADH
- Polyphagia may be exaccerbated by diabetes mellitus (direct effect of cortisol only seen in dogs)
What does hyperadrenocorticism look like in cats?
- rare and mostly pituitary dependent
- thin fragile skin
- curled pinna
What does hyperadrenocorticism look like in ferrets?
- excess production of sex hormones such as oestrogens and androgens
- usually occurs around middle age (3/4)
- adrenal disease may be related to neutering
What are the clinical signs of hyperadrenocorticism in ferrets?
- Hair loss that begins in the tail and then progresses towards the front until the ferret is completely bald
- Symmetrical
- All the clinical signs are related to the duration and severity of sex steroid excess
What swollen organ is common in ferrets with hyperadrenocorticism?
- Swollen vulva in spayed females
- Straining to urinate due to an enlarged prostate
- thinning of skin, muscle wasting, and pot-belly appearance in long term disease
What three types of hypoadrenocorticism are there?
- Primary
- Secondary
- Iatrogenic
What does primary hypoadrenocorticism look like?
Most commonly an immune related destruction
related to adrenal destruction due to inflammation, neoplasia, haemorrhage, infarction or toxicity
affects the entire cortex (glucocorticoid and mineralcorticoid deficiency)
What causes secondary hypoadrenocorticism?
- Inadequate ACTH secretion
- Zona glomerulosa unaffected (only glucocorticoid deficiency)
What causes iatrogenic hypoadrenocorticism?
- Sudden discontinuation of corticosteroid therapy
- temporary disease due to supression of ACTH secretion
- only a glucocorticoid deficiency
What is primary hyperaldosteronism (Conn’s syndrome)
- Rare condition
- Aldosterone producing adenoma
What is secondary hyperaldosteronism?
Renin-angiotensin system activation due to chronic systemic
circulatory impairment (eg. right-sided heart failure)
What is pheochromocytoma?
Neoplasia of the adrenal medulla
Dark- Colour-Tumour
Why does Hyperadrenocorticism cause polyuria?
Cortisol decreases the sensitivity to ADH
What is the effect of aldosterone on the renal tubules?
- Increased Na+ excretion
- Increased K+ excretion
How does stress trigger glucocorticoids?
- Stress = CRH from hypothalamus = ACTH from anterior pituitary = glucocortcoids from adrenal cortex
What may adrenal haemorrhage cause?
- Exertional deaths in race horses
- Neonates/a bortion
- DIC
- septiceamia
What is WFS an expression of in cows?
DIC in septicaemic cows= haemorrhagic adrenal necrosis
What does excess ACTH secretion cause hyperstimulation of?
Pituitary dependent hyperadrenocorticism
The adrenal cortices and bilateral hyperplasia
What does an adrenal dependent hyperadrenocorticism cause hypersecretion of?
- Hypersecretion of cortisol by a functional adrenocortical tumour, excess cortisol suppresses ACTH secretion, resulting in a bilateral adrenocortical atrophy
cortisol promotes…
What is the mechanism of steroid hepatopathy?
- Cortisol promotes hepatic glycogenesis to remove excess glucose
What can hyperadrenocorticism go on to cause?
Hyperglycaemia -> insulin antagonism and gluconeogenesis
* Predisposes to diabetes mellitus
Immunosuppression
* secondary infections in the skin/ urinary tract
Predisposed to vascular thrombosis and gall baldder mucocele
What cell changes are induced by corticosteroid release?
- Lymphpenia, eosinopenia
- Monocytosis and neutrophillia
What are the 4 things that occur with hypoaldosteronism?
- Hyponatremia
- Increased water excretion
- Hyperkalaemia
- Acidosis
What may a pheochromocytoma cause?
- May secrete catecholamines (adrenaline and noradrenaline)
- Hypertension-> spontaneous haemorrhage
- Tachycardia
- Cardiac hypertrophy
- Hyperexcitability
