Hyperadrenocorticism Flashcards
Give the medical term for Cushings disease
Hyperadrenocorticism
Describe the two components of the adrenal gland
Cortex - synthesises and secretes steroid hormones
Medulla - synthesises and secretes catecholamines
Which substances are produced in the adrenal cortex?
Mineralocorticoids
Glucocorticoids
Sex hormones and precursors
Describe the production of glucocorticoids
- Secreted by cells in the zona fasciculata under control of ACTH released from the anterior pituitary, itself controlled by CRF released by the hypothalamus.
- Cortisol feeds back negatively on the anterior pituitary and the hypothalamus
What is the role of cortisol?
Involved in homeostasis during stress
List the functions of glucocorticoids
Gluconeogenesis
Glycogen synthesis
Immune/Inflammation suppression
Catabolism (fat and protein degradation)
Inhibition of DNA/protein synthesis
Describe the production/secretion of mineralocorticoids
Secreted by cells of the zona glomerulosa under the influence of angiotension II (and to a lesser extent of ACTH).
Name the main mineralocorticoid and its function
Aldosterone
Retention of sodium and excretion of potassium by the kidney
What are the functions of catecholamines?
Catecholamines stimulate a variety of systems in preparation for fight/flight response thus, effects include increases in heart rate, blood pressure and blood glucose concentration
How is hyperadrenocorticism (Cushings) classified?
Pituitary dependant or Adrenal dependant
Describe pituitary dependant hyperadrenocorticism
Accounts for 80% of cases
It is caused by excessive secretion of ACTH by a pituitary tumour.
This leads to bilateral hyperplasia of the adrenal cortices and excessive cortisol secretion by the adrenal glands.
Most pituitary tumours are adenomas.
Describe adrenal dependant hyperadrenocorticism
Caused by an adrenal tumour, which secretes
excessive amounts of cortisol.
This causes a decrease in ACTH secretion by the pituitary gland and atrophy of the uninvolved adrenal gland.
About 50% of adrenal tumours are adenomas and 50% are adenocarcinomas.
What is the cause of iatrogenic hyperadrenocorticism?
Excessive glucocorticoid administration
Describe the predisposing factors for cushings
Middle aged/older dogs
No sex
Breeds - Poodles, Terriers, Dachshunds, Beagles and Labradors appear to be overrepresented
Rare in cats - but some association with insulin resistant diabetes mellitus
PDH: more common in small breeds
ADH: more common in large breeds
List the common clinical signs of Hyperadrenocorticism
Polydipsia
Polyuria
Polyphagia
Panting
Abdominal distention
Endocrine alopecia
Hepatomegaly
Muscle weakness
Systemic hypertension
List the less common clinical signs of Hyperadrenocorticism
Lethargy
Hyperpigmentation
Comedones
Thin skin
Poor hair regrowth
Urine leakage
Insulin-resistant DM
List the uncommon clinical signs of Hyperadrenocorticism
Thromboembolism
Ligament rupture
Facial nerve palsy
Pseudomyotonia
Testicular atrophy
Persistent anoestrus
Why do animals with Hyperadrenocorticism present with a ‘pot belly’?
This occurs due to weakness of the abdominal muscles
and hepatomegaly - also has thin skin and prominent veins in this region
Where is muscle atrophy most visible in hyperadrenocorticm cases?
Temporal region
Hindlimbs
What is calcinosis cutis?
Large plaques on the skin that can ulcerate and become secondarily infected.
Describe the coat changes seen in hyperadrenocorticism, why do these occur?
Thinning of the hair leading to bilaterally symmetrical alopecia often affecting the ventral abdomen, flanks and neck.
This is because of the inhibitory effect of cortisol on the growth phase of the hair cycle.
Describe the haematology changes seen in hyperadrenocorticism
Neutrophilic leukocytosis
Lymphopenia
Eosinopenia
Thrombocytosis
Mild erythrocytosis
Describe the serum biochemistry changes seen in hyperadrenocorticism
Increased ALKP
Increased ALT - usually mild
Hypercholesterolaemia - raised cholesterol due to lipolysis
Hypertriglyceridaemia
Hyperglycaemia - gluconeogenic effect of steroids
Describe the urinalysis changes seen in hyperadrenocorticism
Specific gravity ≤1.018–1.020
Proteinuria
Urinary tract infection