Small animal endocrinopathies 5 Flashcards
Calcium disorders
What are the 2 main differentials for hypercalcaemia in a cat?
- Hypercalcaemia of malignancy
- Idiopathic hypercalcaemia
What is the most common neoplastic cause of hypercalcaemia in cats?
Lymphosarcoma
What group of cats is most at risk of idiopathic hypercalcaemia?
Young to middle aged
How is idiopathic hypercalcaemia diagnosed?
Diagnosis by exclusion, need to rule out everything else
Explain why diagnosis of idiopathic hypercalcaemia can be difficult
- Hypercalcaemia can lead to renal damage (calcium oxalate urolithiasis)
- Can give the impression that the hypercalcaemia is due to chronic kidney disease
When diagnosing the cause of hypercalcaemia, what are the key factors that need to be considered?
- Calcium and phosphate balance: do different things in different diseases
- Hormone balance: also varies depending on disease
What conditions would you be suspicious of in a patient with Severely elevated calcium and moderately low phosphorous?
Primary hyperparathyroidism and hypercalcaemia of malignancy
What conditions would you be suspicious of in a patient with moderately increased calcium and severely increased phosphorous?
Renal failure
What conditions would you be suspicious of in a patient with moderate elevations in calcium and phosphorous?
Vitamin D toxicity and Addison’s
What conditions would you be suspicious of in patient with normal to mildly reduced calcium and moderately elevated phosphorous?
Nutritional secondary hyperparathyroidism
What condition would you be suspicious of with the following hormonal profile: Severely elevated PTH Mild-severely reduced PTHrP Severely elevated ionised calcium Severely elevated vit D
Primary hyperparathyroidism
What condition would you be suspicious of with the following hormonal profile: Mild-severely reduced PTH Severe increase in PTHrP Severely elevated ionised calcium Mild - severely decreased vit D
Lymphosarcoma
What condition would you be suspicious of with the following hormonal profile: Severely elevated PTH Severely elevated PTHrP Severely reduced ionised calcium Mild-severely reduced vit D
Chronic renal falure
What condition would you be suspicious of with the following hormonal profile: Mild-severely reduced PTH Mild-severely elevated PTHrP Mild-severely elevated ionised calcium Mild-severely reduced vit D
Apocrine gland tumours of the anal sac
What condition would you be suspicious of with the following hormonal profile: Mild-severely reduced PTH Mild-severely reduced PTHrP Mild-severely elevated ionised calcium Mild-severely elevated vit D
Hypervitaminosis D
What condition would you be suspicious of with the following hormonal profile:
Mild-severely reduced PTH
Mild-severely reduced ionised calcium
Mild-severely reduced vit D
Hypoparathyroidism
Outline the general management of hypercalcaemia
- May require supportive care until can identify cause
- Active treatment ifc calcium >4.0mmol/L (16.0 mg/dL)
- Treatment depends on magnitude of hypercalcaemia, clinical condition of patient, additional factors e.g. most likely differential and cost, presence of complicating factors e.g. azotaemia, abnormal phosphate levels
List the treatment options for hypercalcaemia
- IV fluids (0.9% saline)
- Diuretics
- Glucocorticoids
- Mithromycin
- Bisphosphonates (pamidronate or zoledronate)
- Most manageed with fluids, diuretics and steroids
Why is the use of fluids or diuretics beneficial in the treatment of hypercalcaemia?
Encourages sodium and calcium loss in the kidney
Why is the use of glucocorticoids beneficial in the treatment of hypercalcaemia?
Decrease absorption of calcium from intestine, reduce bone resorption of calcium, and enhance calcium excretion from kidneys
Why is the use of bisphosphonates beneficial in the treatment of hypercalcaemia?
Inhibit osteoclast resorption of bone (but are not short term drugs)
At what level of hypocalcaemia are clinical signs usuallly detected and what response is required?
<1.5mmol/L, treatment must be initiated as quickly as possible - quick deterioration
What are the clinical signs of hypocalcaemia in dogs and cats?
- Focal muscle spasms/fasciculations
- Ataxia/spasticity
- Tetany and generalised seizures
- Nervousness
- Prolongation of ST segment and QT interval; arrhythmias
- Prolapse of third eyelid (cats)
What is eclampsia?
A manifestation of hypocalaemia, aka puerperal tetany
Describe the clinical features of eclampsia
- Lactation hypocalcaemia
- Plasma calcium <1.5mmol/L
- Most common in small dogs
- Tetany observed
- Fever can develop as muscle contraction generates heat
- Clinical signs depend on rate of decline of serum calcium
- Most comonly in first 21 days of nursing, but report in last 2 weeks of gestation and up to 45 days post whelping
Describe the pathophysiology of eclampsia
- Results from extreme hypocalcaemia in bitches and queens
Describe the aetiology of eclampsia
- Loss of calcium into milk and foetal skeleton
- Poor dietary use of calcium
- Reduced appetite due to stress of parturition
- Parathyroid atrophy poor diet/dietary supplements)
- Hypomagnasaemia
Explain the significance of hypomagnasaemia in eclampsia
- Impact on how effectively hypocalcaemia can be treated and its development
- Cannot measure magnesium in practice but may need to address magnesium concentration to improve calcium uptake and control
When are eclampsia cases most likely to be identified and brought into the practice?
- Seizures/tetany often associated with exercise
- Owner may bring in for another reason and have episode while in waiting room
Describe the treatment approach to an eclampsia episode
- 10% calcium gluconate SLOW IV
- Do not adminster with fluids containing bicarb precursors e.g. Hartmann’s
- 5-15mg/kg IV slow over 10-20 min (equiv. to 0.5-1.5ml/kg), are aiming for calcium above 0.6-0.7mmol/L
- Continue with CRI 2.5-3.75mg/kg/hr of elemental calcium, then review and address cause
What are the presenting features of a dog with pituitary dwarfism?
- Smaller vs litter mates
- Retention of puppy coat
- Metabolism may be non-functional
- Truncal alopecia sparing head and extremities
- hyperpigmentation
- Pyoderma
- Cryptorchidism
- Persistent oestrus
- Proportional dwarfism
Which breed is predisposed to pituitary dwarfism?
GSD
What is the difference between proportional and disproportional dwarfism?
- Proportional: small but in proportion
- Disproportionate: shorter stature than appropriate for heads size
What diagnostic tests are available to differentiate pituitary dwarfism from other disorders causing stunted growth?
- IgF-1 most easily available
- GHRH/clinidine stimulation tests used in research
How does mammary growth hormone relate o the treatment of pituitary dwarfism?
- Current treatment is ingestion of growth hormones
- In metoestrus, high P4 leads to mammary development, leading to release of mammary growth hormone
- Instead of GH injections, injections of progesterone could be used which would induce release of GH from mammary glands into circulation
What is a common consequence of agromegaly and why?
Diabetes mellitus, as growth hormone is a potent insulin antagonist that causes insulin insensitivity
What is acromegaly?
Disorder of growth hormone excess
What are the common causes of acromegaly?
- Pituitary adenoma
- Metoestrus
- Pharmacological action
Compare the prevalence of pituitary adenoma and progesterone as a cause of acromegaly in the dog
- Pituitary adenoma almost unheard of
- Progestone as a a cause: not uncommon in treated animals and animals in metoestrus
Compare the prevalence of pituitary adenoma and progesterone as a cause of acromegaly in the cat
- 15-30% of diabetic cats will have a pituitary adenoma
- Cat mammary tissue keeps GH local, so progesterone is not a cause of acromegaly in cats
What is an unusual clinical feature of poor diabetic control in acromegalic cats compared to cats with poor diabetic control for other reasons?
Poor diabetic control but despite this they maintain or increase body weight - if was due to something other than acromegaly, would expect weight loss
How do dogs and cats differ in the growth hormone response to progesterone?
- In bitches, progesterone stimulates the release of growth hormone from mammary glands, which can then get into systemic circulation
- In cats, this is not possible and GH remains in mammary tissue
What are the treatment options available for a diabetic cat with acromegaly?
- INcreasing insulin dose as required to gain some control (doses of 30-40IU not unheard of)
- More advanced therapies e.g.: somatostatin (expensive), pituitary surgery, pituitary radiotherapy
What is a typical clinical presentation for functional adrenocortical tumours in ferrets?
- > 3yo
- Hair loss
- Vulvar swelling
- Unusual sexual behaviour and aggression
- Difficulty urinating
- Lack of energy (lethargy)
- Muscle atrophy
- Skin disorders and itching
Compare classic hyperadrenocorticism in dogs with the functional adrenal tumours in ferrets
- In ferrets, occurs in oestrus in jills, which will only end if she mates
- Is due to oestrogen toxicity
- Main product of ferret adrenal tumour is adrenal androgens rather than cortisol
What would be the clinical signs in a dog with an adrenal tumour that produced adrenal androgens rather than cortisol?
Very similar to classic hyperadrenocorticism
How could you test for a funtional adrenal tumour in ferrets?
- ACTH stimulation tests, but look for 17-hydroxy progesterone, +/- androstendione and oestradiol
What is the more common product of a functional adrenal tumour in cats?
Aldosterone
What biochemical abnormality and consequently the clinical signs of this change are common in functional adrenal tumours of cats?
- If producing aldosterone mainly, expect hypokalaemia
- Polymyopathy muscle wekaness, ventroflexion of neck
What are the treatment options for an adrenal tumour in ferrets?
- Surgery
- Desorelin (GnRH supeagonist)
What are the treatment options for an adrenal tumour in a dog with progesterone secreting adenoma?
- Surgery
- If not surgery, trolistane (vetoryl): inhibits at lvel of 3hydroxysteroid dehydrogenase
What are the treatment options for an aldosteronoma?
- Surgery
- Or spironolactone (prilictone): aldosterone competitor
What clinical signs would be expected in a dog with phaechromocytoma?
- High levels of adrenaline leading to PUPD, panting, inconsistent hypertension, collapse, dysrhythmia
What are the differentials for a dog presented with PUPD, panting, inconsistent hypertension, collapse, dysrhythmia?
- Phaechromocytoma
- Hyperadrenocorticism
What changes on haematology and biochemistry as a consequence of Cushings would need to be corrected prior to anaesthesia and how?
- Stress leukogram may be seen, no effect on anaesthetic
- High PCV: dehydration, provide fluid therapy
- High liver enzymes on biochem, but ACP does not affect liver as much as A2A would
- Kidney parameters and electrolytes may be altered, corrected with fluid therapy
- Some biochem parameters may indicate acidosis (due to panting), controlled by fluid therapy
