Endocrine Flashcards
What is the proposed mechanism for PU/PD in feline hyperthyroidism?
Altered renal blood flow
Electrolyte abnormalities
Thyroid hormone excess causing primary polydipsia
Concurrent renal dz?
Methimazole/carbimazole toxicity
Vomiting
Pruritis
Peripheral LN enlargement
Lymphocytosis, eosinophilia, leukopaenia, <5% agranulocytosis, thrombocytopaenia, IMHA
Hepatic toxicity
Increase in ANAs, acquired MG, coagulopathy with normal platelet count
Prognosis hyperthyroidism
Medical management vs I131 tx
MST 2 years vs 2-4 years
Gold standard test for hypothyroidism
TSH response test
No recombinant canine TSH available so have to use human
Hypothyroidism clinical signs
Lethargy
Weight gain
Bradycardia, May worsen DCM
Skin/ coat changes most common (recurrent OE, malassezia, symmetrical slope is)
Reproductive problems
Neurological (diffuse neuropathy, laryngeal paralysis and megaoesophagus - often do not resolve on tx and may be assoc with more generalise myopathy/m.gravis
Dry eye
Lipidosis corneal and retina
Corneal ulceration, uveitis and 2ndary glaucoma
Assoc with Cushings, DM and Addison’s
Congenital: disproportionate growth and puppy coat. Mental retardation
Calcitonin actions
Limits post-prandial hypercalcaemia
Primarily inhibits osteoclasts activity
High doses promote urinary calcium excretion
Calcitriol actions
G-I calcium and phosphorous absorption
Tubular calcium and phosphorous reabsorption
Inhibits further calcitriol production in the kidney
Inhibits PTH
When to use bicarbonate in DKA cases
When pH is less than 7.2 and HCO3 is <12mmol/l despite aggressive fluid therapy and insulin admin
MEq = BW (kg) x 0.4 x (12-HCO3) x 0.5
Five slowly over 6h then check again
Insulin tx in DKA i/m route
0.2mg/kg im once
Continue with 0.1mg/kg im every hour
When bg < 15mmol/l give 0.1mg/kg im q 4 hourly in order to maintain bg stable and avoid hypos
Switch to longer acting when patient stable bright and eating
Insulin for DKA I/v protocol
Prepare 2.2mg/kg soluble insulin in 250mls NaCl 0.9%
Discharge 50ml of this to allow insulin binding to the giving set tubing
Administer solution at 10ml/hr until until Bg <15 then 7ml/hr until bg < 12 then 2-5ml/hr to maintain stable bg
Switch to longer acting when patient stable and eating
Hypoglycaemia Ddx
Lab error Insulinoma Addison’s Sepsis Tumours (hepatocellular carcinoma, mammary carcinoma, haemangiosarc etc) End stage hepatic failure PSS Toy breed and neonate hypoglycaemia Glycogen storage dz Excessive exercise Starvation
Hypoglycaemic crisis - what to do?
Glucose 0.5g/kg IV diluted 1:3 in saline as a slow iv bolus
Continue with CRI or 2.5-5% glucose saline
(Always start low as insulinomad retain the ability to secrete more insulin in response to glucose)
Monitor for hypoxia, cerebral oedema, hyperthermia, lung atelectasis from prolonged recumbency
If failing to respond administer dexamethasone 0.1mg/kg IV
May need sedation w diazepam/pentobarbital in severe cases
In one study a dog was treated with a glucagon CRI and signs resolved in 20mins
Insulinoma medical tx
Prednisolone (start low and work up)
Diazoxide (benzothiazine derivative inhibits insulin secretion and gluconeogenesis) (70% success)
Ocreotide (long acting somatostatin analogue - also inhibits GH and glucagon so can worsen hypoglycaemia)
Streptozocin (nitrosurea antibiotic - toxic to pancreas and metastatic sites but highly nephrotoxic - MSTs similar to controls)
Insulinoma prognosis
785d surgery alone (stage I, stage II 547 and III 217d)
1316d partial pancreatectomy abd preds
12-14months with young dogs having a worse prognosis and clinical stage I having a longer dz-free interval
Stage I - just pancreas
II - pancreas plus node
iii - pancreas plus node and mets (or without node)
Where do insulinomas metastasise to?
Mainly liver, spleen and regional LNs
Rarely lungs
Insulinoma diagnosis
Low glucose with a high or normal insulin
Need abdo ultrasound may see mass but can be nodular
CT may see pancreatic mass (MRI same as CT)
Do 3 view thoracic rads to check for mets
Why do we get hepatomegaly and raised liver enzymes with diabetes mellitus?
Hepatic lipidosis
Supplementation if fluids in DKA
Potassium
Phosphorous if low (can cause haemolysis) - half of potassium can be given as potassium phosphate
Magnesium
Possibly bicarbonate but unlikely
Treatment of acromegaly
Radiotherapy
Transphenoidal hypophysectomy
Ocreotide (somatostatin analogue) - moderately successful in cats
Long acting insulin with short acting insulin around meal times for insulin resistant DM
Diagnosis of acromegaly
CT showing pituitary mass
High ilgf-1 can support a diagnosis
Causes of central diabetes insipidus
Intracranial tumours Metastatic neoplasia Inflammatory dz Parasites Pituitary surgery Severe head trauma Idiopathic (rare)
Causes of acquired nephrogenic diabetes insipidus
And pathophysiology of these
Metabolic (hypokalaemia - downregulates aquaporin 2), hypercalcaemia)
Drugs (lithium, chemotherapy)
Urethral obstruction
Kidney failure
Paraneoplastic syndrome (only leiomyosarcoma)
Hyperthyroidism - increased blood flow to kidney
Pyelonephritis
Addison’s - sodium depleted so can’t generate concentrated renal medullary interstitium
Liver failure - reduced urea
Pyometra
Cushings - reduced release and Action of ADH
Acromegaly - DM or glomerulopathy
Hypercalcaemia - interferes with proper functioning of renal tubular cells that normally respond to ADH
When to stop phase 2 of a water deprivation test
If the patient is
- dull or clinically dehydrated
- has lost >5% BW
- is azotaemic
- is hypernatraemic
- USG >1.030
Then obtain urine, bloods, measure USG and urine osmolality
Phase 1 of modified water deprivation test
Determine water intake at home
Gradually decrease water intake at home over 3-5 days until having 100mlKg/day or becoming lethargic or aggressively seeking water
Divide daily water portions into multiple small portions
Withhold food for 12 hours before phase 2
Phase 2 of the MWDT
Withhold food and water, empty bladder, check USG and urine osmolality, weigh patient, check BUN/crea and electrolytes
Check clinical signs, weigh and check urine every 1-2 hours
Bloods every 2-6 hours
Phase 3 MWDT
Administer exogenous ADH if Urine has not yet concentrated
IM - monitor USG every 30 mins for up to two hours
Conjunctival - monitor every 1-2 hours for 8-12 hours
SQ - every 1-2 hours for 8-12 hours
Phase four MDWT
Offer small amounts of food and water every 20-30 mins for 2 hours
Monitor signs and return to free choice water when patient clinically normal
Interpretation of MDWT
USG >1.030 after phase 1 or 2= primary polydipsia
<1.008 after phase 2 = complete CDI or congenital NDI
USG after phase 3 >1.015 = CDI
<1.008 after phase 3 = congenital NDI
USG 1.008-1.020 after phase 2 = acquired NDI or partial CDI progress to phase three and if osmolality increases by 10-15% = CDI
Osmolality = 36 x USG (1.010 = 360)
Treatment of diabetes insipidus
One drop DDAVP in conjunctival sac
If NDI - hydrochlorthiazide and low sodium diet (reduced stimulation of thirst centre and water intake - reducing urine volume)
DDx PUPD
Central DI/ nephrogenic DI renal failure Cushings Addison’s Liver failure Hypercalcaemia Pyometra Septicaemia Hypercalcaemia Hyperthyroidism Hypokalaemia Acromegaly Very low protein diet Primary hyperaldosteronism fanconis syndrome Primary renal glycosuria Diabetes mellitus Post-obstructive diuresis Glucocorticoids Diuretics Phenobarbitone High salt diet Levothyroxine Vitamin D Primary polydipsia Renal medullary washout Bacterial pyelonephritis
Osmotic diuresis causes of PUPD
DM Fanconis Primary renal glucosuria Renal failure Post obstructive diuresis
DDx hypercalcaemia
Primary hyperparathyroidism Renal secondary hyperparathyroidism Nutritional secondary hyperparathyroidism Vitamin D toxicity Malignancy (lymphoma, AGA, myeloma) Addison’s Young growing animal Granulomatous dz Non-malignant skeletal dz Lab error (Hyperalbuminaemia) Hyperthyroidism Grape toxicity
Treatment of primary polydipsia
Reduce water intake by 10% each week
Increase exercise, add another pet, increase human contact, provide a distraction eg radio
Most common cause of feline hypercortisolism (Cushings)
Pituitary corticotropin secreting tumour (80%)
Rest are cortisol secreting adrenal tumours (50% malignant)
Preferred tests for Cushings in cats
LDDST
UCCR
Treatment of feline primary hyperaldosteronism
Adrenalectomy
Medical management:
Potassium gluconate
Spironolactone
Amlodipine
Treatment of pituitary dwarfism
Porcine growth hormone injections
Medroxyprogesterone acetate to stimulate mammary GH production as well as proligestone (should spay before to prevent pyometra)
If concurrent hypothyroidism May need levothyroxine
Hypocalcaemia clinical signs
Tetany, seizures, tremors, fasciculations, weakness/ataxia(less common),
Earlier signs: facial pawing, anxiety, aggression due to muscle pain,
Cataracts: immature, cortical, punctate and diffuse (characteristic of hypoparathyroidism hypocalcaemia)
Treatment of hypoparathyroidism
Calcium and vitamin D supplement (needed for GI absorption Ca)
Can eventually stop calcium and only give vitamin D (calcitriol and alfacidiol as these are hydroxylated forms)
In emergency iv calcium gluconate 0.5-1.5mlKg IV over 10-30 minutes. Must monitor ECG for bradycardia, shortened QT interval. Risk for cardiac arrest. If vomiting stop or slow infusion
Maintenance 60-90mg/kg/day do not add to lactate containing fluids as it can precipitate and don’t mix calcium and bicarbonate
Can give calcium gluconate 1:1 w saline s/c q6-8 hours too after tetany has resolved and this may be easier whilst awaiting oral vitamin D to take effect
Should check magnesium levels because if low hypocalcaemia can be refractory to tx
DDx for Na:K < 27
Renal/ urinary Tract dz Addison’s Severe GI disease Parasites Hepatic failure Effusions Pregnancy DM Drug induced Other - repercussion injury/haemolysis
If <24 highly specific for Addison’s
Tx acute Addisonian crisis
Fluids 20-30ml/kg/hr saline
Give Dex if in shock
Perform ACTH stim
If not yet had dex now give dex or hydrocortisone
Once fluid balance improved give hyrocortisone sodium succinate (dex has no mineralocorticoid activity) 0.5-0.625mg/kg/h CRI
If acidotic and PH <7.2 May require bicarbonate
Tx of hyperkalaemia in acute addisonian crisis
Most important tx is IV fluids
Glucose IV
0.2iu/kg soluble insulin IV and dextrose 2g/unit of insulin (always measure BG after administration)
Calcium gluconate 10% slowly IV monitoring ECG
Prognosis of hyperaldosteronism (Conns)
Medical tx - 7 months - 984 days
Post-adrenalectomy - good 50% Alive one year post-op but surgical mortality is high
Protracted survival post-op if tumour is a carcinoma cf Adenoma
Best test for discriminating PDH from ADH (cushings) in cats
Measure ACTH levels - very sensitive and specific but difficult to do
Better than high dose dex
Differences between canine and feline HAC
Cats don’t have low urine specific gravity despite PU/PD
ALP is often low
Clinical signs of hypercalcaemia
PUPD Anorexia Dehydration Lethargy Weakness Vomiting Pre-renal azotaemia Chronic renal failure (mineralisation likely if phos x tCa = > 5)
Constipation Cardiac arrhythmia Seizures or twitching Death Acute renal failure Calcium urolithiasis
Treatment of hypercalcaemia in an emergency
Saline 3x maintenance Furosemide once rehydrated Calcitonin (acts for around two days) Bisphosphonates Glucocorticoids (once diagnosis is reached) Bicarbonate if acidotic
If idiopathic often responds to high fibre diet +/- steroids
Hypocalcaemia DDx
Parathyroid disorders:
Primary hypoparathyroidism
Or secondary to trauma/surgery
Vitamin D disorders:
Acute/chronic renal, Nutritional secondary hyperparathyroidism
Redistribution disorders: Puerperal tetany (eclampsia) Feline urt obstruction Sodium phosphate enemas Alkalinizing therapy Massive blood transfusion (excess of citrate products) Furosemide Ethylene glycol intoxication Pancreatitis
Acute renal failure - massive increase in phosphate lowering calcium
Side effects of bisphosphonates
Nausea Vomiting Reflux and oesophagitis Abdominal pain Dyspesia Hypocalcaemia Hypophosphataemia Hypomagnesaemia Hypokalaemia Cost and availability
Thyroid carcinoma complications and MSTs
Megaoesophagus, laryngeal paralysis, haemorrhage, horners syndrome
MST 3 years if mobile and 6-12 months if fixed
When to use chemo for thyroid carcinoma
Animals with documented mets or tumours greater than 27cm^3
What level are fructosamines if there is a somogyi effect
They are usually high
Complications with surgical treatment of insulinoma
Pancreatitis, thromboembolic dz and arrhythmias
