Endocrine Flashcards
Thyroid action
Increases metabolism
Hyperthyroidism in dogs
Rare
Nutritional hypertyroidism (fresh thyroid given in raw feeding)
What causes this change in appearance?
Hyperthyroidism
Thyroid crisis
Severe tachycardia (>300bpm), tachypnoea, panting, respiratory distress, profound weakness, ventro-flexion, sudden blindness due to hypertension
What form of hyperthyroidism can cause poor appetite?
Apathetic hyperthyroidism/apathetic thyrotoxicosis
How does mild thyroid disease affect kidney parameters?
Improve mild kidney disease
Best initial test for hyperthyroidism
Total T4 (high TT4 and CS = diagnosis)
Follow up tests if TT4 is negative but there are clinical signs suggestive of hyperthyroidism
Free T4 and TSH
How can euthyroid sick syndrome be ruled out (non-thyroidal disease affecting thyroid hormone levels)?
Scintigraphy
Treatment of feline hyperthyroidism
Radioactive iodine (131 I), SC injection
Surgery (thyroidectomy)
Anti-thyroid medication (carbimazole ‘pro-drug’/methimazole, stop incorporation of iodine into protein associated with thyroid hormone)
Ultra-low iodine diet
Monitoring of hyperthyroidism that is non-negotiable in all cases
Clinical exam (BCS, MCS, fundic exam and blood pressure)
Weight check
Nutritional assessment
What hormones are produced by the adrenal medulla?
Catecholamines
What hormones are produced by the adrenal cortex?
Zona reticulus: androgens
Zona fasciculata: glucocorticoids
Zona glomerulosa: mineralocorticoids
Pituitary adrenal axis
Pituitary dependent hyperadrenocorticism
80-90%
Micro and macro adenomas/adenocarcinomas
Adrenal dependent hyperadrenocorticism
10-20%
Functional adrenal adenomas and carcinomas (50:50)
Iatrogenic hyperadrenocorticism
Exogenous steroids
Presentation in hyperadrenocorticism
Middle aged to old dogs
Females > males
PUPD (secondary diabetes insipidus)
Polyphagia
Muscle wasting/weakness/pot belly/panting
Skin thinning/calcinosis cutis/pigmentation/bruising
Symmetrical hair loss
Reproductive dysfunction
Abdominal radiograph findings with hyperadrenocorticism
Hepatomegaly
Pot-bellied appearance
Calcinosis cutis
Distended bladder
Thoracic radiograph findings with hyperadrenocorticism
Tracheal and bronchial wall mineralisation
Pulmonary metastasis
Osteoporosis
Haematology findings in hyperadrenocorticism
Stress leukogram (neutrophilia: mature, lymphopaenia, monocytosis, absolute eosinopaenia)
Clinical chemistry in hyperadrenocorticism
Increased ALP (steroid induced isoform)
Increased ALT (‘steroid hepatopathy’)
Hyperglycaemia
Increased cholesterol and triglyceride
Mildly abnormal bile acids
Urinalysis findings in hyperadrenocorticism
USG <1.030, mild dehydration
Mild glucosuria
Proteinuria
Positive urine culture (reduced immune function/glucosuria)
Diagnostic tests for hyperadrenocorticism
Low dose dexamethasone (3 samples at 0, 3-6, 8h)
ACTH response (samples at 0 and 1h)
Urinary cortisol:creatinine ratio (morning urine sample)
Steroid induced alkaline phosphatase
Meaning of positive response to low-dose dexamethasone
Pituitary dependent hyperadrenocorticism
When should you test for hyperadrenocorticism?
Dog in which you could believe a positive result
Treatment of hyperadrenocorticism
Medical: Trilostane (licenced)
Surgical: adrenalectomy for ADH, hypophysectomy for PDH
What adrenal medulla condition may be confused with hyperadrenocorticism?
Phaeochromocytoma
Treatment of phaeochromocytoma
Surgical
Medical: adrenoreceptor antagonists (sympatholytics), phenoxylbenzamine (alpha), propanolol (beta)
Activated calcium
Calcitriol
Effect of parathyroid hormone on blood calcium
Increase (from various sources)
Reasons for false high calcium result
Lipaemia
Icterus (jaundice)
Haemolysis
Effect of hypoalbuminaemia on calcium
Low (calcium binds to albumin)
Mechanism of renal secondary hyperparathyroidism
Renal disease affects phosphate levels = high/low total Calcium (PTH restoring balance?)
Effect of hyperphosphataemia on calcium
Increased complex fraction
Affect of high calcium/phosphorous
Mineralisation of tissues e.g. kidneys, gastric mucosa (high levels complex/precipitate)
Causes of hypercalcaemia
HOGSINYARD
Hyperparathyroidism
Osteolysis
Granulomatous disease
Spurious (albumin)
Idiopathic
Neoplasia
Young
Addison’s
Renal disease (total Ca in horses)/Raisin toxicity
D (Vit. D) toxicity
Most common causes of hypercalcaemia in dogs in practice
Malignancy
Hypoadrenocorticism
Primary hyperparathyroidism
Chronic renal failure
Vitamin D toxicosis
Granulomatous disease
Most common causes of hyperparathyroidism in cats
Idiopathic hypercalcaemia
Renal failure (total mainly, occasionally iCa)
Malignancy (lymphoma and squamous cell carcinoma)
Primary hyperparathyroidism
Test to differentiate PTH dependent/independent hypercalcaemia
PTH and iCa
When is parathyroid related peptide/PTHrP present?
Humoral hypercalcaemia of malignancy
Treatment of hypercalcaemia
Stabilise calcium urgently: fluids/diuresis, glucocorticoids, bisphosphonates
Treatment of cause
Causes of hypocalcaemia
Parathyroid dependent/primary hypoparathyroidism (spontaneous immune mediated, functional hypomagnesaemic, post-surgical)
Demand exceeds supply/mobilisation (periparturient tetany/eclampsia, nutritional deficiency of calcium/Vit. D, pancreatitis)
(PTH and Calcitriol resistance syndromes)
How do hypocalcaemia cases present?
‘Rubbing face’
(Neuromuscular excitability, agitation)
Short term therapy/management of hypocalcaemia
IV calcium (gluconate, borogluconate, chloride)
Monitor for bradycardia
Long term therapy for hypocalcaemia
Aim for subclinical/low normal
Oral calcium supplement
Vitamin D to promote calcium uptake (calcitriol short term, alfacidol/dihydrotachysterol long term)
Type 1 like diabetes in dogs
Insulin deficiency
Common: immune mediated (antibodies in circulation against islet Ag) or B loss due to EPI/pancreatitis
Rare: congenital B loss
Type 2 like diabetes in dogs
Insulin resistant
Common: progesterone (metestrus), acromegaly, hyperadrenocorticism, exogenous corticosteroids
Rare: IGF-1/GH excess (pituitary acromegaly)
Causes of type 1 diabetes in dogs
Pancreatectomy
Pancreatitis
Auto-immunity
Islet cell hypoplasia
Chemical toxicity
Causes of type 2 diabetes in dogs
Progesterone/agen
Growth hormone
Glucocorticoids
Glucagon
Catecholamines
Thyroid
Obesity
Are most diabetic dogs insulin dependent or not?
Insulin dependent
(Exceptions are bitches in metoestrus and dogs with concurrent Cushings may/may not be)
Clinical presentation of diabetes mellitus in dogs
Older dogs (7-9y)
Female > male
‘Starvation amidst plenty’ (polyphagia but losing weight)
PUPD
Quickly tired
Diabetic cataracts
Recurrent infections (e.g. UTI)
‘Acetone’ breath
Diabetic ketoacidosis
Acute
Dull, depressed, weak, comatose?
Vomiting
Dehydrated
IVFT/critical care
Monitoring diabetes mellitus in dogs
Blood glucose curves (can be done at home)
Fructosamine (non-enzymatic binding of glucose to albumin)
Glycated haemoglobin (glucose non-enzymatically bound to Hb)
Urine testing
Somogyi
Low blood sugar (hypoglycemia) episode leads to high blood sugar (hyperglycemia) due to surge of hormones
Complications of insulin treatment of dogs with diabetes mellitus
Hypoglycaemia
Pancreatitis
Keratoconjunctivitis
Cirrhosis
Neuropathy
Treatment of canine diabetes
Daily routine of insulin injection, food and exercise (all at the same time)
Pathophysiology of ketoacidosis
Reduced insulin > reduced glucose uptake into cells > metabolic deficit
Glucagon > lipolysis > fatty acids > acetyl coA > ketones (acetoacetate, b-hydroxybutyrate, acetone)
Acetoacetate and b-hydroxybutyrate acidic > metabolic acidosis > inappetence, nausea, reduced mentation, vomiting > dehydration, renal hypoperfusion and electrolyte derangements > death
Diagnosis of ketoacidosis
b-hydroxybutyrate (most abundant blood ketone)
Blood gas (metabolic acidosis)
Stabilisation of patient with ketoacidosis
Hartmann’s (monitor electrolytes closely, dehydration may cause pseudohyperkalaemia which is actually hypokalaemia, insulin therapy may drive K+ into cells)
Electrolytes (potassium supplementation, rarely potassium phosphate for hypophosphataemia, correct glucose for hyponatraemia, correct hypocalcaemia if clinical sign, magnesium supplementation if not doing well)
Analgesia (headache?)
Anti-emetics (nausea)
Concurrent disease
Hyperglycaemic hyperosmolar syndrome
Rare
Pathogenesis similar to DKA but a small amount of insulin and hepatic glucagon resistance reduces lipolysis so ketones not elevated
Diagnosis: BG >33mmol/L, no urinary ketones, serum osmolality >350mOsm/kg
Treatment: fluid therapy, insulin therapy when normovolaemic
Glucose monitoring in DKA patient
Blood sampling by central venous catheter
Freestyle Libra (easy to place, monitor via app, interstitial not blood)
Signalment for diabetes mellitus in cats
> 7y
M/MN>F/FN
Obese
Treatment with glucocorticoids or progestagens
Clinical signs of diabetes mellitus in cats
PUPD
Weight loss
Lethargy
Polyphagia
Less common: weakness, plantigrade stance, ventroflexion of neck, depression/anorexia (DKA)
If a cat with diabetes mellitus has abdominal pain what might you suspect?
Pancreatitis (triaditis?)
Type I diabetes in cats
Deficiency of insulin (pancreatic b cell loss)
Causes of b cell loss/destruction
Chronic pancreatitis
+/- EPI
Pancreatic amyloidosis
Glucose toxicity
Immune mediated disease
Congenital lack of b cells
Type 2 diabetes in cats
Inability to respond to insulin (usually have functioning b cells at time of diagnosis)
+/- relative insulin deficiency
How does glucose toxicity lead to insulin dependent diabetes mellitus?
Diagnostic plan for a cat with suspected diabetes mellitus
Document persistent hyperglycaemia and glucosuria (rule out stress hyperglycaemia) and appropriate clinical signs
Fructosamine
Irreversible reaction between glucose and plasma proteins
Indicates average BG during preceding 1-3 weeks
Diabetic cat diet
High protein (gluconeogenesis provides consistent energy source)
Restricted carbohydrate (relieve hyperglycaemia/glucose toxicity)
Wet formulation (improves satiety and maintains hydration)
Can graze but don’t exceed daily calories (weight loss)
Insulin products
Lente insulin
Protamine zinc insulin
(Glargine)
(Detemir)
Last resort for diabetes mellitus treatment in cats if owners will not consider insulin treatment
Glipizide
Bexagliflozin (sodium-glucose cotransporter 2 inhibitor)
Causes of unstable diabetes in cats
Compliance issues
UTI (may have no clinical signs)
Pancreatitis
Significant dental disease
Insulin resistance
No response to insuline at a dose of >2.2IU/kg/dose
Hypoglycaemia
BG <3-3.5mmol/l
Mild hypoglycaemia well tolerated, severe hypoglycaemia is life threatening
Clinical signs of hypoglycaemia
Lethargy
Muscle tremors
Anorexia and vomiting
Ataxia
Recumbency
Vocalisation
Seizures
Treatment of hypoglycaemia
At home: honey/glucose on oral mucous membranes/feed
Clinic: 25% dextrose solution slow IV, 5% dextrose CRI
Monitor clinical signs and blood glucose
Biochemistry parameters raised in renal failure
Urea
Creatinine
Electrolyte abnormality associated with refeeding syndrome
Hypophosphataemia
Electrolyte abnormality associated with hypervitaminosis D
Hyperphosphataemia
Treatment of inadequate hormone production from the zona glomerulosa of adrenal gland (in hypoadrenocorticism)
Fludrocortisone
