Endocrinology (1-8) Flashcards
what hormone is produced in the largest amount by the thyroid gland?
thyroxine (T4)
what hormone stimulates T4 production by the thyroid?
TSH
(thyroid stimulating hormone)
what is the major active Thyroid hormone?
T3
name the thyroid hormone
99% protein bound in the blood;
protein bound form acts as a reservoir to maintain steady state concentration of free form
T4
where is the majority of T3 derived from?
extrathyroidal enzymatic deiodination of T4
name the site of pathology in primary hypothyroidism
thyroid
(common)
name the site of pathology in secondary hypothyroidism
pituitary
(very rare)
name the site of pathology in tertiary hypothyroidism
hypothalamus
(very very rare)
name 3 causes of primary acquired hypothyroidism in dogs
- Lymphocytic thyroiditis (autoimmune)
- idiopathic follicular atrophy
- neoplasia
name 3 dog breeds with an increased risk of primary acquired hypothyroidism
- boxers
- dobermann pinscher
- border terrier
name 3 dog breeds with a decreased risk of primary acquired hypothyroidism
- frenchies
- yorkies
- pugs
what are the two main categories of clinical signs for primary acquired hypothyroidism in dogs
- metabolic
- dermatological
name 3 metabolic clinical signs of primary acquired hypothyroidism in dogs
- lethargy
- weight gain
- exercise intolerance
(NOT PU/PD)
name 5 dermatological clinical signs of primary acquired hypothyroidism in dogs
- alopecia
- pyoderma
- seborrhea
- dry/poor quality coat
- hyperpigmentation
name a consistent change on serum biochemistry that is seen with primary acquired hypothyroidism in dogs
increased lipids
(triglycerides and cholesterol)
what clinical sign to the following Ddx have in common?
- hypothyroidism
- hyperadrenocorticism
- Diabetes mellitus
- pancreatitis
- cholestasis
- hepatic insufficiency
- protein-losing enteropathy
hyperlipidaemia
name the endocrine test
very good initial screen for hypothyroidism in patients with compatible clinical signs;
if normal, hypothyroidism is effectively ruled out;
may be falsely elevated in dogs with anti-antibodies;
sighthounds have a lower amount
TT4
(total T4)
name the drug
can cause disturbed thyroid function
Trimethoprim-sulfonamides
name the drug
can alter T4 and TSH concentrations;
T4 significantly decr & TSH significantly increased
Phenobarbitone
name the drug
can alter T4 and TSH concentrations;
can decr. T4 with normal TSH
glucocorticoids
name the cause of low TT4
in response to almost any systemic illness, surgery or trauma:
* body decr. TSH & therefore signal for T4 release
* physiologic adaptation that decr. cellular metabolism during illness
low TT4 and normal TSH
sick euthyroid
name the endocrine test
50% of hypothyroid dogs are positive for this;
these are found in dogs with lymphocytic thyroiditis
TgAA
(thyro-globulin auto-antibodies)
what is the treatment of choice for dogs with primary acquired hypothyroidism?
Levothyroxine
(0.02-0.04 mg/kg PO q12/24h)
when should the TT4 concentrations and clinical signs be checked to assess the response of a dog with hypothyroidism to Levothyroxine treatment?
4-8 weeks after starting meds;
4-6 h after giving med in morning
name 3 clinical signs of feline hyperthyroidism
- weight loss
- increased appetite
- PU/PD
name 3 clinical signs for a cat with apethetic hyperthyroidism (~10% of cases)
- decr. appetite
- lethargic
- weakness
what should be palpable on physical exam of a cat with hyperthyroidism (in 80-95% of cases)
palpable goitre
name 3 differential diagnoses for feline hyperthyroidism
- chronic kidney disease
- Diabetes mellitus
- primary cardiac disease
name the concurrent disease that may develop when treating incr. T4 (feline hyperthyroidism)
chronic kidney disease
how to confirm hyperthyroidism in a cat?
total T4
name 2 medication options for medical management of feline hyperthyroidism
- Methimazole (Thiamazole)
- Carbimazole (methimazole in vivo)
name the 4 long term management options for feline hyperthyroidism
- medical management
- dietary management
- surgical thyroidectomy
- radioactive iodine
(3 & 4 are curative, 1 & 2 not)
how often is on-going monitoring of a cat being/was treated for hyperthyroidism recommended
every 3-6 months
name 4 possible complications of a thyroidectomy
- recurrence
- laryngeal paralysis
- hypocalcaemia (hypoparathyroidism)
- hypothyroidism
what to supplement for hypoparathyroidism following thyroidectomy?
calcium + vitamin D supplementation
name the 3 forms that calcium is found in within the plasma
- physiologically active ionised form (50%)
- chelated form (10%)
- protein bound form (40%)
what 3 things can the chelated form of calcium be complexed with in plasma
- lactate
- citrate
- bicarbonate
name the hormone
increases renal absorption of calcium;
causes osteoclasts to release calcium from the skeleton
parathyroid hormone (PTH)
name the hormone
secreted by the thyroid gland;
decreases bone resorption and lowers calcium concentration
calcitonin
name the regulator of calcium
increases calcium absorption from the intestines;
has effects on bone and kidney to increase calcium levels;
formed by successive hydroxylation in the liver and kidneys
1,25 dihydroxyvitamin D
(1,25 Vit D)
why is polyuria and polydipsia seen with hypercalcaemia?
due to ADH inhibition
name the 2 most common neoplastic causes of hypercalcaemia in dogs
- anal sac adenocarcinoma
- lymphoma (LSA)
name 4 common causes of hypercalcaemia in dogs
- neoplasia
- renal disease
- hypoadrenocorticism
- parathyroid disease
name 3 common causes of hypercalcaemia in cats
- idiopathic (50%)
- neoplasia
- renal disease
name the cause of hypercalcaemia
often present with tenesmus, rectal mass, anorexia, PU/PD, lethargy;
tends to metastases early
anal sac adenocarcinoma
name 3 treatment options if the calcium is high in an emergency situation
- IV fluid to promote calciuresis
- furosemide once hydrated
- bisphosphonates (inhibit osteoclasts)
name the 6 most common causes of hypocalcaemia
- hypoalbuminaemia
- chronic renal failure
- pancreatitis
- eclampsia
- idiopathic or iatrogenic hypoparathyroidism
- protein losing enteropathies
name the 3 parts of the adrenal cortex
- zona glomerulosa
- zona fasiculata
- zona reticularis
where are mineralocorticoids (aldosterone) produced within the adrenal cortex
zona glomerulosa
where are glucocorticoids (cortisol) produced within the adrenal cortex
zona fasiculata
where are sex hormones (androgens) produced within the adrenal cortex
zona reticularis
where are catecholamines (adrenaline and noradrenaline) produced in the adrenal gland?
adrenal medulla
name the disease
syndrome caused by excessive amounts of glucocorticoids in the body
hyperadrenocorticism
(Cushing’s Syndrome)
what 3 specific tests should be done to screen for hyperadrenocorticism
- urine cortisol:creatinine ratio
- ACTH stimulation test
- low dose dexamethasone suppression test
what two tests can be done to differentiate between pituitary dependent hyperadrenocorticism (PDH) and adrenal dependent hyperadrenocorticism (ADH)?
- ACTH assay
- imaging (abdominal +/- head)
how to perform ACTH stimulation test
5 µg/kg ACTH IV;
cortisol measured at 0 and 1 hours
how to perform low dose dexamethasone suppression test?
0.01 mg/kg dexamethasone IV;
cortisol measured 0, 4, 8 h
name the only licensed product to treat canine hyperadrenocorticism in the UK;
blocks production of glucocorticoids
Trilostane (Vetoryl)
what is the treatment of choice for adrenal dependent hyperadrenocorticism
adrenalectomy
what are the two treatment options for a pituitary mass casing hyperadrenocorticism
- radiation therapy
- hypophysectomy
name the disease
umbrella term for a range of naturally-ocurring or iatrogenic disorders that cause reduced function of the adrenal cortex and results in a state of glucocorticoid deficiency, mineralocorticoid deficience, or both
hypoadrenocorticism
name 4 common routine clinicopathological features of hypoadrenocorticism seen on haematology
- non-regenerative anaemia
- eosinophilia
- lymphocytosis
- lack of stress leukogram
name 5 common routine clinicopathological features of hypoadrenocorticism seen on serum biochemistry
- azotaemia
- hypercalcaemia
- hyperkalaemia
- hyponatraemia
- hypocholesterolaemia
name 2 screening tests for hypoadrenocorticism
- resting cortisol
- UCCR (Urinary cortisol:creatinine ratio)
name 2 treatment options for acute hypoadrenocorticism
- Dexamethasone
- Hydrocortisone CRI
what drug can be used for hormone replacemet of glucocorticoids in chronic hypoadrenocorticism
prednisolone
name the two drug options for replacement of mineralocorticoids in chronic hypoadrenocorticism
- DOCP
- fludrocortisone
name the disease
a syndrome characterised by hyperglycaemia that results from defects in insulin secretion or insulin sensitivity in target tissues OR both
Diabetes mellitus (DM)
what pancreatic islet cell secretes glucagon
(25% of cells)
alpha cells
what pancreatic islet cell secretes insulin
(60% of cells)
beta cells
what pancreatic islet cell secretes somatostatin
(10% of cells)
delta cells
what pancreatic islet cell secretes polypeptide
F cells or PP cells
name 5 clinical signs of Diabetes mellitus (DM)
- PU/PD
- polyphagia
- weight loss
- cataracts/blindness (dogs)
- DKA signs (diabetic ketoacidosis)
what is the concentration of veterinary insulin preparations?
40 IU/mL
what is the concentration of human insulin preparations?
100-300 IU/mL
name 4 common complications of feeding high-fiber diets to dogs
- increased frequency of defecation
- contipation and obstipation
- soft to watery stools
- excessive flatulence
what is the starting insulin dose for cats
0.25 IU/kg
name 3 treatment options for hypersomatotropism in diabetic cats
- increase insulin
- transphenoidal hypophysectomy
- radiotherapy
name the disease
presence of ketones indicative of insufficient insulin;
can be relatively well or feeling ill
ketosis
name the disease
presence of ketones to a large extent overwhelming normal buffering;
patients will be ill and require emergency care
ketoacidosis
what 2 things are important to monitor in an electrolyte panel for a patient with suspected diabetic ketoacidosis
- potassium
- phosphate
(both will be low)
name the 4 most common places of metastases for an insulinoma
- liver
- lymph nodes
- mesentery
- omentum
name 3 differential diagnoses for hypoglycaemia
- insulinoma
- hypoadrenocorticism
- hepatic disease
what is the emergency treatment for an insulinoma?
IV dextrose to effect (not too quickly)
& feed as soon as able
what drug can be given for medical management of an insulinoma to antagonise insulin
prednisolone
name the hormone
released in response to increased blood osmolarity [Na+];
goes to the kidneys and increases water resorption;
constricts arterioles and increases arterial blood presssure
ADH / Vasopressin
what is the treatment for diabetes insipidus
DDAVP
(synthetic vasopressin)
name 4 types of tumours that can arise from the adrenal gland
- glucocorticoid producing
- aldosterone producing
- non-functional
- catecholamine producing
name the type of adrenal tumour
catecholamine producing;
in the medulla
pheochromocytoma
(dogs)
what are the clinical signs caused by with a pheochromocytoma
excessive catecholamine production
name the 3 locations where pheochromocytomas often metastasise to
- lung
- liver
- bone
what is the medical treatment for pheochromocytoma
phenoxybenzamine
(alpha-blocker)
how much body weight should you aim to lose weekly for a cat
1-2% body weight/week
how much of the cardiac output does the kidney recieve?
20%
