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What are the different types of endocrine diseases?
- hypothyroidism
- hyperthyroidism
- diabetes mellitus
- hypoadrenocorticism
- hyperadrenocorticism
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What is another name for hypoadrenocoriticism?
Addison's disease
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What is another name for hyperadrenocorticism?
Cushing's disease
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What is another name for diabetes mellitus?
ketoacidosis
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Define endocrinology.
the study of the endocrine glands and their hormones
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What are hormones produced by?
hormones are produced by ductless glands or tissues
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Where are hormones secreted?
directly into the bloodstream
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What do hormones do?
- chemical messengers
- signal target cells to perform different functions
- response to changes in homeostasis
- interact with specific receptors
- these receptors generate a specific biologic response
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How are hormones released throughout the day?
- some hormones are released continuously throughout the day
- some hormones release fluctuates in a rhythm throughout the day
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What do feed-back loops do?
- sense the circulating concentration of a hormone
- suppress or stimulate production
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What are some causes of endocrine disease?
- feed-back loops non-functional
- loss of regulation of hormone production
- gland may work ineffectively or incorrectly
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What are the major endocrine glands?
- thyroid gland
- parathyroid gland
- pineal gland
- pituitary gland
- adrenal gland
- kidney
- ovary
- testis
- pancreas
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What is the most common type of thyroid disease dogs get? Cats?
- dogs: hypothyroidism
- cats: hyperthyroidism
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Where is the thyroid gland located? Can we palpate it?
- ventral cervical region
- lateral margins of the trachea
- usually not palpable in the normal animal
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What types of hormones do the thyroid gland produce?
- T3 - triiodothyronine
- T4 - tetraiodothyronine
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Must have adequate _____ intake to produce thyroid hormones.
iodine
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What processes do the thyroid hormone affect?
metabolic processes
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No tissue or organ escapes the adverse effect of _____.
thyroid excess or insufficiency
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What are the different causes of canine hypothyroidism?
- thyroid atrophy
- lymphocytic thyroiditis
- neoplastic destruction
- iatrogenic
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What happens with thyroid atrophy?
adipose tissue replaces thyroid tissue
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What happens with lymphocytic thyroiditis?
- immune mediated
- antibodies produced against the thyroid
- slow progressive thyroid tissue destruction
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What types of dogs typically get hypothyroidism?
middle-aged dogs
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What are the clinical signs of canine hypothyroidism?
- weight gain with no change in diet
- exercise intolerance
- cold intolerance
- mental dullness
- constipation
- bilateral symmetrical alopecia
- hyperpigmentation
- infertility
- muscle weakness, atrophy
- bradycardia
- concurrent endocrine disease
- lameness
- cranial nerve paralysis (VII facial)
- myopathies
- vestibular disease
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What are the main ways to diagnose canine hypothyroidism?
- mild non-regenerative anemia
- hypercholesterolemia
- mild elevation in ALT and ALKP
- basal T4
- T4 by RIA - radioimmunoassay
- TSH response test
- thyroid antibody concentration
- ELISA
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How do we treat canine hypothyroidism?
thyroid hormone replacement therapy
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What is thyroid hormone replacement therapy?
soloxine
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When will we usually see improvement after treatment for canine hypothyroidism?
- usually in 1 - 3 weeks
- skin and coat improvement takes 4 - 6 weeks
- neurological changes may take months to normalize
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When do we measure the hormone levels after starting treatment for canine hypothyroidism?
4 - 6 weeks after starting treatment
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How often do we monitor a dog after starting treatment for hypothyroidism?
4 - 8 weeks for the next 10 months
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What is feline hyperthyroidism?
excess circulating thyroid hormone
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What is the most common endocrinopathy in cats?
hyperthyroidism
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What is the signalment for feline hyperthyroidism?
- middle aged to older cats
- no gender or sex predilection
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What are the clinical signs for feline hyperthyroidism?
- weight loss
- polyphagia
- vomiting
- PU/PD
- behavior changes - nervous, hyperactive, aggressive, vocalizing
- diarrhea
- heat intolerance
- panting
- tachycardia
- gallop rhythm
- increased blood pressure
- blindness due to retinal detachment
- thin
- murmurs, pleural effusion, CHF
- muscle weakness
- ventroflexion of neck
- unable to jump to high places
- dehydration
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How do we diagnose feline hyperthyroidism?
- palpate enlarged thyroid gland
- mild to moderate elevation in liver enzymes
- increased BUN and creatinine
- radiographs
- basal serum T4 elevated in 95% of hyperthyroid cases
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What do we do if the basal T4 test is normal in a cat we suspect has hyperthyroidism?
repeat in a few weeks because thyroid hormones are known to fluctuate
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What are the different treatments for feline hyperthyroidism?
- surgery
- oral medications
- radioactive iodine 131
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What kind of oral medication do we use to treat feline hyperthyroidism?
Tapazole - methimazole
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When would we use radioactive iodine 131 to treat feline hyperthyroidism and what does it do?
- treatment of choice if no renal failure
- iodine concentrated in thyroid tissue - kills local cells
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What are the advantages to using radioactive iodine 131?
- one injection curative in 95% of cases
- side effects negligible
- not invasive
- destroys intrathoracic thyroid tissue
- can kill malignant cells at high doses
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What are the disadvantages to using radioactive iodine 131?
- hospitalize throughout the time of radioactive clearance (3 - 10 days)
- expensive
- may precipitate onset of renal failure
- transient hypothyroidism
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What do we need to monitor in a cat with hyperthyroidism?
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What is the general term for diseases marked by excessive urination?
diabetes
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What does mellitus mean?
sweet
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What does diabetes mellitus involve?
insulin production or activity
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What does insulin do?
drives glucose into cells for cell usage
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What is diabetes most likely due to in dogs? What is it called?
- lack of insulin production
- insulin dependent diabetes mellitus - type 1
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What types of diabetes do cats get?
- lack of insulin production (insulin dependent diabetes mellitus type 1)
- decreased action by insulin (non-insulin dependent diabetes mellitus type 2)
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What is the average for dogs and cats to get diabetes?
- dogs: average age 7-9 years
- cats: average age 10 years
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Are female dogs or male dogs more at risk for getting diabetes?
female dogs
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What are the clinical signs of diabetes mellitus?
- PU/PD
- weight loss
- polyphagia
- plantigrade stance in cats
- underweight, normal, or obese
- normal to dehydrated
- diabetic cataracts
- ketotic diabetes
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What is plantigrade stance in cats?
cats walking with their hocks on the ground
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What is diabetic cataracts?
- high glucose concentration in lens
- extra glucose converted to sorbitol
- pulls extra water into the lens and breaks down the lens fibers
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How do diabetes become ketotic?
body metabolizes fat for energy, resulting in build up of ketones
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What are the clinical signs of ketotic diabetes?
- depression
- weakness
- tachypnea
- vomiting
- acetone breath
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How do we diagnose diabetes mellitus?
- clinical signs
- fasting blood glucose over 200 mg/dl in the dog (cats blood glucose may be over 200 mg/dl just from stress)
- glucosuria
- ketonuria
- concurrent urinary tract infection
- serum profile
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What do we look for when we are do a serum profile to diagnose diabetes mellitus?
- hyperglycemia
- ALT, ALKP increased
- total bilirubin may be increased
- increased BUN and creatinine
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How do we treat diabetes mellitus?
- insulin therapy: SID or BID
- diet: high in fiber and complex carbohydrates, feed twice daily prior to insulin injection - at consistent intervals
- exercise: consistent amounts and times
- oral hypoglycemics: treat clinically stable, uncomplicated NIDDM
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What do we monitor in an animal with diabetes mellitus?
- watch for lessing of PU/PD
- periodic monitoring of blood glucose concentrations
- if vomiting or anorexia, give 1/2 dose of insulin or not at all
- signs of hypoglycemia
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What are the signs of hypoglycemia and how do we treat it?
- signs: weakness, ataxia, seizures, coma
- treatment: karo syrup rubbed on gums and then go to ER
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Which is more immediately life-threatening, hypoglycemia or hyperglycemia?
hypoglycemia
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Where are the adrenal glands?
- 2 glands
- left and right, dorsal and cranial to each kidney
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What are the two regions of the adrenal gland?
- cortex - outer
- medulla - inner
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What are the hormones produced by the adrenal glands?
- glucocorticoids
- mineralocorticoids
- androgenic (sex) hormones
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What do glucocorticoids do?
- support gluconeogenesis
- suppress inflammation
- suppress immune system
- inhibit cartilage growth and development
- break down proteins and lipids
- help body resist the effects of stress
- important in maintaining homeostasis
- cortisone, cortisol
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What is the principle mineralocorticoid?
aldosterone
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What do mineralocorticoids do?
regulates electrolytes - sodium, potassium, and hydrogen
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Which organ do mineralocorticoids target and what do they do?
- target the kidneys
- resorb sodium
- release potassium and hydrogen
- water comes back into the body with the sodium, affects the water level in the body
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What are the different androgenic hormones?
- male sex hormones
- female sex hormones
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What are the adrenal medulla hormones? What is the release of these hormones controlled by? What does it prepare the body to do?
- epinephrine
- norepinephrine
- release is controlled by the sympathetic nervous system
- prepare body or intense physical activity
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What are the two hormones that regulate the adrenal gland?
- CRH: corticotropin releasing hormone from the hypothalamus which stimulates pituitary to release ACTH
- ACTH: adrenocortioctropic hormone which stimulates the adrenal cortex to release cortisol
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What is another name for hypoadrenocorticism?
Addison's disease
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What is Addison's disease?
- atrophy of the adrenal cortex
- deficiency of secretions of mineralocorticoids and glucocorticoids
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Which species is Addison's disease common in?
not common in dogs, rare in cats
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What is the signalment for Addison's disease?
- middle aged, female
- any breed
- found in families of standard poodles and labradors
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What are the clinical signs of Addison's disease?
- episodic weakness, weight loss
- depression, lethargy
- PU/PD
- GI signs - anorexia, vomiting, diarrhea
- hair loss
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What are the clinical signs of Addisonian crisis?
- weak pulse
- bradycardia
- prolonged CRT
- severe mental depression
- profound muscle weakness
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What lab results do we see with Addison's disease?
- electrolyte abnormalitis - hyponatremia, hypochloremia, hyperkalemia
- increased BUN and creatinine
- acidosis
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How do we diagnose Addison's disease?
- ACTH stimulation test
- endogenous ACTH levels
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What is the ACTH stimulation test?
- animals with Addison's have a low resting cortisol
- the additional ACTH injected should stimulate the production of cortisol in normal animals
- cortisol concentration remains relatively unchanged even with stimulation in animals with Addison's
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How do we treat Addison's disease?
- treat acute crisis with fluid therapy using normal saline, glucocorticoid replacement, desoxycorticosterone pivalate (IM or SQ)
- maintenance therapy
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What are some examples of glucocorticoid replacements?
- dexamethasone
- Solu-Delta-Cortef
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What kind of maintenance therapy do we provide a patient with Addison's disease?
- oral fludrocotrisone (Florinef)
- DOCP - give every 25 - 40 days by injection
- prednisone supplementation
- provide double dose of prenisone at times of stress
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What is DOCP? What does it do?
- desoxycorticosterone pivalate
- acts like aldosterone
- increases sodium retention
- increases potassium excretion
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What is another name for hyperadrenocorticism?
Cushing's disease
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What is Cushing's disease and what causes is?
- hypersecretion of cortisol
- iatrogenic: overmedication with corticosteroids
- adrenal tumor: excess cortisol produced
- pituitary tumor: excess ACTH produced - excess stimulation of adrenal cortex - PDH (pituitary dependant hyperadrenocorticism)
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What is the signalment for Cushing's disease?
- middle aged to older dog
- 60 - 65% females
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What are the clinical signs of Cushing's disease?
- PU/PD
- polyphagia
- heat intolerance, excess panting
- abdominal enlargement - "pot belly"
- muscle weakness, lethargy
- bilateral, symmetrical alopecia, sparing the head and legs
- pruritus, pyoderma
- recurrent urinary tract disease
- insidious onset
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How do we diagnose Cushing's disease?
- Lab tests
- ACTH stimulation test
- low dose dexamethasone suppression test
- ultrasound abdomen - may se adrenal tumor
- MRI - may see pituitary tumor or adrenal enlargement
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What will the lab results show in an animal with Cushings?
- increased ALT, ALKP
- increased cholesterol
- increased blood glucose
- lipemia
- decreased BUN
- UA - UTI, glucosuria, proteinuria,
- minimally concentrated urine
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How do we treat Cushing's disease?
- adrenal tumor: adrenalectomy if unilateral
- radiation of pituitary tumor - expensive, takes 3 weeks, good results
- mitotane (Lysodren) - therapy is the most common treatment
- ketoconazole - inhibits production of certain hormones (steroids, testosterone, cortisol)
- L-deprenyl (selegilline - Anipryl)
- trilostane (Modrenal)
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What does mitotane therapy do?
- causes necrosis of the adrenal cortex
- may affect aldosterone production as well
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How do we do mitotane therapy?
- high initial dose until blood cortisol levels are normal - loading dose
- lower maintenance dose
- can give prednisone during stress
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What kind of client education do we need to provide about Cushing's disease?
- serious disease
- life-long treatment
- periodic monitoring
- overdose with mitotane are common - OD signs like Addison's disease
- prognosis - 20 - 30 months life expectancy
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