Download attitude - Dr. Roberta Dev Anand

ATTITUDE
“THE PEOPLE WHO GET ON IN THIS
WORLD ARE THE PEOPLE WHO GET UP
AND LOOK FOR THE CIRCUMSTANCES
THEY WANT, AND IF THEY CAN’T FIND
THEM, MAKE THEM.”
-GEORGE BERNARD SHAW
ENDOCRINE SYSTEM
DISEASES
R EVIEW
REVIEW OF THE BASICS
Master Endocrine gland: Hypothalamus
Review of the basics
 Endocrine glands- basic units of the
endocrine system.
 Secrete
hormones directly into the bloodstream.
 Ductless glands.
 Exocrine glands- units that secrete their
products onto epithelial surfaces through
tiny tubes called ducts.
REVIEW OF THE BASICS
HORMONES
• Chemical messengers produced by
endocrine glands and secreted directly into
blood vessels.
• Produce effects when bound to their specific
receptors on cells.
–
Each body cell has specific receptors to certain
hormones (target).
HORMONES
Control of Hormone Secretion
• “Negative Feedback System”
– If hormone is of adequate levels, gland will either slow or stop
production of the hormone which is called negative feedback.
• Direct Stimulation of Nervous System
– Secretion of some hormones is stimulated by sympathetic nerve
impulses when an animal feels threatened.
•
Fight or flight response from sympathetic nervous system
DISEASES OF THE THYROID GLAND
HYPERTHYROIDISM
HYPOTHYROIDISM
ANATOMY OF THE TYROID GLAND
Thyroid gland
 Gland not usually palpable
 Located at ventral cervical region along lateral
margins of trachea
 Hormones produced by thyroid gland
 T3 (Triiodothyronine) and T4 (tetraiodothyronine,
thyroxine), iodine containing hormones.


Produced by follicular cells
Calcitonin – Causes calcium deposition in bone which
decreases blood calcium concentrations
 Produced by parafollicular cells
HYPOTHYROIDISM
Hypothyroidism
 MOST COMMON ENDOCRINE DISEASE IN DOGS;
rare in cats

Breeds: Golden Retriever, Doberman, Irish Setter, Schnauzer,
Cocker Spaniel, Dachshund, others
 4-10 yrs of age
 Females
Hypothyroidism
 Definition: clinical state associated with deficiency of
thyroxine, which causes low cell metabolism in most
tissues of the body
 CAUSES:
 Primary acquired – 90% of dogs



Secondary acquired- RARE


Caused by lymphocytic thyroiditis or idiopathic follicular
atrophy
Also by iodine deficiency, neoplasia, infection
Anterior Pituitary dysfunction or destruction from neoplasia – leads
to ↓TSH
Congenital Hypothyroidism-RARE
Hypothyroidism
 Clinical Signs – COMMON FINDINGS
 Weight gain w/o diet change
 Skin changes
Bilaterally symmetric truncal alopecia
 Alopecia of the tail (rat tail), neck, axillae, and
other areas of friction
 Seborrhea
 Superficial pyoderma
 Dry, lusterless haircoat
 Hyperpigmentation
Cold intolerance
Lethargy/sleeping
Exercise intolerance




Hypothyroidism
Hypothyroidism
Hypothyroidism
Hypothyroidism
Hypothyroidism
 Clinical signs/Bloodwork results– Less common
findings

Neuropathies – generalized weakness, ataxia, facial
paralysis/paresis, seizures (secondary to cerebral
atherosclerosis)

GI upset – Constipation, Regurgitation caused by
megaesophagus

Bloodwork abnormalities – hyperlipidemia is most common,
gross lipemia ( milky appearance to the serum),
hypercholesterolemia (80%), anemia (mild non-regenrative)

Eye – hyperlipidemia => corneal lipidosis and anterior uveitis
Hypothyroidism: DIAGNOSIS
 Blood Tests
 Hypothyroid dogs have lowered level of T4

Test total T4(TT4), +/- T3 levels

Free T4: Free T4 is thyroxine that is not
protein bound (ED is most accurate test for
fT4 measurement)

Basal TSH concentration
 Measures TSH in blood, should be used in conjunction with
other tests and clinical signs
*ED = equilibrium dialysis
Hypothyroidism: Considerations
 Remember sick animals and animals on certain
medications (anti-epileptics) may have depressed T4
levels. (Euthyroid sick syndrome)

Wait and re-test after treatment of underlying cause if clinical
signs persist.
 Greyhounds and Scottish deerhounds have low T4
levels naturally; treat if clinically evident.
Hypothyroidism
 Treatment
 Thyroid supplement – L-thyroxine
Oral,
synthetic levothyroxine
Daily administration
 Steady
state levels – 4 wks
 Test levels and adjust dose until T4 normal

Want to test 4-6 hours after dose is given (when serum levels
are highest)
Thyroid replacement hormone
(levothyroxine sodium)
Hypothyroidism
 Client Education
 Supplement
 Daily
dosing (usually BID) required
 Overdose
 Vet
for life
=> hyperthyroidism
may recommend a reduced fat diet
until body weight is satisfactory and T4
levels are normal.
HYPERTHYROIDISM
Hyperthyroidism
Definition: Pathologic, sustained, high overall
metabolism caused by high circulating
concentrations of thyroid hormones
 Most common Endocrine disease in cats (one of
the big 3 diseases of older cats)

Very rare in dogs
 Pathophysiology
 Autonomously hyperfunctioning nodules, no
physiologic controls (functional thyroid adenoma)
 Secrete T4 and T3
Hyperthyroidism in cats
Since 2007, the prevalence of
hyperthyroidism in cats has increased by
19% in mature adult cats, and by 13% in
geriatric cats.
Hyperthyroidism
 Clinical Signs
 Multi-systemic: reflects increase in
metabolism
Weight loss
Polyphagia
Vomiting/diarrhea
Polydipsia/ polyuria
Tachypnea/dyspnea
Hyperactivity
Aggression
Hyperthyroidism
 Clinical signs
 Reflect
increase in metabolism
Tachycardia
+/- heart murmur (thickening
of LV and heart muscle)
Hypertension
Poor body condition
Thickened nails
Unkempt appearance
Large (palpable) thyroid gland 70% bilateral
Hyperthyroid cat
Middle age to older cats
Wt loss
Polyphagia
Tachycardia
Blindness with retinal detachment
Palpable enlarged Thyroid gland
Aggressive
unkempt haircoat
Hyperthyroid cat: Goiter
Hyperthyroidism
 Diagnosis
 Palpate enlarged thyroid gland
 Elevated T4, FT4
 X-rays for associated heart disease
Hyperthyroidism: Scintigraphy
Normal cat
Normal uptake in salivary glands
and thyroid glands
Hyperthyroid cat
Unilateral thyroid adenoma
Hyperthyroidism: Scintigraphy
Hyperthyroid cat
Bilateral thyroid adenoma
Hyperthyroid cat
Ectopic (intrathoracic)
thyroid adenoma
Hyperthyroid cat
Functional thyroid carcinoma
(represents regional metastasis)
Hyperthyroidism
 Treatment
 Methimazole (Tapazole) – anti-thyroid drug –
block incorporation of iodine into thyroglobulin.
COMMON AND PRACTICAL FOR CLIENTS
Radioiodine treatment – I131
 Effective
 Emitted radiation destroys functioning follicular cells
 TREATMENT OF CHOICE
Surgical removal of gland
 May cause hypothyroidism
 May result in hypocalcemia due to hypoparathyroidism



Hyperthyroidism: Medical Rx
METHIMAZOLE
ORAL PILL, BUT CAN BE FORMULATED INTO
A TRANSDERMAL OINTMENT OR FLAVORED TREAT
Hyperthyroidism
 Complications
 Renal disease/failure unveiled when thyroid levels controlled
2-3 months after medication started
Occasionally tapazole will no longer be effective usually after 2-3
years of treatment


 Prognosis
 Excellent if uncomplicated
 If labs show azotemia prior to treatment, prognosis more guarded
Hyperthyroidism: Client Info
 Cause of disease is unknown
 Surgery or Radiation are only cures
 Cat may become hypothyroid following Rx – usually
not clinically significant and supplementation can be
initiated if necessary
 Following Tapazole, Blood pressure and kidney
values should be checked routinely
 Clinical case:
http://veterinarymedicine.dvm360.com/vetmed/Medicine/ImageQuiz-A-dyspneic-cat-with-hyperactivity-andf/ArticleStandard/Article/detail/750137?contextCategoryId=48035