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
‘CRINE’ – to secrete
Endocrine System Diseases
Main trigger: Hypothalamus
Review of the basics
• Endocrine ____________- basic units of the
endocrine system.
– Secrete hormones ___________ into the
bloodstream.
• Circulate throughout body and produce effects when
attach to receptors in or outside of cells.
– __________ glands.
• Exocrine glands- units that secrete their
products onto epithelial surfaces through tiny
tubes called _____________.
Hormones
• ___________ messengers produced by endocrine
glands and secreted directly into blood vessels.
• Produce effects when find their receptors in or on
cells.
– Each body cell has specific receptors to certain
hormones (___________).
– If body does not have receptor, hormone will pass by.
– Only certain hormones can _______ to receptors and
when it occurs, then it changes the activity of the cell.
Hormones
Control of Hormone Secretion
• “Negative Feedback System”
– Endocrine glands will be stimulated to produce more hormone
when it drops below a certain amount in the body.
– 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
Hypothyroidism
Thyroid Gland
• Gland not usually palpable
• Located at ventral cervical region along lateral margins of
trachea
• Hormones produced
– T3 (___________________) and T4 (_____________________),
iodine containing hormones.
• Produced by follicular cells
– ______________ – Causes Calcium deposition in bone which
decreases blood Calcium concentrations
• Produced by parafollicular cells
Hypothyroidism
• Definition: clinical state associated with
____________________ which causes low cell
metabolism in most tissues of the body
• Primary acquired – 90% of dogs
– Caused by ________________or
_________________________
– Also by iodine deficiency, neoplasia, infection
• Secondary acquired- RARE
– Anterior Pituitary dysfunction or destruction from neoplasia
– leads to ↓TSH
• Congenital Hypothyroidism-RARE
– Cretinism (newborns)
Hypothyroidism
• MOST COMMON ENDOCRINE DISEASE
IN____________; rare in cats
– Breeds: Golden Retriever, Doberman, Irish Setter,
Schnauzer, Cocker Spaniel, Dachshund, others
• 4-10 yrs of age
• Females
• Greyhounds and Scottish deerhounds
physiologically have lower T4 (thyroxine)
Hypothyroidism
• Clinical Signs - COMMON
– __________________________________
– Skin changes
• Bilaterally symmetric truncal alopecia (which
other disease has this clinical sign? )
• ______________________ neck, axillae, and
other areas of friction
• Seborrhea
• Superficial pyoderma
• Dry, lusterless haircoat
• Hyperpigmentation
– Cold intolerance (why?)
– Lethargy/sleeping
– Exercise intolerance
Hypothyroidism
Hypothyroidism
Hypothyroidism
Hypothyroidism
Hypothyroidism
• Clinical signs/Bloodwork – Less common
– ___________________– generalized weakness, ataxia, facial
paralysis/paresis, seizures (secondary to cerebral atherosclerosis)
– _______________– Constipation, Regurgitation caused by
megaesophagus
– Bloodwork abnormalities –_____________lipidemia is most
common, gross lipemia ( milky appearance to the serum),
____________________cholesterolemia (80%), anemia (mild nonregenrative)
– Eye – hyperlipidemia => corneal lipidosis and anterior uveitis
*Virtually all body systems are affected, clinical signs are
generally non-specific
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, glucocorticoids)
may have depressed T4 levels.
(_________________)
– Wait and re-test after treatment of underlying cause
if clinical signs persist.
• Greyhounds have low T4 levels naturally
diagnose based on clinical signs as well as test
results; treat if clinically evident.
Hypothyroidism
• Treatment
– Thyroid supplement – _________________
• Oral, synthetic levothyroxine (0.02 mg/kg BID)
• Daily administration (after cs resolves consider
SID)
– Steady state levels – 4/8 wks (1st 6-8 months)
• 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 for ________________
– Daily dosing required
– Overdose => hyperthyroidism
• Regular rechecks are recommended including
bloodwork.
• PU/PD; nervousness, weight loss, panting, weakness,
inc. appetite
– Vet may recommend a reduced fat diet until body
weight is satisfactory and T4 levels are normal.
Hyperthyroidism
Definition: Pathologic, sustained, high overall
metabolism caused by high circulating
concentrations of thyroid hormones
• Most common Endocrine disease in ____________
(one of the big 3 diseases of older cats)
– Very rare in dogs
• Pathophysiology
– Autonomously ___________________________, no
physiologic controls (functional thyroid adenoma)
– Secrete _______ and ____________
Hyperthyroidism in cats
Hyperthyroidism
• Clinical Signs
– Multi-systemic: reflects increase in metabolism
•
•
•
•
•
•
•
_________________
__________________
Vomiting/diarrhea
_____________________
Tachypnea/dyspnea
Hyperactivity
Aggression
Hyperthyroidism
• Clinical signs cont’d
– ____________________(thickening of LV
and heart muscle)
– Hypertension
– Poor body condition
– Thickened nails
– Unkempt appearance
– ______________________ 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
– ______________________ (Tapazole) – anti-thyroid drug
– block incorporation of iodine into thyroglobulin.
– Monitor: q 2-3 weeks
• COMMON AND PRACTICAL FOR CLIENTS
– Radioiodine treatment – I131
• Effective
• Emitted radiation destroys functioning follicular cells
• ______________________________________________
– Surgical removal of gland
• May cause hypothyroidism
• May result in hypocalcemia due to hypoparathyroidism
Hyperthyroidism: Medical Rx
METHIMAZOLE
ORAL DRUG, BUT CAN BE FORMULATED INTO
A TRANSDERMAL OINTMENT
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 ___________________ 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