Download Thyroid replacement hormone (levothyroxine sodium)

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