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 non-regenrative)

– Eye – hyperlipidemia => corneal lipidosis and anterior uveitis

*Virtually all body systems are affected, clinical signs aregenerally 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 Blindness with retinal detachmentWt loss Palpable enlarged Thyroid glandPolyphagia AggressiveTachycardia unkempt haircoat

Hyperthyroid cat: Goiter

Hyperthyroidism

• Diagnosis– Palpate enlarged thyroid gland

– Elevated T4, FT4

– X-rays for associated heart disease

Hyperthyroidism: Scintigraphy

Normal catNormal uptake in salivary glandsand thyroid glands

Hyperthyroid catUnilateral thyroid adenoma

Hyperthyroidism: Scintigraphy

Hyperthyroid catBilateral thyroid adenoma

Hyperthyroid catEctopic (intrathoracic)thyroid adenoma

Hyperthyroid catFunctional 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