1. 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

2. ENDOCRINE SYSTEM DISEASES

3. Review of the basics ***
Endocrine glands- basic units of the endocrine system.
These glands secrete hormones directly into the bloodstream.
Ductless

4. Hormones ***
Chemical messengers produced by endocrine glands and secreted directly into blood vessels.
Hormones bind to specific receptors on cells.
Each body cell has specific receptors for certain hormones

5. REVIEW OF THE BASICS
The hypothalamus makes releasing hormones that act on the anterior pituitary gland to make stimulating hormones.
Stimulating hormones travel through the blood stream to target glands, which are stimulated to make their hormones.
Glandular hormones are carried to target tissues where they have their effects.
hypothalamus
Releasing hormones
Anterior pituitary
Stimulating hormones
Glands like thyroid, pancreas,
adrenal
Glandular hormones

6. Hormones

7. Control of Hormone Secretion
“Negative Feedback System”
Hormone production will continue until levels are adequate in the body, then the gland will either slow or stop production of the hormone. This is called negative feedback.

8. DISEASES OF THE THYROID GLAND
HYPOTHYROIDISM
HYPERTHYROIDISM

9. ANATOMY OF THE TYROID GLAND

10. Thyroid gland Hormones produced by thyroid gland
T3 (Tri-iodothyronine)
T4 (tetra-iodothyronine, thyroxine)
Produced by follicular cells of the thyroid gland
Calcitonin – Causes calcium deposition in bone, which decreases blood calcium concentrations
Produced by parafollicular cells in the thyroid gland **we will focus on this hormone later…**

11. HYPOTHYROIDISM

12. Hypothyroidism
Definition: deficiency of thyroxine, which causes low cell metabolism in most tissues of the body
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

13. Hypothyroidism CAUSES: Primary acquired – 90% of dogs
Caused by lymphocytic thyroiditis or idiopathic follicular atrophy
Also by iodine deficiency, neoplasia, infection
Secondary acquired- RARE
Anterior Pituitary dysfunction or destruction from neoplasia – leads to ↓TSH (thyroid stimulating hormone)
Congenital Hypothyroidism-RARE

14. 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

15. Hypothyroidism

16. Hypothyroidism

17. 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
Basal TSH concentration
Measures TSH in blood

18. Hypothyroidism: Considerations
Euthyroid Sick Syndrome: sick animals and animals on certain medications (anti-epileptics) may have depressed T4 levels.

19. Hypothyroidism Treatment Thyroid supplement – L-thyroxine
Oral, synthetic levothyroxine
Daily administration
Steady state levels in the blood takes 4 wks
Test levels and adjust dose until T4 normal
Test 4-6 hours after dose is given (when serum levels are highest)

20. Thyroid replacement hormone (levothyroxine sodium)

21. Hypothyroidism Client Education Supplement for life
Daily dosing (usually BID) required
Overdose => hyperthyroidism
Vet may recommend a reduced fat diet until body weight is satisfactory and T4 levels are normal.

22. “Try to be a rainbow in someone else’s cloud.” -Maya Angelou

23. HYPERTHYROIDISM

24. Hyperthyroidism
Definition: high overall metabolism caused by high circulating concentrations of thyroid hormones
Most common Endocrine disease in cats
Very rare in dogs
Pathophysiology
Autonomously hyperfunctioning nodules, no physiologic controls (functional thyroid adenoma)
Secrete T4 and T3

25. Hyperthyroidism Clinical Signs ***
Multi-systemic: reflects increase in metabolism
Weight loss
Polyphagia
Vomiting/diarrhea
Polydipsia/ polyuria
Tachypnea/dyspnea
Hyperactivity
Aggression

26. Hyperthyroidism Clinical signs *** Tachycardia +/- heart murmur
Reflect increase in metabolism
Tachycardia +/- heart murmur
Hypertension
Poor body condition
Thickened nails
Unkempt appearance
Large (palpable) thyroid gland 70% - bilateral

27. Hyperthyroid cat
Middle age to older cats Blindness with retinal detachment
Wt loss Palpable enlarged Thyroid gland
Polyphagia Aggressive
Tachycardia unkempt haircoat

28. LIVE LIFE!
“Do not fear death so much, but rather the inadequate life.” Bertolt Brecht

29. Hyperthyroid cat: Goiter

30. Hyperthyroidism Diagnosis Palpate enlarged thyroid gland
Elevated T4, FT4
X-rays for associated heart disease

31. Hyperthyroidism: Scintigraphy
Normal cat
Normal uptake in salivary glands
and thyroid glands
Hyperthyroid cat
Unilateral thyroid adenoma

32. Hyperthyroidism: Scintigraphy
Hyperthyroid cat
Bilateral thyroid adenoma
Hyperthyroid cat
Ectopic (intrathoracic)
thyroid adenoma
Hyperthyroid cat
Functional thyroid carcinoma
(represents regional metastasis)

33. Hyperthyroidism Radioiodine treatment – I131 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

34. Hyperthyroidism Treatment Surgical removal of gland
May cause hypothyroidism
May result in hypocalcemia due to hypoparathyroidism

35. Hyperthyroidism: Medical Rx
METHIMAZOLE
ORAL PILL, BUT CAN BE FORMULATED INTO
A TRANSDERMAL OINTMENT OR FLAVORED TREAT

36. Hyperthyroidism Complications Prognosis
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

37. 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

38. DISEASES OF THE PARATHYROID GLANDS
HYPERPARATHYROIDISM
HYPOPARATHYROIDISM

39. Thyroid/Parathyroid glands
1=normal thyroid gland
2 and 3=parathyroid gland
4=enlarged thyroid gland

41. Parathyroid gland Secretion: Parathyroid hormone (PTH, Parathormone)
Function of PTH: To ↑ plasma Ca2+ concentration
1. ↑ osteoclast activity
2. ↑ Ca++ absorption from GI tract
3. ↑ Ca++ reabsorption from kidney tubules
Hyperparathyroidism results in hypercalcemia
Hypoparathyroidism results in hypocalcemia

42. Hyperparathyroidism Causes: Clinical signs: renal and urinary calculi
1º hyperparathyroidism – caused by an adenoma or carcinoma
2º hyperparathyroidism – caused by poor diet, low Ca intake, renal disease
Clinical signs:
Many animals show no clinical signs
signs occur as organ dysfunction occurs
renal and urinary calculi
cardiac arrhythmias, anorexia, vomiting, constipation
weakness

43. Hyperparathyroidism Diagnosis: Routine chemistry panel PTH assay
↑ blood Calcium (normal: ~8-10 mg/dl))
PTH assay
In a normal animal: if blood Ca++ is high, PTH is low (neg feedback)
1º Hyperparathyroidism: Ca++ high, PTH high
Ultrasound – look for enlarged glands or calcium deposits in the urogenital tract

44. Hyperparathyroidism Treatment: Post-Op Care:
Surgical removal of diseased parathyroid
Other options:
Ultrasound-guided chemical (ethanol) ablation
Ultrasound-guided heat (laser) ablation
Post-Op Care:
Hospitalize for 1 wk; ↓PTH may predispose animal to hypocalcemia
Calcium therapy (oral tabs, liquid)
Vit. D supplements (promotes Ca intestinal absorption)

45. Hyperparathyroidism Client Info
Most hyperparathyroid animals show no signs when first diagnosed
Run yearly chem. panels on all normal, older animals

46. Hypocalcemia *** Causes:
Puerperal Tetany (Eclampsia) - late gestation thru post-partum period
Inadequate nutrition
Parathyroid disease
Inadvertent removal of parathyroid during thyroidectomy (most common cause)
Chronic renal failure
Vit. D normally activated in kidney

47. Hypocalcemia Clinical Signs: ***
Restlessness, muscle tremors, tonic-clonic contractions, seizures
Tachycardia with excitement; bradycardia in severe cases (Ca++ is necessary for proper muscle contractions)
Hyperthermia
Stiffness, ataxic

48. Hypocalcemia Diagnosis: Total serum <6.5 mg/dl Treatment:
IV infusion of 10% Ca gluconate solution
Diazepam (IV) to control seizures
Oral supplements of Ca++ (tabs, caps, syrup)
Improve nutrition

49. Hypocalcemia Client info:
Well-balanced diet; increase volume as pregnancy progresses
Signs in pregnant animal is emergency; call vet immediately
May recur with subsequent pregnancies
Early weaning is recommended