Download EndocrineDiseases pt1 2016

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
Review of the basics ***
Endocrine glands- basic units of the endocrine
system.
 These glands secrete hormones directly into the
bloodstream.
 Ductless
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
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
Hormones
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.
DISEASES OF THE THYROID GLAND
HYPOTHYROIDISM
HYPERTHYROIDISM
ANATOMY OF THE TYROID
GLAND
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…**
HYPOTHYROIDISM
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
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
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: 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
Hypothyroidism: Considerations
Euthyroid Sick Syndrome: sick animals and animals on certain
medications (anti-epileptics) may have depressed T4 levels.
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)
Thyroid replacement hormone (levothyroxine sodium)
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.
“Try to be a rainbow in
someone else’s cloud.”
-Maya Angelou
HYPERTHYROIDISM
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
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
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
LIVE LIFE!
“Do not fear death so much, but rather
the inadequate life.”
- Bertolt Brecht
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
Hyperthyroidism
Treatment
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
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
DISEASES OF THE PARATHYROID GLANDS
HYPERPARATHYROIDISM
HYPOPARATHYROIDISM
Thyroid/Parathyroid glands
1=normal thyroid gland
2 and 3=parathyroid gland
4=enlarged thyroid gland
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
Hyperparathyroidism
 Causes:
 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
Hyperparathyroidism
Diagnosis:
 Routine chemistry panel
 ↑ 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
Hyperparathyroidism
 Treatment:
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)
Hyperparathyroidism
Client Info
Most hyperparathyroid animals show no signs when first
diagnosed
Run yearly chem. panels on all normal, older animals
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
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
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
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