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How I manage endocrine cases (Proceedings)

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Oct 01, 2008

Thyroid Function

  • ↑ mitochondrial number and size
  • ↑activity of Na,K-ATPase
  • 15% to 40% of your Basal Energy
  • Increased energy expenditure of the cell
  • ↑protein synthesis and catabolism
  • ↑ heat production
  • Stimulate basal metabolic rate

Thyroid Function in the Fetus/Neonate

  • ↑ mental activity and neural development
  • ↑ lung maturation
  • ↑ gastrointestinal function
  • ↑ cardiovascular function
  • ↑ growth and maturation of the skeletal system

Hypothyroidism

Primary

Secondary / Tertiary

  • Problem with conversion of T4 to T3 in peripheral tissues
  • TSH
  • TRH

"False" (Non-thyroidal Illness)

Hyperthyroidism

Factors Affecting Thyroid Levels

Physiologic/pathologic influences

  • NSAID administration
  • Decrease levels for 2 weeks!
  • Corticosteroid administration
  • High energy or protein diets
  • > 30% of Diet Concentrate levels will decrease
  • > 50% then levels decrease to very low levels
  • High zinc or copper diets
  • Food deprivation
  • High intensity exercise
  • Non-thyroidal illness syndrome

What DVM's associate with low thyroid levels

  • Anhidrosis
  • Alopecia
  • Chronic Laminitis
  • Infertility
  • Obesity
  • Orthopedic disease
  • Congenital hypothyroidism/dysmaturity syndrome

Thyroidectomized horses

  • Retarded growth
  • Increased sensitivity to cold
  • Edema of lower legs
  • Decreased feed consumption
  • Weight loss
  • Decreased Cardiac Output
  • Increased blood/plasma volume

Non Thyroidal Illness

  • Low thyroid levels to help decrease metabolic rate
  • Conservation of lean mass
  • Decreased conversion of T4→T3

DIAGNOSTICS

  • Rule out other diseases
  • Sick euthyroid
  • Free T4/T3 and Total T4/T3
  • Free T4 either by Dialysis or Diasorin two
  • IF fT4 and fT3 are normal→ Not hypothyroid
  • Even IF Total T4 and T3 are low
  • If fT4 and fT3 are low then:
  • Repeat test / Rule Out Sick euthyroid
  • Perform TRH stimulation test
  • TRH Stimulation Test
  • No sterile medical preparation available
  • 1mg IV Horse
  • 0.5 mg IV Pony
  • Pre-Sample
  • Post Sample 2 hours Post
  • Look for peak in T3
  • Response to Treatment