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
