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Equine Thyroid Disease - Coggle Diagram
Equine Thyroid Disease
goiter
thyroid enlargement
may or may not be associated with thyroid dysfunction
causes
benign thyroid adenoma in older horses
common
thyroid fxn usually normal
thyroid cysts
normal fxn
thyroid neoplasia
iodine deficiency or excess
testing
limited TRH and TSH testing
cost and availability problem
requires multiple samples over time
TRH stimulation test FYI
collect baseline blood sample, then give 1mg TRH IV
TRH stimulation yields a 2.5 -3x rise in TSH at 1 hr post-admin
T3 (free and total) peak by 2hrs and should increase to at least 2x baseline concentrations
T4 (free and total) peak at 4-6 hrs. Total T4 should be at least 2x baseline and free T4 should increase to at least 1.7x baseline
total
T3, T4, and free T4
hyperthyroidism
IR/metabolic syndrome
induced mild
facilitated by weight loss and imporved insulin sensitivity
adjunct to dietary control and implemntation of an exercise programs
48mg/day/horse PO
goal is
short-term use
(months) until the target BCS is reached
treatment
levothyroxine
greater weight loss
increased insulin sensitivity
lack of significant adverse effects
short-term management of EMS is the most common application for this drug
rare
all documented cases are assocaited with thyroid neoplasia
CS
weight loss
tachycardia
tachypnea
hyperactivity
ravenous appetite
diagnosis
elevated total and free fractions of thryoid hormone
treatment
partial or complete thyroidectomy
hypothyroidism
experimental
CS
obesity
low body temp and HR
poor atheltic performance
poor haircoat
mm weakess
low-grade anemia
abnormal estrus cycles
poor libido
face and limb edema
hyperpigmentation
fetal/congenital
CS
abortion
developmental immatuirity
incomplete tarsal/carpal ossificaiton
mandibular prognathism
flexural deformities
rupture of common digital extensor tendon
poorly developed pectoral mm
+/- goiter
treatment
correct mare nutrition
thyroid hormone supplementation if testing supports inadequate function
supportive care
treat
FPT
infections
limb problems
avoid collapse of tarsal/carpal bones while ossification occurs
stall rest
splinting
developmental and musculoskeletal abnormalities in affected neonatal foals
primary nutritional disorder
dam's diet contains insufficient/excessive iodine or [nitrates]
impaired fetal thyroid function
abnormal growth and development in utero
poor prognosis
primary
very rare
overdiagnosed
low [TH] is more likely to be...
side effect of medications
nonthyroidal illness syndrome
transient reversible hypothyroid state
stress
illness
systemic inflammation
HPT axis suppression at hypothalamus or pituaitary
physiological significance of NTIS is unclear
no evidence of adverse effects
no clear indication of exogenous TH
misdiagnosis may lead to thyroxine misues
over-supplemtnation associated with...
osteoporosis
atrial fibrillation
myocardial infarction
CHF
treatment
titrate dose to maintain hormone levels within normal reange
neonatal congenital hypothyroidism due to iodine deficiency rarely respond to exogenous thyroxine