Page 2746 - Cote clinical veterinary advisor dogs and cats 4th

1429.e2 Hypothyroidism: Treatment

Hypothyroidism: Treatment
VetBooks.ir Use brand name levothyroxine

for animal use (initial dose should
be 0.02 mg/kg of body weight
orally q 12h with the
maximum initial dose of 0.8 mg
orally q 12h)

Evaluate clinical response
along with 4- to 6-h
postpill serum TT4 and
TSH serum concentrations after
4 to 8 weeks of treatment*
Positive Inadequate or absent
clinical response clinical response

Postpill serum Postpill serum
concentrations concentrations

T4 low normal 40% above 40% above High normal to slightly
TSH high high normal high normal higher than normal

Decrease dosage or
Increase dosage consider once-daily
therapy † Re-evaluate diagnosis T4 low normal
including measurement TSH high
of TgAA
Recheck in Recheck in
4 weeks 4 weeks
Recheck in 8 weeks Increase dosage
High normal to slightly
higher than normal
Positive Inadequate or absent
clinical response clinical response
No change
necessary
Consider:
1. Increasing dosage
Recheck in 2. Treatment q 8h
6 months 3. Misdiagnosis

*Serum free T4 by equilibrium dialysis can also be measured.
† Prepill serum T4 also recommended if once-daily therapy is administered.
T4, Thyroxine; TgAA, serum thyroglobulin autoantibodies; TT4, total serum thyroxine concentration; TSH, thyroid-stimulating hormone.

(Modified from Ettinger SJ, Feldman EC: Textbook of veterinary internal medicine, ed 7, St. Louis, 2010, Elsevier.)

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