Objective—To determine efficacy and safety of percutaneous
radiofrequency heat ablation for treatment
of hyperthyroidism in cats.
Procedure—Hyperthyroidism was diagnosed via clinical
signs and high serum total (TT4) and free thyroxine
(fT4) concentrations. One or 2 hyperfunctional cervical
thyroid nodules were detected by use of scintigraphy
and ultrasonography. If cats had 1 abnormal thyroid
lobe, heat ablation was performed on that lobe; if
cats had 2 abnormal lobes, heat ablation was applied
to the larger lobe. Overall, heat ablation was performed
14 times in the 9 cats. Clinical signs and
serum TT4, fT4, and calcium concentrations were
monitored daily for 2 days after the procedure, weekly
for the first month, and then monthly. Laryngeal
function was evaluated and cervical ultrasonography
and thyroid scintigraphy were also performed.
Monitoring continued for as long as 9 months after
heat ablation if a cat became euthyroid or until an
owner chose an alternative treatment because of
recurrence of hyperthyroidism.
Results—Serum TT4 and fT4 concentrations transiently
decreased after all 14 heat ablation procedures (≤
reference range after 10 of 14 treatments) within 2
days after the procedure. Cats were euthyroid for 0 to
18 months (mean, 4 months). Hyperthyroidism
recurred in all cats. Adverse effects included transient
Horner's syndrome (2 cats) and laryngeal paralysis
without clinical signs (1 cat).
Conclusions and Clinical Relevance—Percutaneous
heat ablation as a treatment for hyperthyroidism in cats
is effective transiently but not permanently. (J Am Vet
Med Assoc 2003;223:1602–1607)