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Page 6 of 8 Izkhakov et al. J Cancer Metastasis Treat 2021;7:24 https://dx.doi.org/10.20517/2394-4722.2021.24

[5]
of recurrence may be treated by hemithyroidectomy, with laboratory and neck ultrasound follow-up . That
approach allows production of T4 and T3 by the residual thyroid tissue and reduces the negative adverse
[41]
effects of replacement therapy, which depends solely upon LT4 treatment. A study by Ito et al. showed a
positive effect of the maintenance of the postoperative serum T3 level in LT4-treated patients after
hemithyroidectomy compared to those who underwent total thyroidectomy. In a descriptive study of 15
women with newly diagnosed DTC, negative changes in metabolic factors, REE, and body composition
were observed under standard care during the first year following the diagnosis . Those changes paralleled
[39]
decreases in TSH and the TT3/FT4 ratio, implying a higher prevalence of cardiovascular risk factors . In
[39]
healthy adults, exogenous increased TT3 was found to decrease fat and fat-free mass, elevate the energy
[42]
expenditure , and elevate thermogenesis in skeletal muscle by promoting the uncoupling of mitochondrial
energy .
[43]
A decision to perform total thyroidectomy necessarily entails three critical treatment dilemmas: (1) the need
for radioactive iodine treatment; (2) the type of hormone replacement therapy; and (3) the need for TSH
suppression, as well as its extent and duration. The current standard hormone replacement therapy is with
LT4. Based on the results of previous investigations [39,42,43] , we suggest considering the addition of T3 for
cases in which there is a significant decline in the T3/T4 ratio.

Endogenously suppressed TSH was found to be associated with cardiovascular morbidity and mortality in
the general population . The findings of elevated atherosclerotic cardiovascular risk factors as well as
[8,9]
cardiovascular morbidity among TC patients also highlight the importance of a balance between benefits
and detriments when considering exogenous TSH suppression for TC patients [26,27,33] . The extent of TSH
suppression has also been questioned by others . Recently issued research and guidelines advocate such
[44]
treatment only for patients at high risk of DTC recurrence . The clinical implication of these findings is
[5]
that TC survivors are at higher risk for cardiovascular conditions. As such, cardiovascular risk factors need
to be scrupulously monitored among TC survivors.

DECLARATIONS
Authors’ contributions
Conceived and wrote the article: Izkhakov E
Edited the article: Keinan-Boker L
Conceived and edited the article: Stern N

Availability of data and materials
Not applicable.

Financial support and sponsorship
None.

Conflicts of interest
All authors declared that there are no conflicts of interest.

Ethical approval and consent to participate
Not applicable.

Consent for publication
Not applicable.