Optimal Levothyroxine Dosing Strategy for Immune Checkpoint Inhibitor-related Hypothyroidism: A Retrospective Study.

Patients with transient thyrotoxicosis followed by overt hypothyroidism required higher LT4 doses than those with isolated overt hypothyroidism.

• The mean difference in LT4 dose between the two hypothyroidism patterns was 0.23 µg/kg/day (95% CI, 0.08–0.38).
• The study included a total of 109 patients with ICI-related hypothyroidism at a tertiary academic hospital.
• This was a retrospective study design.

A rapid titration strategy significantly improved the cumulative incidence of achieving normal free thyroxine levels compared to conventional titration.

• The hazard ratio for achieving normal free thyroxine levels with rapid vs. conventional titration was 4.44 (95% CI, 2.24–8.82).
• The rapid titration strategy was applied to patients with ICI-related overt hypothyroidism and no cardiac disease who had elevated TSH levels within 4 weeks of the last documented low or normal TSH.
• The safety profile of rapid titration was described as comparable to conventional titration.

A rapid titration strategy significantly improved the cumulative incidence of achieving normal TSH levels compared to conventional titration.

• The hazard ratio for achieving normal TSH levels with rapid vs. conventional titration was 4.11 (95% CI, 2.18–7.73).
• The rapid titration strategy was implemented specifically in patients without cardiac disease whose TSH elevation was detected within 4 weeks of a previously low or normal TSH.
• No significant increase in adverse effects was observed with the rapid titration approach.

A predictive equation for optimal LT4 dose at euthyroid state was developed for patients with thyrotoxicosis followed by overt hypothyroidism.

• The equation is: Predicted LT4 dose (µg/kg/day) = (−0.016 × body weight) + (0.109 × baseline TSH level) + 2.661.
• This equation applies specifically to the subgroup with transient thyrotoxicosis followed by overt hypothyroidism.
• Body weight and baseline TSH level were the two variables incorporated into the predictive model.

ICI-related hypothyroidism is mostly irreversible, making prompt thyroid hormone replacement therapy crucial, particularly for patients undergoing neoadjuvant immunotherapy.

• The study was motivated by the clinical need for an optimized titration strategy given the irreversible nature of most ICI-related hypothyroidism.
• The study population consisted of 109 patients treated at a tertiary academic hospital.
• The study compared rapid versus conventional titration strategies as the primary intervention.