Dose-dependent relationship between levothyroxine and health-related quality of life in survivors of differentiated thyroid cancer.

Among survivors of differentiated thyroid cancer, 67.5% were prescribed levothyroxine for thyroid hormone replacement therapy.

• Study sample included 782 patients with differentiated thyroid cancer from the linked 2007-2017 SEER-Medicare Health Outcomes Survey.
• Mean defined daily dose was 123 μg with a standard deviation of 44.1 μg.
• Data were obtained from Medicare Advantage enrollees, representing an older population.
• Differentiated thyroid cancer included papillary, follicular, and Hürthle cell subtypes.

Greater levothyroxine defined daily dose was associated with greater relative risk of low health-related quality of life on the Role Limitation measure.

• Relative risk of low (compared with moderately low) HRQoL for Role Limitation was 4.9 (95% CI, 2.1–11.6).
• Defined daily dose was classified as low, average, or high based on standard deviations around body mass index-specific means.
• Association was tested using multinomial logistic regression.
• HRQoL was measured using the Veterans RAND 12-item Quality of Life Survey (VR-12), categorized by T score.

Greater levothyroxine defined daily dose was associated with greater relative risk of low health-related quality of life on the Social Functioning measure.

• Relative risk of low (compared with moderately low) HRQoL for Social Functioning was 5.6 (95% CI, 2.5–12.5).
• Low HRQoL was defined as T scores ≤25, moderately low as 25 < T scores ≤50, and high as T scores >50.
• High defined daily dose was also associated with greater relative risk of multiple low-scoring HRQoL measures beyond Social Functioning and Role Limitation.

Long-term survival for differentiated thyroid cancer exceeds 95%, yet self-reported health-related quality of life scores remain low compared with survivors of cancers with worse prognoses.

• This discrepancy between survival outcomes and patient-reported HRQoL motivated the study hypothesis.
• Prior reports suggest thyroid hormone replacement therapy is associated with lower HRQoL.
• The study used a cross-sectional design to test the association between levothyroxine dose and HRQoL.

Greater-than-average thyroid hormone replacement therapy dosages were associated with lower health-related quality of life across multiple domains among differentiated thyroid cancer survivors.

• Associations were found on several VR-12 measures including Role Limitation and Social Functioning.
• Results held after multinomial logistic regression controlling for BMI-specific dosing means.
• The authors conclude that thyroid hormone replacement therapy dose adjustment warrants close attention to address functional and psychosocial well-being.
• The study population was limited to Medicare Advantage enrollees (2007–2017), which may limit generalizability to younger patients.