Baseline TSH within reference range and incident thyroid dysfunction in cancer patients: a retrospective cohort study

Area of Science:

• Endocrinology
• Oncology
• Clinical Medicine

Background:

• Thyroid dysfunction is a common complication in cancer patients.
• The predictive value of baseline thyrotropin (TSH) within the reference range for thyroid dysfunction in cancer patients is not well understood.
• Normal baseline thyroid function is often assumed, but subclinical variations may impact outcomes.

Purpose of the Study:

• To investigate the association between baseline TSH levels within the reference range and the development of thyroid dysfunction in hospitalized cancer patients.
• To determine if TSH levels, even within the normal range, can stratify risk for incident thyroid dysfunction.
• To explore the relationship between baseline TSH and clinical thyroid dysfunction or mortality.

Main Methods:

• Retrospective cohort study of 532 hospitalized cancer patients with normal baseline thyroid function.
• Baseline TSH levels were modeled using restricted cubic splines and categorized as low (<1.02 mIU/L), optimal (1.02-2.00 mIU/L), or high (>2.00 mIU/L).
• Primary outcome was overall thyroid dysfunction; secondary outcomes included clinical dysfunction and mortality, analyzed using multivariable Cox models and restricted mean survival time (RMST).

Main Results:

• Overall thyroid dysfunction occurred in 32.9% of patients.
• A U-shaped association was observed between baseline TSH and overall thyroid dysfunction (P < 0.001), with the lowest risk in the optimal TSH range (1.02-2.00 mIU/L).
• Both low TSH (HR 1.90) and high TSH (HR 2.22) independently predicted increased risk compared to optimal TSH. High TSH also predicted clinical dysfunction (HR 1.71), but no association with mortality was found.

Conclusions:

• Baseline TSH levels within the reference range exhibit a U-shaped association with incident thyroid dysfunction in hospitalized cancer patients.
• The optimal TSH range for lowest risk of thyroid dysfunction was identified as 1.02-2.00 mIU/L.
• Risk stratification using baseline TSH within the conventional reference range may enable personalized monitoring strategies for cancer patients undergoing treatment.