van Iersel L, Xu J, Potter BS, Conklin HM, Zhang H, Chemaitilly W, van Santen HM, Merchant TE. Clinical Importance of Free Thyroxine Concentration Decline After Radiotherapy for Pediatric and Adolescent Brain Tumors.
J Clin Endocrinol Metab 2019;
104:4998-5007. [PMID:
31173083 DOI:
10.1210/jc.2019-00539]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 06/03/2019] [Indexed: 11/19/2022]
Abstract
CONTEXT
Clinical significance of a decline in free T4 (FT4) concentrations across the reference range in children with brain tumors treated with radiation therapy (RT) is uncertain.
OBJECTIVES
To study trends in FT4 in children after RT and risk factors and health outcomes associated with plasma FT4 concentrations.
DESIGN AND SETTING
Longitudinal, single-center retrospective cohort study.
PATIENTS
Low-grade glioma or ependymoma patients (n = 267; age ≤25 years) who received RT (50.4 to 59.4 Gy) at a single institution (1996 to 2016) and followed with serial FT4 measurements.
MAIN OUTCOME MEASURE
A linear mixed-effects model with a random intercept was used to investigate risk factors for longitudinal changes in FT4 concentrations. A two-stage mixed-effects model examined associations between clinical outcomes and plasma FT4 concentrations.
RESULTS
FT4 concentrations declined over time after RT (P < 0.001). Females (P < 0.001) and younger patients (P < 0.001) demonstrated greater declines in FT4 concentrations over time. The rate of weight gain, but not of height loss, increased with a higher FT4 decline rate (P < 0.001). At last follow-up, patients with lower baseline FT4 concentrations had increased risk of glucose disorder (OR, 19.73; P = 0.002) or dyslipidemia (OR, 19.40; P = 0.003) but not high fat mass (P = 0.18). Lower baseline FT4 concentrations were not associated with impaired scores for intelligence, attention, memory, or psychosocial functioning.
CONCLUSIONS
FT4 concentrations significantly decline in children with brain tumor after RT. Variation and trends in FT4 concentration are associated with physical health outcomes. Future studies should assess whether continuous FT4 concentrations and trends, rather than population-based cut-off values, can distinguish between euthyroid and hypothyroid states.
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