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OBJECTIVE: The incidence of cranial radiotherapy (cRT)-induced central hypothyroidism (TSHD) in childhood brain tumor survivors (CBTS) is reported to be low. However, TSHD may be more frequent than currently suspected, as its diagnosis is challenging due to broad reference ranges for free thyroxine (FT4) concentrations. TSHD is more likely to be present when FT4 levels progressively decline over time. Therefore, we determined the incidence and latency time of TSHD and changes of FT4 levels over time in irradiated CBTS. DESIGN: Nationwide, 10-year retrospective study of irradiated CBTS. METHODS: TSHD was defined as 'diagnosed' when FT4 concentrations were below the reference range with low, normal or mildly elevated thyrotropin levels, and as 'presumed' when FT4 declined ≥ 20% within the reference range. Longitudinal FT4 concentrations over time were determined in growth hormone deficient (GHD) CBTS with and without diagnosed TSHD from cRT to last follow-up (paired t-test). RESULTS: Of 207 included CBTS, the 5-year cumulative incidence of diagnosed TSHD was 20.3%, which occurred in 50% (25/50) of CBTS with GHD by 3.4 years (range, 0.9-9.7) after cRT. Presumed TSHD was present in 20 additional CBTS. The median FT4 decline in GH-deficient CBTS was 41.3% (P < 0.01) to diagnosis of TSHD and 12.4% (P = 0.02) in GH-deficient CBTS without diagnosed TSHD. CONCLUSIONS: FT4 concentrations in CBTS significantly decline over time after cRT, also in those not diagnosed with TSHD, suggesting that TSHD occurs more frequently and earlier than currently reported. The clinical relevance of cRT-induced FT4 decline over time should be investigated in future studies.
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Purpose To evaluate the prevalence of, and risk factors for, early endocrine disorders in childhood brain tumor survivors (CBTS). Patients and Methods This nationwide study cohort consisted of 718 CBTS who were diagnosed between 2002 and 2012, and who survived ≥ 2 years after diagnosis. Patients with craniopharyngeoma or a pituitary gland tumor were excluded. Results of all endocrine investigations, which were performed at diagnosis and during follow-up, were collected from patient charts. Multivariable logistic regression was used to study associations between demographic and tumor- and treatment-related variables and the prevalence of early endocrine disorders. Results After a median follow-up of 6.6 years, 178 CBTS (24.8%) were diagnosed with an endocrine disorder. A total of 159 CBTS (22.1%) presented with at least one endocrine disorder within the first 5 years after diagnosis. The most common endocrine disorders were growth hormone deficiency (12.5%), precocious puberty (12.2%), thyroid-stimulating hormone deficiency (9.2%), and thyroidal hypothyroidism (5.8%). The risk of hypothalamic-pituitary dysfunction (n = 138) was associated with radiotherapy (odds ratio [OR], 15.74; 95% CI, 8.72 to 28.42), younger age at diagnosis (OR, 1.09; 95% CI, 1.04 to 1.14), advanced follow-up time (OR, 1.10; 95% CI, 1.02 to 1.18), hydrocephalus at diagnosis (OR, 1.77; 95% CI, 1.09 to 2.88), and suprasellar (OR, 34.18; 95% CI, 14.74 to 79.29) and infratentorial (OR, 2.65; 95% CI, 1.48 to 4.74) tumor site. Conclusion The prevalence of early endocrine disorders among CBTS is high. The observation that 22.1% of CBTS developed at least one endocrine disorder within the first 5 years after diagnosis stresses the importance of early and regular assessment of endocrine function in CBTS who are at risk for endocrine damage.
