Thyroid function and thyroid autoimmunity in childhood acute lymphoblastic leukemia off-therapy patients treated only with chemotherapy

Objective: Scanty data are available about the thyroid function in childhood acute lymphoblastic leukemia (ALL) off-therapy patients treated only with chemotherapy. We aimed to assess the prevalence of thyroid autoimmunity and thyroid dysfunction in such patients. Design: Case-control cross-sectional study. Methods: Eighty-four patients diagnosed with ALL and treated only with chemotherapy. Mean age at diagnosis 5.9±3.6 yr, at recruitment 12.1±4.3 yr. The treatment had been stopped 4.3±3.2 yr before recruitment. A control group of 60 subjects was recruited. Free T₄, TSH, anti-thyroperoxidase, and anti-thyroglobulin antibodies were measured. Results: Anti-thyroglobulin and anti-thyroperoxidase antibodies were negative in all patients. TSH was increased in 7 patients (8.3%) and 3 controls (5.0%). Free T₄ was within the normal limits in all patients and controls. Mean TSH and free T₄ levels did not statistically differ between controls and ALL off-therapy patients. TSH was negatively correlated with the age at the diagnosis (p=0.01) and the age at the end of therapy (p=0.008). Anti-thyroglobulin and/or anti-thyroperoxidase antibodies were detected in 3 controls (5%; vs study group: p=0.038), 1 of them with increased TSH. Conclusions: Some patients present hyperthyrotropinemia, without anti-thyroid antibodies, with a prevalence comparable to the control group. The thyroid gland seems more prone to be damaged by chemotherapy at a younger age. We think that a thyroid follow-up in ALL off-therapy patients may be advisable and should be differentiated on the basis of the age at the end of treatment, with more frequent tests for younger patients.