Thyroid function during L-asparaginase therapy in children with acute lymphoblastic leukemia: difference between induction and late intensification.

Parameters of thyroid function were measured in nine children during induction therapy for acute lymphoblastic leukemia (ALL). Seven patients were reevaluated during the late intensification phase. Vincristine, anthracycline drugs (daunorubicin and adriamycin), corticosteroids, and L-asparaginase were used in the two phases of therapy. During induction, L-asparaginase (5,000 U/m2) was given daily on days 1-21. During late intensification, the drug was given on days 1, 4, 8, and 11 (10,000 U/m2). During induction, total T4 significantly decreased from 10.1 +/- 2.3 to 4.0 +/- 1.0 micrograms/dl, FT4 decreased from 1.4 +/- 0.3 to 0.7 +/- 0.2 ng/dl, total T3 decreased from 134 +/- 32 to 57 +/- 21 ng/dl, and thyroxine binding globulin (TBG) decreased from 2.1 +/- 0.6 to 0.8 +/- 0.3 mg/dl. During late intensification therapy, significant decreases in T3 (from 180 +/- 26 to 93 +/- 40 ng/dl) and TBG (from 1.9 +/- 0.5 to 1.1 +/- 0.5 mg/dl) were observed, but there were no significant changes in T4 and FT4. We conclude that during induction, the impairment of thyroid function is attributable to L-asparaginase, whereas during late intensification, low T3 and low TBG is due to glucocorticoid administration.