Session: MON 471-496-Thyroid Neoplasia & Case Reports
Poster Board MON-496
Methods: Data from 11 patients with MEN 2B and MTC were analyzed (5 M, 6 F, median age 12.8 y (9.1-17.3). Patients had undergone thyroidectomy and received single-drug therapy with VD for >6 months. Confirmed compliance with VD (67 -150 mg/m2/day) and LT was a necessary inclusion criterion. 1 patient was excluded due to LT non-compliance. Data were analyzed using paired t-tests for normally distributed data and the Wilcoxon signed rank test for non-parametric data and are reported as mean (±SD) or median (range).
Results: While on VD treatment, all 11 patients exhibited significantly increased TSH levels. The baseline TSH level was 4.37 mclU/ml (0.08 - 23.30). In comparison, the first peak TSH concentration on VD was 15.70 mclU/ml (12.50 - 137.00, p = 0.0010). The median time it took to reach the first peak of elevated TSH was 1.8 months (0.3 - 9.3). Free T4 levels remained within the normal reference range, yet significantly decreased from baseline levels of 1.47 ng/dL (±0.21) to 1.27 ng/dL (±0.30) when measured at the time of maximum TSH (p = 0.039). TSH levels normalized after subsequent increases in LT doses. An increase from a baseline LT dose of 3.21 mcg/kg/day (±0.77) to 3.99 mcg/kg/day (±0.66) was required in order to resume normative TSH levels (p = 0.0003), equal to an increase of 36.6% (±16.56) in the dosage of LT in mcg/day.
Conclusions: In our cohort of pediatric MTC patients, athyrotic patients with preexisting hypothyroidism developed increased TSH and reduced T4 during the first few months of treatment with VD, necessitating an increase in LT dosage. The 2 patients with normal pretreatment thyroid functions and intact glands showed minimal change in TFTs. Elevated TSH in athyrotic patients may be due to an indirect effect of VD on the metabolism of thyroid hormone, or with thyroid hormone action at the pituitary level. Proper recognition and management of abnormal thyroid hormone levels is critical in growing children on TKIs.
Nothing to Disclose: MBL, EB, NS, EF, MC, LM, AS, PW, AA, FB, BW, CAS
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