IMPE Abstracts

Introduction: Children with steroid-resistant nephrotic syndrome (SRNS) are at high risk of developing hypothyroidism due to the urinary loss of serum (s) thyroid hormone-binding proteins, thyroxine (T4) and triiodothyronine (T3). There are limited data on the variability in thyroid hormone profiles and replacement doses in pediatric SRNS.

Aims: To analyze the thyroid hormone profile in pediatric patients with SRNS under conservative treatment. To explore a possible relationship between clinical and biochemical data and the dose of levothyroxine required to reach euthyroidism. Materials and methods: Retrospective review of pediatric patients with SRNS and associated hypothyroidism. Hypothyroidism was defined as free sT4 (FT4) below the reference range for age associated or not with an increase in sTSH. Euthyroidism was defined as normalization of FT4 under treatment. Biochemical and clinical data were collected from diagnosis of hypothyroidism to euthyroidism. Proteinuria was calculated in 24 hours urine collection and or proteinuria/creatininuria ratio (P/C ratio).

Results: A total of 21 patients were included. Median age at diagnosis of hypothyroidism was 3.08 years (y), (range, 0.08-11.48; IQR, 1.8-5.16). Median time to euthyroidism was 0.24 y (IQR, 0.12-0.6). 16 of 21 patients were on corticosteroid treatment. Thyroid profile at diagnosis and at euthyroidism is shown in the table. There were no differences in TSH values between patients with and without corticosteroid treatment. At diagnosis FT4 was positively associated with T4 (p 0.002) and T3 (P< 0.001), meanwhile there was no relationship between TSH and T4, FT4 and T3. The median dose of levothyroxine required was 3.1 µg/kg/day (range, 1.2-20.6; IQR, 1.8-1.9). A negative correlation between levothyroxine dose and age was found (p 0.01). Median dose of levothyroxine (µg/kg/day) as a function of age were: 7.6, 4.4 and 2.5 in the groups of patients less than 1 y, 1-4 y and greater than 4 y, respectively. There was a positive association between 24-hour proteinuria and levothyroxine dose (P< 0.05). Median levothyroxine dose (µg/kg/day) were: 5.2, 3.5, 2.1 for proteinuria (mg/kg/day) > 400, 200 - 400 and < 200, respectively. No association was found with P/C ratio.

Conclusion: Serum TSH in this group of SRNS pediatric patients was not related with the severity of hypothyroidism. Higher levothyroxine doses were required at younger age and greater proteinuria.