Endocrine Abstracts

JOINT2924

Background: Nephropathic cystinosis is a rare genetic disease characterized by defective lysosomal cystine transport due to mutation in CTNS gene and consequently increased lysosomal cystine. Hypothyrodism is a known complication of nephropathic cystinosis but the pathogenesis of thyroid dysfunction appears to be more complex than merely thyroid gland destruction by lysosomal cysteine.

Methodology: Prospectively fifteen patients with infantile nephropathic cystinosis had been recruited from Cystinosis Clinic, Children’s Hospital, Cairo University. Laboratory assessment of thyroid profile included free T4, free T3, TSH, thyroid autoantibodies (anti-thyroglobulin antibodies, anti-peroxidase antibodies) were measured. Thyroid ultrasound was done to all patients by a single operator.

Results: The age of recruited patients ranged from 5 to 10 years with mean age of 7.87+ 1.7 years. The frequency of hypothyroidism among our cohort was 8 patients (53.3%). Most of the affected patients were males 75% with their mean age was 8.25+1.17 years old. However, the age of diagnosis of thyroid dysfunction ranged from 1 to 8 years old with mean age of 4.87+ 2.08 years. All patients (100%) had negative anti- peroxidase antibodies (TPO). As regards anti thyroglobulin antibodies (TG), 2 patients among euthyroid group had positive titer and only 1 patient among hypothyroid group had borderline titer. All patients with hypothyroidism were on thyroid hormone replacement therapy in the form of Levothyroxine. The dose of replacement therapy ranged from 50 to 150 (µg/day) with mean dose of 71.8 +34.08(µg/day). Only 5 patients were compliant to treatment and well controlled but the remaining 3 patients were not controlled. Thyroid ultrasound revealed very small thyroid gland for age among both euthyroid and hypothyroid group.

Conclusion: Hypothyroidism is a frequently reported complication among our cohort of patients with nephropathic cystinosis. There is no role of autoantibodies (anti-thyroglobulin, anti-peroxidase) in the pathogenesis of thyroid gland destruction. Patients with nephropathic cystinosis have small volume thyroid gland regardless of their thyroid status.