[The prevalence of thyro-peroxidase antibodies and thyroid function in Turner's syndrome].

BACKGROUND

Higher frequency of autoimmune diseases in patients with Turner's syndrome (TS) compared with the general population has been described. 5 to 10% of cases occur before adolescence. The goal of the study was to determine the prevalence of thyro-peroxidase antibodies (TPO-Ab) in correlation with karyotype, clinical symptoms and hormonal thyroid function in TS patients.

METHODS

96 girls with TS, aged 0.5-19.8 years (mean age 12.3+/-5.0) and 58 girls matched for age and BMI (control group) were analysed. The diagnosis of TS was established basing on clinical features and karyotype analysis. 54 had X monosomy, 7--isochromosome, 1--other X chromosome aberration, 11--mosaicism 45,X/46,XX, 3--45,X/47,XXX, 1--45,X/46,XX/47,XXX, 19--mosaicism with structural aberration: 12--45,X/46,X,i(Xq), 2--others, 5--with Y chromosome. In all children TSH, FT(4), FT(3), TPO-Ab, cholesterol, triglyceride levels, physical and ultrasonographic examination were performed.

RESULTS

25% of TS patients were positive for TPO-Ab. This frequency was significantly higher (p=0.0017) than that seen in the control group (5.2%). Positive titers of TPO-Ab were found: in 42% of girls with isochromosome (46,X,i(Xq) and 45,X/46,X,i(Xq)), 22.2% with X monosomy, and 17.4% with other karyotypes. The percentage of positive TPO-Ab titres increased with cumulative age of TS patients. It was 6.7% at the age of 10 years and almost doubled (12.1%) one year later. The next strong increase was observed at the age of 16 (up to 19.1%) and gradually rose to 20 years of age. Mean age of seronegative patients was significantly lower than that of seropositive patients (p=0.018). Only 2 patients manifested symptoms of hyperthyroidism requiring short period of antithyroid treatment. Others did not reveal any clinical features of thyroid dysfunction, although developed thyroid abnormalities such as elevated TSH (11.4%) or goiter (28%). Lack of correlation between TPO-Ab, thyroid hormones and lipid levels was associated with L-thyroxine supplementation, in patients with mildly elevated TSH, prior to the study.

CONCLUSIONS

Patients with TS, especially with isochromosome, have antithyroid antibodies more frequently than their co-evals. Therefore, it is important to monitor TPO-Ab from about the age of 10 years even in asymptomatic patients. However, in routine clinical practice, both the thyroid examination and TSH level (even in asymptomatic patients) should be screened yearly for early detection of subclinical hypothyroidism and risk of more severe growth retardation in girls with TS.