[Etiological assessment of hyperthyrotropinemia in children with Down's syndrome].

Objective: To study the prevalence of increased TSH level and its probable cause in children with Down's syndrome treated at Policlínica Antônio Cândido.

Methods: The data were collected using medical records of 169 patients. Of these, 46 patients, whose TSH increased at some time during their follow-up, were re-evaluated. In these patients, TSH, free T4, total T4 and thyroid peroxidase autoantibody (anti-TPO) levels were measured. Thyroid ultrasound, iodine-131 scintigraphy, and a perchlorate discharge test were performed.

Results: In 169 children, 86 (50.8%) of whom were male, aged between 1-16 years (median 4 years), 67 (39.6%) presented increased TSH levels. Out of these 67 patients, 46 were prospectively studied. In 31 (67.4%) of them serum TSH returned to normal levels; in 11, TSH remained between 5 and 10 microU/ml, three (6.5%) had a TSH level over 10 microU/ml and one (2.2%) had hyperthyroidism. The diagnoses in 34 patients who were fully studied were: goiter in five (14.7%); Hashimoto's thyroiditis in four (5.9%); hypoplasia in three (8.8%) and iodide organification defect in one (2.9%). The increased TSH levels had a statistically positive relationship with anti-TPO (p = 0.02), but not with gender, abnormal ultrasound or scintigraphy findings. TSH levels did not have any relationship with persistent hyperthyrotropinemia.

Conclusions: In patients with Down's syndrome, slightly elevated and transient TSH levels are frequently detected. Positive anti-TPO antibody test is a key factor in the follow-up of these patients because of its potential risk of progression to manifest thyroid disease.