Thyroid function and plasma immunoglobulins in subjects with Down's syndrome (DS) during ontogenesis and zinc therapy.

Thyroid function parameters and immunoglobulin concentrations in sera of outpatients with Down's syndrome (DS, n = 110) of different ages (DS1 = 1-9 years; DS2 = 6-15; DS3 = 15-35) were compared with those of age-matched controls (n = 110). Although mean serum TSH was higher in all DS groups, thyroid hormone concentrations were significantly lower only in DS3. In DS1, a notable frequency rate of high T4 and T3 was found. Serum concentrations of thyroxine binding globulin (TBG) were significantly higher in all DS groups. Free T4 and T3 indexes, calculated as the ratio of total hormone: TBG concentrations, were lower in all DS groups. IgA serum concentrations were significantly higher in all DS groups, IgA was higher in DS1 and DS2. Serum zinc levels were lower in all DS groups. Repeated examination after one year revealed lower T4 and higher TSH in DS patients treated with zinc during this interval as compared to values observed before treatment. Our results suggest a high occurrence rate of complex immune and endocrine disorders with thyroid dysregulation in DS patients, with zinc deficiency playing a considerable role.