Disordini tiroidei nel bambino e nell’adolescente con trisomia 21

Abstract

Thyroid function disorders represent the most frequently detected medical complication among patients with trisomy 21, with a reported prevalence ranging from 4-8% in childhood to 50% or more in adulthood. Over 1% of newborns with Down syndrome show clinical and/or biochemical signs consistent with congenital hypothyroidism, overall, promptly identified by means of the neonatal screening. The 30% of patients are diagnosed with transient congenital hypothyroidism, while 70% show a lifelong need for hormonal replacement therapy with levothyroxine. Afterwards, non-autoimmune subclinical hypothyroidism represents the most frequent finding, with reported prevalence ranging from 23 to 60%. It is still controversial whether subclinical hypothyroidism can be labelled as a pathological condition or represents the expression of a mere asymptomatic upwards shift of TSH, with no clinical impact. In addition, syndrome-related abnormalities in the mechanisms underlying immune tolerance result in a greater occurrence of autoimmune disorders. Graves’ disease and autoimmune hypothyroidism in the setting of Hashimoto thyroiditis are experienced by almost 30% of Down patients. Finally, it is not infrequent that the latter clinical picture switches into hyperthyroidism and vice versa, in an unpredictable clinical continuum. Given the increased lifelong risk of experiencing thyroid function disorders in children and adolescents with Down syndrome, a systematic periodic clinical and biochemical assessment is recommended, in order to promptly detect and eventually treat pathological conditions.