Thyroid Disorder

Overview

Thyroid function in the neonatal period

An estimated 1% of babies with Down syndrome have a raised TSH on newborn screening, but classical congenital hypothyroidism due to thyroid dysgenesis is not common.
Raised TSH should prompt further investigation, and consideration of treatment with thyroxine.
Borderline thyroid dysfunction in the neonate may be transient, and when treatment is started in these cases , treatment should be stopped after the age of 2 years and thyroid function reassessed off treatment.
At present there is no hard evidence to justify routinely treating infants with Down syndrome with thyroxine, if they have normal thyroid function.

Thyroid function beyond the neonatal period

Thyroid dysfunction , mainly hypothyroidism occurs more commonly in people with Down syndrome at all ages, when compared with the general population.
The prevalence of autoimmune thyroiditis increases with age in Down syndrome.
Clinical diagnosis of hypothyroidism may be unreliable in Down syndrome because of overlap with features commonly seen in the syndrome e.g. dry skin, thin hair and constipation.
Screening for thyroid dysfunction is required throughout life.
Capillary TSH testing is a practical reliable method. This can be done by fingerprick samples and on the same cards as used for newborn screening.
Mild elevation of TSH with normal fT4 and no symptoms may not require treatment.
Hyperthyroidism is less common than hypothyroidism, but occurs more frequently than in the general population.