Objectives To assess uptake of community-based capillary thyroid stimulating hormone (TSH) screening in Scotland and determine the optimal frequency of screening, the justification for preschool screening and strategies for treatment.

Methods Subjects with Down's syndrome aged 1–19 years underwent capillary TSH measurement. Clinical and biochemical data were collected using proformas.

Results 5742 capillary TSH tests were performed on 1329 children in 1997–2009, increasing from 183 children from two health boards tested in 1997 to 630 from 13 health boards tested in 2009. Of 132 children referred by the screening laboratory with elevated capillary TSH, 98 (M:F ratio 1:1.2, median (range) age 8.9 (0.9–17.9) years) had adequate documentation and 76 had thyroid dysfunction (defined as venous TSH >6 mU/l), giving a prevalence of not less than 5.7%. Fifty-six (57%) had tested negative during the previous year, 8 (8%) tested positive on their first screening test and 23/67 (34%) were thyroid peroxidase autoantibody negative on initial venous blood. Two of the 13 (13%) preschool children were severely hypothyroid (venous TSH 71 and 283 mU/l). Of patients with venous TSH 6–10.9 (n=27), 11.0–20.9 (n=25) and ≥21.0 mU/l (n=24) following referral, initial/subsequent treatment with thyroxine was given in 3/8, 15/5 and 21/1, respectively.

Conclusion Capillary TSH screening in Down's syndrome is eminently feasible and should be performed annually from 1 year of age. Nearly all subjects with initial venous TSH ≥11.0 mU/l will require thyroxine treatment but most with TSH 6–10 mU/l only require surveillance initially.