Nutrition Department, Medical Research Institute, Colombo, Sri Lanka.
Department of Medicine, Section of Endocrinology, Cwm Taf University Health Board, Prince Charles Hospital, Merthyr Tydfil, United Kingdom.
Thyroid. 2021 Jul;31(7):1105-1113. doi: 10.1089/thy.2020.0798. Epub 2021 Feb 15.
Sri Lanka introduced universal salt iodization (USI) in 1995 after which we demonstrated a high thyroglobulin antibody (TgAb) prevalence in 1998. However, it is unclear whether thyroid autoimmunity persists in the long term in populations exposed to sustained USI and whether such populations have an excess of thyroid dysfunction. We evaluated the prevalence of thyroid autoantibodies and dysfunction in Sri Lankan children and adolescents after more than two decades of sustained USI. We selected 10- to 18-year-old subjects of both sexes (randomized cluster sampling) from all 9 provinces of Sri Lanka in this cross-sectional study. Blood, urine, and anthropometric data were collected and thyroid ultrasound scans were performed. Validated statistical methods were used to derive local population-specific reference ranges for all thyroid parameters. We also measured urine iodine concentration (UIC), salt, and water iodine concentrations. Blood and urine samples from 2507 and 2473 subjects respectively, and ultrasound scans from 882 subjects were analyzed. Population-derived upper limits for thyroid peroxidase antibody (TPOAb) and TgAb, and reference ranges for triiodothyronine, thyroxine, and thyrotropin (total and age-year-related groups) were significantly different from manufacturer's reference ranges. Using these derived ranges, the prevalence of TPOAb was 10.3% and TgAb was 6.4%. Of the TPOAb-positive subjects, TPOAb were of low concentration in 66.2% (1-3 times the upper limit of the reference range [ULRR]) and showed the strongest association with subclinical hypothyroidism (SCH) at the highest concentrations (>4 ULRR). The prevalence of SCH was 3%. Median UIC (interquartile range) was 138.5 μg/L (79.4-219.0) with regional variability, and median thyroglobulin was 8.3 ng/mL (4.1-13.5). Goiter prevalence was 0.6% and 1.93% (thyroid volume compared to age and body surface area, respectively). Salt and water iodine concentrations were satisfactory. Sri Lanka has safely and effectively implemented USI with good sources of iodine, leading to sustained iodine sufficiency over more than two decades. The early postiodization TgAb surge (42.1%) has settled (6.4%), and despite a persistently high TPOAb prevalence (10.3%), SCH prevalence remains low (3%). Further studies should be undertaken to monitor thyroid autoimmune dysfunction in Sri Lankan children, using age-specific, population-derived reference ranges.
斯里兰卡于 1995 年引入全民食盐碘化（USI），随后我们在 1998 年发现甲状腺球蛋白抗体（TgAb）的高患病率。然而，在持续 USI 暴露下，甲状腺自身免疫是否在人群中长期存在，以及此类人群是否存在甲状腺功能障碍的增加，尚不清楚。我们评估了在持续 USI 超过 20 年后，斯里兰卡儿童和青少年的甲状腺自身抗体和功能障碍的患病率。在这项横断面研究中，我们从斯里兰卡的 9 个省中随机抽取了 10-18 岁的男女受试者（随机聚类抽样）。采集了血液、尿液和人体测量学数据，并进行了甲状腺超声检查。使用经过验证的统计方法得出了所有甲状腺参数的当地人群特异性参考范围。我们还测量了尿碘浓度（UIC）、盐和水碘浓度。分别分析了 2507 名和 2473 名受试者的血液和尿液样本，以及 882 名受试者的超声扫描结果。甲状腺过氧化物酶抗体（TPOAb）和 TgAb 的人群衍生上限，以及三碘甲状腺原氨酸、甲状腺素和促甲状腺激素（总甲状腺和年龄相关组）的参考范围与制造商的参考范围明显不同。使用这些衍生范围，TPOAb 的患病率为 10.3%，TgAb 为 6.4%。在 TPOAb 阳性的受试者中，66.2%（参考范围上限的 1-3 倍[URLR]）的 TPOAb 浓度较低，与最高浓度时的亚临床甲状腺功能减退症（SCH）相关性最强（>4 ULRR）。SCH 的患病率为 3%。中位 UIC（四分位间距）为 138.5μg/L（79.4-219.0），存在区域变异性，中位甲状腺球蛋白为 8.3ng/mL（4.1-13.5）。甲状腺肿的患病率为 0.6%和 1.93%（分别为甲状腺体积与年龄和体表面积的比值）。盐和水碘浓度令人满意。斯里兰卡安全有效地实施了 USI，有良好的碘源，20 多年来一直保持碘充足。碘化物后的早期 TgAb 激增（42.1%）已经稳定（6.4%），尽管 TPOAb 的高患病率（10.3%）持续存在，但 SCH 的患病率仍然很低（3%）。应该进行进一步的研究，使用年龄特异性、人群特异性参考范围来监测斯里兰卡儿童的甲状腺自身免疫功能障碍。
