Gauchez Anne-Sophie, Pizzo Magali, Alcaraz-Galvain Dany, Chikh Karim, Orgiazzi Jacques, Brabant Georg, Ronin Catherine, Charrié Anne
Laboratoire du Service de Médecine Nucléaire, Centre Hospitalier de Chambéry, 73000 Chambéry, France.
J Thyroid Res. 2010 Jul 14;2010:703978. doi: 10.4061/2010/703978.
Background. For unknown reasons, the prevalence of thyroid autoimmune disorders is higher in patients with Down's syndrome than in the general population. The present case strongly supports a recent evaluation of propagating screening for thyroid disease in this group of patients to assure early diagnosis of hypothyroidism. Methods. In a 25-year-old man diagnosed with Down's syndrome, clinical manifestations of hypothyroidism were lacking, but profound biochemical abnormalities were found with particularly high levels of thyroid stimulating hormone (TSH). Antigenic properties of TSH were characterized using a panel of anti-TSH antibodies. Results. Technical problems not infrequently associated with TSH measurements are convincingly ruled out. Antigenic characterization of the patient's circulating TSH revealed circulating forms of TSH different from pituitary TSH which closely resembled TSH recombinant human hormone. Conclusions. It appears counterintuitive that the bioactivity of TSH decreases in the hypothyroid state as higher bioactivity of TSH is anticipated in hypothyroidism promoted by an increased hypothalamic TRH drive. In contrast, diminished negative thyroid hormone feedback will enhance posttranslational glycosylation of TSH subunits and increase sialylation of the carbohydrate side chains. Both exert a negative effect on TSH bioactivity, only compensated by the very high levels of the hormone as in the present case.
背景。不明原因的是，唐氏综合征患者甲状腺自身免疫性疾病的患病率高于普通人群。本病例有力地支持了近期对该组患者进行甲状腺疾病传播性筛查的评估，以确保早期诊断甲状腺功能减退症。方法。在一名诊断为唐氏综合征的25岁男性中，缺乏甲状腺功能减退症的临床表现，但发现了严重的生化异常，尤其是促甲状腺激素（TSH）水平特别高。使用一组抗TSH抗体对TSH的抗原特性进行了表征。结果。令人信服地排除了与TSH测量不常相关的技术问题。对患者循环TSH的抗原表征显示，循环形式的TSH与垂体TSH不同，与重组人TSH激素非常相似。结论。甲状腺功能减退状态下TSH生物活性降低似乎有悖常理，因为在由下丘脑TRH驱动增加所促进的甲状腺功能减退症中，预计TSH具有更高的生物活性。相反，甲状腺激素负反馈减弱会增强TSH亚基的翻译后糖基化，并增加碳水化合物侧链的唾液酸化。两者都会对TSH生物活性产生负面影响，只有像本病例中那样激素水平非常高才能得到补偿。
