糖尿病是病人无法生产和/或利用胰岛素,导致高血糖的一组疾病。注意糖尿病不要与尿崩症混淆。尿崩症是一种更罕见的疾病,虽然与糖尿病症状相似,但病因不同。虽然这两种疾病含有着“糖尿病”的意义 (这意味着尿液生成增加),但应用糖尿病这个称呼本身,往往是用来专指糖尿病,并且也是本篇文章所指。
据美国国立糖尿病、消化道和肾脏病研究所统计(2005年数据),在美国约2000万人患糖尿病,且多达600万人尚未认识到糖尿病正在影响他们的健康。糖尿病破坏了正常的胰岛素和葡萄糖的平衡。餐后碳水化合物通常被分解成葡萄糖和其它单糖,这会导致血糖水平上升,刺激胰腺释放胰岛素进入血液。
胰岛素是胰腺β细胞合成的一种激素。它调节葡萄糖的运输,使葡萄糖进入大多数的体细胞,并与另一胰腺激素-胰高血糖素共同作用,使血糖水平维持在一个狭窄的范围内。如果胰岛素缺乏或作用无效,又或者人体细胞对胰岛素作用产生抵抗(胰岛素抵抗),血液中保持很高的血糖水平,而人体细胞却处于“饥饿”状态。根据胰岛素缺乏的程度可能会引起急性和慢性的疾病。机体的大多数组织依赖葡萄糖提供能量而工作,少数组织(如大脑和神经系统)则完全依赖于胰岛素介导的运输。
急性高血糖症是一个内科急症。机体试图通过增加排尿消除血液系统中多余的血糖。这个过程可能会导致脱水以及由于尿液中钠和钾丢失而破坏人体的电解质平衡。由于胰岛素严重缺乏导致葡萄糖不能提供给细胞,人体可能会尝试通过脂肪酸代谢来提供替代能量。这种低效过程导致了酮体的产生而破坏了人体的酸碱平衡,形成了酮症酸中毒。任其发展,急性高血糖可导致严重脱水、意识丧失、甚至死亡。
血糖水平随着时间的推移而上升,其水平缓慢提升最初并没有引起病人的注意。机体试图增加胰岛素的产生和增加尿液中葡萄糖的排泄来控制血液中的血糖含量。当机体不再能够代偿较高水平的血糖时,就会出现症状。慢性高血糖可造成整个身体的血管、神经和器官的长期损害,并可能导致其它疾病,如肾功能衰竭、失明、中风和心血管疾病;糖尿病也经常会导致双下肢的血液循环障碍。高血糖损害是累积的,可能在病人知道自己有糖尿病之前就已经开始了。越早发现和治疗,越能最大限度地减少并发症的发生。
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