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格雷夫斯病 II: 病理生理学
Graves 病是一种自身免疫性疾病，其特征是产生促甲状腺刺激性免疫球蛋白，即 TSI，可激活促甲状腺激素受体，即 TSH 受体，导致甲状腺激素，即 T3 和 T4，过度合成与释放，从而引起甲状腺功能亢进症。
在甲状腺功能亢进症的所有病因中，Graves 病最为常见，可发生于任何年龄，但女性发病率更…
当免疫系统无法维持自身耐受时，格雷夫斯病（Graves' disease）便开始发生，导致浆细胞产生并释放甲状腺刺激性免疫球蛋白（thyroid-stimulating immunoglobulins，TSI）。
这些抗体与甲状腺滤泡细胞上的促甲状腺激素受体（TSH-R）结合，并模拟促甲状腺激素（TSH）的作用。
由于抗体持续过度刺激受体，甲状腺在缺乏正常调控的情况下大量产生并释放甲状腺素（T4）和三碘甲腺原氨酸（T3）。
显微镜下可见，滤泡上皮细胞变高且排列密集，血管增多，胶质储存迅速耗尽，仅留下波浪状边缘。
相同的免疫反应会靶向眼眶和皮肤中表达TSH受体的成纤维细胞。
它会引起眼周肿胀，称为眶周水肿；眼球突出，称为突眼；以及小腿前部出现增厚的斑块，称为胫前黏液性水肿。
血液中过多的T4和T3会提高代谢率，增加产热和心率。
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Q1: How do thyroid-stimulating immunoglobulins cause Graves' disease?
In Graves' disease, thyroid-stimulating immunoglobulins (TSI) are autoantibodies produced when immune tolerance fails. These antibodies bind to TSH receptors on thyroid follicular cells and mimic thyroid-stimulating hormone, continuously overstimulating the receptors. This bypasses normal feedback control, causing excessive production and release of T4 and T3 without regulation.
Q2: What microscopic changes occur in thyroid follicular cells during Graves' disease?
Thyroid follicular cells become tall and columnar, increase in number, and crowd together. Vascularity increases significantly throughout the gland. Colloid stores are rapidly depleted due to excessive hormone utilization, leaving characteristic wavy or scalloped edges on the follicles.
Q3: Why does Graves' disease cause eye protrusion and orbital swelling?
The same autoimmune response targeting thyroid cells also affects fibroblasts expressing TSH receptors in the orbit. Glycosaminoglycan deposition in orbital fibroblasts causes edema and tissue swelling, leading to periorbital edema and exophthalmos, or eye protrusion. This extrathyroidal manifestation occurs independently of thyroid hormone levels.
Q4: What is pretibial myxedema and how does it develop in Graves' disease?
Pretibial myxedema is thickened, swollen skin patches appearing on the shins. It develops when the autoimmune response targets TSH receptors on skin fibroblasts, particularly in the pretibial region. Glycosaminoglycan accumulation in these fibroblasts causes localized edema and tissue thickening characteristic of this condition.
Q5: How do elevated thyroid hormones affect metabolic rate and heart function in Graves' disease?
Excess T4 and T3 in the blood increase basal metabolic rate and heat production. Elevated thyroid hormones also increase sensitivity to catecholamines, raising heart rate and cardiac output. This hypermetabolic state produces tachycardia, palpitations, heat intolerance, and increased sweating as patients struggle to dissipate excess metabolic heat.
Q6: Why does negative feedback control fail to suppress thyroid hormone production in Graves' disease?
Although elevated T3 and T4 normally suppress pituitary TSH through negative feedback, this regulatory mechanism fails in Graves' disease. Antibody-mediated stimulation of TSH receptors persists independently of TSH levels, continuously driving thyroid hormone synthesis. The immune attack bypasses the normal hypothalamic-pituitary-thyroid axis control.
Q7: What systemic symptoms result from the hypermetabolic state in Graves' disease?
The hypermetabolic state produces weight loss despite increased appetite, fine tremors, anxiety, and hyperactivity. Patients experience tachycardia, palpitations, muscle weakness, and heat intolerance with excessive sweating. In severe cases, arrhythmias or thyroid storm may develop, representing life-threatening complications of uncontrolled hyperthyroidism.