2.6
그레이브스병 II: 병태생리
그레이브스병은 TSH 수용체를 활성화하는 갑상선자극 면역글로불린, 또는 TSI, 이 생성되어 갑상선호르몬(T3 및 T4)의 과도한 합성과 분비를 초래하고, 그 결과 갑상선기능항진증을 유발하는 자가면역질환입니다.
갑상선기능항진증의 모든 원인 중 그레이브스병이 가장 흔하며…
그레이브스병은 면역 체계가 내성을 유지하지 못해 형질세포가 갑상선 자극 면역글로불린(TSI)을 생성하고 방출할 때 시작됩니다.
이 항체들은 갑상선 난포 세포의 갑상선 자극 호르몬 수용체(TSH-R)에 결합하여 갑상선 자극 호르몬(TSH)의 작용을 모방합니다.
항체에 의해 수용체가 지속적으로 과자극되면, 갑상선은 정상적인 조절 없이 대량의 티록신(T4)과 트리이오도티로닌(T3)을 생성하고 방출합니다.
현미경적으로 보면 난포 세포가 키가 크고 빽빽해지며, 혈관이 증가하고 콜로이드 저장이 빠르게 고갈되어 물결 모양의 가장자리가 남습니다.
같은 면역 반응은 안도와 피부에서 TSH 수용체를 발현하는 섬유아세포를 표적으로 합니다.
눈 주변의 부종인 안와 부종, 눈 돌출인 안두 부종, 그리고 정강이에 두꺼워진 부위인 경막 점부종을 유발합니다.
혈액 내 과도한 T4와 T3는 대사율을 높여 열 생성과 심박수를 증가시킵니다.
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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.