Kidney disease related to autoimmune thyroid disease

　　1. Etiology

　　Autoimmune thyroid disease (AITD) is a thyroid disease caused by autoimmune disorder, in which autoantibodies against thyroid antigens can be detected in the patient's blood, including thyroglobulin antibody and thyroid microsomal antibody, etc. Patients may also have mild proteinuria, and a few may even develop nephrotic syndrome. A literature reported 85 cases of AITD patients, with proteinuria as high as 40%. Studies suggest that the occurrence of such proteinuria may be related to autoimmune factors. Many renal biopsies of AITD patients with proteinuria have shown thyroid antigen deposition in the renal tissue, suggesting that it may be due to the deposition of thyroid antigen-antibody complexes in the renal tissue through the blood circulation, leading to immune complex nephritis.

　　2. Pathogenesis

　　Foreign scholars believe that the pathogenesis of membranous nephropathy in AITD may be the deposition of thyroglobulin and thyroid microsome antigens outside the glomerular basement membrane, leading to the formation of in situ immune complexes, and some cases may involve the mechanism of circulating immune complexes.

　　1. Hypothyroidism:This is a relatively prominent complication after 131 iodine treatment. According to a series of studies abroad, the incidence of hypothyroidism in the constant dose group, that is, after the administration of 3.7MBq (100μCi) of 131 iodine per gram of thyroid, is about 5% to 10% in the first year, and it increases by 2% to 3% each year to 30% to 70% after 10 years of treatment. In recent years, the incidence of hypothyroidism has also increased significantly in China, due to the improved diagnosis sensitivity of hypothyroidism after the implementation of serum TSH radioimmunoassay. According to our follow-up of 64 cases from 1958 to 1980, the incidence of hypothyroidism after 131 iodine treatment was 25% for 2 to 5 years, 50% for 6 to 10 years, 83.5% for 16 to 20 years, and the total incidence of hypothyroidism was 52.08%. There are three possible causes of hypothyroidism: first, the dose of 131 iodine treatment is too high, causing excessive destruction of thyroid tissue. The second speculation is that ionizing radiation may cause damage to the cell nucleus, resulting in inability to divide and regenerate, and the longer the time, the more减退 in thyroid function. The third believes that it is due to autoimmune reactions.

　　2. Carcinogenic issues:For more than 30 years of clinical application of this therapy, the incidence of leukemia and thyroid cancer, compared with the natural incidence of these two diseases, does not increase. Some people have analyzed the incidence of thyroid cancer in three therapies: the 131 iodine treatment group (22714 cases) with 0.1%, the surgical operation group (11732 cases) with 0.5%, and the antithyroid drug group (1238 cases) with 0.3%. Another group reported that among 60000 cases treated with 131 iodine, 18 cases of leukemia occurred, which is not higher than the natural incidence of leukemia in the general population. To date, there have been approximately 50,000 cases of 131 iodine treatment for hyperthyroidism in China, with only 2 cases of leukemia reported, and the incidence is not higher than the natural incidence in the general population. Moreover, both cases occurred about 1 year after 131 iodine treatment, with a short onset time. Whether it is directly related to 131 iodine treatment is still questionable. Since young patients are sensitive to ionizing radiation, some reports have shown that the incidence of thyroid cancer is high in infants and children who have received X-ray treatment in the neck, so for prudence, it is advisable for adolescents under the age of 25 to choose other treatment methods.

　　3. Genetic effects:Patients with hyperthyroidism do not experience any impact on their fertility after treatment with 131 iodine, and the incidence of congenital malformations, stillbirths, and premature infants in their offspring has not increased. The incidence of infertility is not significantly different from that of the general population. Foreign data show that many patients who have been treated with 131 iodine have had healthy offspring, and even some female patients who were previously infertile due to endocrine disorders caused by hyperthyroidism have given birth to children after treatment. Of course, some people have observed that there are chromosomal variations after 131 iodine treatment, but they can gradually return to normal, so the biological and clinical significance of chromosomal variation caused by 131 iodine treatment still needs to be further explored. Although it is currently believed that from a genetic perspective, 131 iodine treatment increases the risk of gene mutation and chromosomal abnormalities, considering the long-term effects of ionizing radiation, genetic effects also need to be followed up for a long time to draw correct conclusions. In order to ensure the health of the next generation and the children of the next generation, it is reasonable to list pregnancy as a contraindication for 131 iodine treatment.

　　4. Exophthalmos exacerbation:It is only seen in a small number of patients. Most patients have varying degrees of improvement after treatment.

　　The main manifestations are clinical symptoms of AITD and proteinuria, which is usually mild, but sometimes it can even manifest as nephrotic syndrome. AITD and proteinuria can occur simultaneously or sequentially, sometimes AITD appears first, and sometimes proteinuria appears first, and the interval between the two can be up to more than 10 years.

　　This disease belongs to autoimmune diseases, caused by autoimmune disorders leading to thyroid diseases. Autoantibodies against thyroid antigens can be detected in the patient's blood, including thyroglobulin antibodies and thyroid microsomal antibodies, etc. Most autoimmune diseases can be complicated by renal injury, so for those who have developed autoimmune thyroiditis, active treatment should be carried out to maintain thyroid function at a stable level.

　　Laboratory manifestations of nephrotic syndrome may be present, with proteinuria and AITD occurring simultaneously or sequentially, occasionally accompanied by microscopic hematuria, and most often without hypertension or renal dysfunction.

　　Renal biopsy in patients with AITD-related nephrotic syndrome, the most common pathological type is membranous nephropathy, and there may also be mesangial proliferative glomerulonephritis and focal glomerulosclerosis changes. The specific change is that thyroid antigens are deposited in the renal tissue biopsy.

　　1. For kidney disease related to autoimmune thyroid diseases, it is important to pay attention to a low-salt, light diet, avoid spicy and刺激性 foods, and vegetables, fruits, and soy products are indispensable.

　　2. Pay attention to rest, avoid fatigue, maintain a good attitude, avoid tension and stress, which is conducive to the recovery of the body.

　　3. Actively cooperate with the doctor's treatment, adhere to standardized medication, and can be supplemented with traditional Chinese medicine adjustment when necessary.

　　The treatment of nephrotic syndrome related to autoimmune thyroid diseases (AITD) is currently lacking a unified understanding. Foreign literature reports that immunosuppressants and thyroidectomy may be effective. However, more emphasis should be placed on the comprehensive treatment of AITD itself. Since a large amount of proteinuria during nephrotic syndrome can cause the loss of thyroid-binding globulin, it often exacerbates hypothyroidism, so the dose of thyroid replacement therapy for such patients usually needs to be increased. The clearance of thyroid antibodies and abnormal thyroid antigens is the main part of the treatment.

　　1. During Graves' disease, due to the mild immunosuppressive effect of pyrimidine and imidazole drugs used to treat hyperthyroidism, the level of thyroid autoantibodies in the blood circulation can be reduced, thereby reducing proteinuria.

　　2. The application of immunosuppressants in combination with corticosteroids and azathioprine (Imuran) can reduce proteinuria in some patients.

　　3. The effect of thyroidectomy on proteinuria is unclear, but in the first case of Graves' disease complicated with nephrotic syndrome, the long-term administration of methimazole (Tapazole) was ineffective, and the thyroid was finally removed, and after 11 months of follow-up, proteinuria decreased significantly, and there was no change in glomerular filtration rate. It is important to determine the timing of thyroidectomy, and its relief is almost limited to stage I to II membranous nephritis patients.

　　4. The efficacy of radioactive iodine treatment for proteinuria is not clear, and it may even worsen proteinuria.