Thyroid tumors are the most common tumors of the endocrine system and account for the first place of head and neck tumors. Clinically, they are classified into two categories, benign and malignant thyroid tumors, according to their histogenesis, degree of cell differentiation and biological characteristics. The risk factors of thyroid cancer are now highlighted.
Thyroid cancer can be divided into papillary thyroid cancer (PTC), follicular thyroid cancer (FTC), undifferentiated thyroid cancer (ATC) and medullary thyroid cancer (MTC) according to histomorphology. Among them, PTC is the most common, highly differentiated and least malignant. The incidence of PTC accounts for about 60% to 80% of thyroid cancer.
Epidemiology
Thyroid cancer is most common in young adults, with an average age of about 40 years old and a male to female ratio of about 1.0:2.5 to 1.0:3.0. Thyroid cancer accounts for 2.3% of all malignant tumors. Thyroid cancer is on the rise worldwide. According to the 2000 Tumor Registry Association report, the global incidence rate of thyroid cancer is 1.2/100,000 for men and 3.0/100,000 for women, and is on the rise year by year; a report in 2005 showed that. In 2005, it was reported that the global incidence rate was increasing by 4% per year, and it has jumped to the 8th place of common tumors in women.
Etiology
The etiology and pathogenesis of thyroid cancer are still unknown. The etiological factors associated with the development of thyroid cancer can be divided into stimulating factors for cell growth and differentiation and mutational factors for cell growth and differentiation, which act alone or together to transform thyroid cells from normal cells to tumor cells. Growth stimulating factors lead to benign tumors via TSH and are therefore often TSH-dependent; mutations, when growth stimulating factors are inhibited, are difficult to form tumors alone, but when both are present together, the tumorigenic effect is significantly enhanced.
Risk factors
The popularity of ultrasound and other diagnostic techniques and the improvement of medical personnel’s level of thyroid cancer diagnosis have significantly increased the detection rate, while ionizing radiation, iodine, hormones, other thyroid diseases and genetics may be associated with the occurrence of thyroid cancer.
1. Ionizing radiation. Ionizing radiation is significantly associated with the occurrence of thyroid cancer. It is by far one of the most definite risk factors for thyroid cancer. The incidence of thyroid cancer is linearly correlated with radiation dose. The longer the duration of radiation and the younger the age, the higher the incidence rate.
2. Abnormal iodine uptake. The relationship between iodine and thyroid cancer is still debated. The incidence of thyroid cancer is significantly higher in both iodine deficient and high iodine areas than in iodine normal areas. The co-existence of iodine deficiency and radiation promotes the occurrence of thyroid cancer.
3. Autoimmune lesions of thyroid gland. Graves’ disease is an autoimmune lesion of the thyroid gland. Some scholars found that patients with a history of Graves’ disease have a higher risk of thyroid cancer than patients with nodules without a history of thyroid disease.
4. TSH and its receptors. A number of data suggest that TSH is a promoter of thyroid tumors. Long-term TSH overproduction promotes the synthesis of cAMP and activates cAMP-dependent protein kinase signaling system, while promoting epidermal growth factor (EGF)-mediated cell proliferation. Reducing transforming growth factor β1 (TGF-β1) production, which stimulates thyroid cell growth, increases the risk of tumor development. And it has long been found clinically that drugs that inhibit TSH can reduce the recurrence rate of thyroid cancer, which further illustrates the role of TSH in promoting the occurrence of this cancer.
5.Heredity. The mode of inheritance is related to the chromosome where the gene is located. It may be autosomal dominant, recessive, or polygenic. Multiple endocrine adenomatosis, familial medullary thyroid carcinoma and familial non-medullary thyroid carcinoma with MTC are all hereditary endocrine tumors, and the mutations occur at the germline level. Patients with the above family history are prone to MTC or non-myeloid carcinoma of the thyroid.
6. Gender and female hormones. The incidence rate of thyroid cancer is significantly higher in females than males during their reproductive years. The incidence rate of thyroid cancer before puberty and after menopause is approximately the same as that of males, while the incidence rate after menopause is significantly decreasing, suggesting that estrogen plays a role in the occurrence of thyroid cancer.
7. Other. Long-term unreasonable dietary structure, poor living habits, work stress and bad emotions cause excessive acidification of the body. The overall function of human body decreases. It prompts some normal cells to change their chromosomes to take active mutation, so that tumor traits can be expressed. Irregular menstruation, early age of first pregnancy, taking birth control pills, hysterectomy and oophorectomy can all increase the risk of thyroid cancer.
It has been reported in the literature that smoking and alcohol consumption are negatively associated with the development of thyroid cancer. However, thyroid cancer patients who smoke have a worse prognosis than non-smokers. In addition, the increased incidence of thyroid cancer is also associated with the effect of environmental endocrine disruptors. Sunscreens and daily cosmetics contain different classes of endocrine disruptors. It can affect thyroid function. Promotes thyroid autoimmune abnormalities, leading to increased incidence of thyroid cancer.
Prognosis
Although the overall prognosis of thyroid cancer is good, 5-10% of patients still die from the disease. Patients with larger tumors, older age, extra-thyroidal production, airway-esophageal infiltration, and distant lymph node metastases have a worse prognosis and higher mortality.
Conclusion
In conclusion, the incidence of thyroid cancer has been rapidly increasing in recent years and its risk cannot be ignored, as there are many risk factors and complex mechanisms leading to its occurrence. In the primary prevention of thyroid cancer, on the one hand, we still need to actively search for risk factors, and on the other hand, we need to strengthen tumor-related health education for women aged 35 to 50. Help them to perform self-examination and physical examination. In addition. The strategy of early detection, early diagnosis and early treatment should be followed in the secondary and tertiary prevention.