Hashimoto’s disease is classified as an autoimmune disorder, which occurs when the body's immune system attacks and destroys healthy body tissue by mistake. It can be part of the Polyglandular Autoimmune Syndrome type 2 with autoimmune adrenal deficiency and type-1 diabetes (Mincer, 2022). Hashimoto’s disease occurs when immune-system cells lead to the death of the thyroid’s hormone-producing cells and usually results in a decline in hormone production (hypothyroidism). (Mayo Clinic , 2022). 

Up till now, it is still unclear as to what causes the immune system to attack thyroid cells. Some of these factors have been identified, whereas some are still unknown. Research shows that the onset of Hashimoto’s disease may be related to genetic factors. Variations in several genes have been studied as possible risk factors for Hashimoto thyroiditis. Some of these genes are part of a family called the human leukocyte antigen (HLA) complex (MedlinePlus Genetic, n.d.) The HLA complex aids the immune system in differentiating between the body's own proteins from proteins made by foreign invaders (such as bacteria and viruses). Other genes that have been associated with Hashimoto disease help regulate the immune system or are involved in normal thyroid function. However, it is important to note that majority of the genetic variations that have been identified to have a small impact on a person’s overall risk of developing this condition.   

Other than that, non genetic factors may also contribute to Hashimoto’s disease. These factors may trigger the condition in people who are at risk, although the mechanism is unclear. Potential triggers include changes in sex hormones (especially in women), viral infections, certain medications, exposure to ionising radiation, eating large amounts of food that contain animal protein, and an excessive iodine consumption (which is a substance that is involved in the production of thyroid hormones). It is also important to note that interactions between environmental and genetic factors may also play a role in contributing to Hashimoto’s disease.