TCM believes that when individuals who are prone to a natural deficiency of yin encounter emotional problems, such as anxiety or anger, a stagnation of liver Qi occurs. Emotional and spiritual factors have a great influence on hyperthyroidism and result in a number of hyperthyroid-related symptoms as well. This would also generate internal fire which further dries up the body's yin and blood. The liver then fails to perform its regulatory role for other organs, such as enhancing the digestive properties of the spleen. If an individual is deficient in both liver yin and kidney yin, the body is more likely to create phlegm. The phlegm obstructs the meridians causing an erratic qi circulation. When stagnant qi and phlegm collect in the neck area, they give rise to goiter formation.