Gang Bing (died 1410): patron saint of eunuchs in China who castrated himself to demonstrate his loyalty to the Yongle Emperor. Wang Zhen (died 1449): first Ming eunuch with much power; see Tumu Crisis. Kim Cheo Seon (1421–1505): one of the most famous eunuchs in Korean Joseon Dynasty, ably served kings in the Joseon dynasty. His life is the subject of a historical drama in South Korea. Liu Jin (1451–1510): corrupt eunuch official of the Ming dynasty and de facto emperor, member of the Eight Tigers. Judar Pasha (1562–1606): a Spanish eunuch who became the head of the Moroccan invasion force into the Songhai Empire. Wei Zhongxian (1568–1627): eunuch of the Ming dynasty, considered the most powerful eunuch in Chinese history. Senesino (1686–1758): Italian contralto castrato singer. Farinelli (1705–1782): Italian soprano castrato singer. Giusto Fernando Tenducci (c. 1736–1790): Italian soprano castrato singer. Mohammad Khan Qajar (1742–1797): chief of the Qajar tribe. He became the King/Shah of Persia in 1794 and established the Qajar dynasty. Lê Văn Duyệt (c. 1763–1832): Vietnamese eunuch, military strategist and government official (not a true eunuch, he was born a hermaphrodite). Thomas P. "Boston" Corbett (b. 1832; presumed dead 1894): killer of John Wilkes Booth, the assassin of Abraham Lincoln, who castrated himself to avoid temptation from prostitutes. Li Lianying (1848–1911): a despotic eunuch of the Qing dynasty. Alessandro Moreschi (1858–1922): Italian castrato singer, the only one to make recordings.
Causes
The slowing of the bodys basal metabolic rate associated with hypothyroidism
Pernicious anemia where there is antibody production against parietal cells which normally produce gastric acid. The use of antacids or drugs that decrease gastric acid production (such as H2-receptor antagonists) or transport (such as proton pump inhibitors). A symptom of rare diseases such as mucolipidosis (type IV). A symptom of Helicobacter pylori infection which neutralizes and decreases secretion of gastric acid to aid its survival in the stomach. A symptom of atrophic gastritis or of stomach cancer. Radiation therapy involving the stomach. Gastric bypass procedures such as a duodenal switch and RNY, where the largest acid producing parts of the stomach are either removed, or blinded. VIPomas (vasoactive intestinal peptides) and somatostatinomas are both islet cell tumors of the pancreas. Pellagra, caused by niacin deficiency. Chloride, sodium, potassium, zinc and/or iodine deficiency, as these elements are needed to produce adequate levels of stomach acid (HCl). Sjögrens syndrome, an autoimmune disorder that destroys many of the bodys moisture-producing enzymes
Ménétriers disease, characterized by hyperplasia of mucous cells in the stomach also causing excess protein loss, leading to hypoalbuminemia. Presents with abdominal pain and edema

Risk Factors
Age
It was found that the incidence of achlorhydria in patients under the age of 60 was around 2.3%, whereas it was 5% in patients over the age of 60. In a persons 30s, the prevalence is about 2.5%, and increases to 12% in a persons 80s. An absence of hydrochloric acid increases with advancing age.