label: Decreased small intestinal mucosa lactase level
label_lc: decreased small intestinal mucosa lactase level
description: "Lactase is produced in the small intestine in humans, Lactase is a member of the beta-galactosidase family of enzymes, and hydrolyzes D-lactose to form D-galactose and D-glucose, which can be absorbed by the small intestine. There are many ways of assessing lactase activity. In one test, an endoscopic biopsy from the postbulbar duodenum is incubated with lactose on a test plate, and a color reaction develops within 20 min as a result of hydrolyzed lactose (a positive result) in patients with normolactasia, whereas no reaction (a negative result) develops in patients with severe hypolactasia. Other, less direct, tests include the hydrogen breath test, and blood tests following lactose challenges."