Any quantification of the amounts or proportions of proteins, lipids, minerals, nutrients, gases, or other substances in a specified sample of pancreatic islet tissue, i.e. one or more of the islets of Langerhans, the small, encapsulated, irregular, microscopic structures scattered throughout the pancreas and comprising its endocrine portion. The pancreas is the elongated, racemose gland containing both endocrine and exocrine elements which secretes hormones such as insulin and glucagon internally and digestive enzymes externally.