The first accurate measurement of somatostatin concentration in human blood

The primary structure of the cyclic peptide which inhibits the secretion of growth hormone from the pituitary gland was first reported in 1973 by Roger Guillemin and co-workers, through extraction of the ovine hypothalamus. Later named somatostatin, discovery of this and other hypothalamic hormones resulted in Guillemin being jointly awarded the Nobel Prize for Physiology or Medicine in 1977. Since then, at least 19 studies have been published on the measurement of somatostatin concentration in mammalian blood plasma. Unfortunately, every single reported measurement is wrong, many grossly so, the values ranging from 2.5-360 pg/mL and averaging 60 pg/mL. This current study will detail the measures taken to arrest endogenous somatostatin degradation, selection of a suitable internal standard, relevant technical innovations, and development of LC-MS/MS methods on state-of-the-art instrumentation. Finally, the newly developed analytical method was applied to a pilot study employing ten healthy human subjects. Fasting somatostatin levels were 0.87 ± 0.03 and 0.59 ± 0.11 ng/mL in the male and female cohorts respectively. These concentrations increased to 1.44 ± 0.07 (M) and 1.33 ± 0.18 ng/mL (F) following breakfast.