Abstract

Objective: Little is known about the capacity, mechanisms or timing of growth in beta cell mass in humans. We sought to establish if the predominant expansion of beta cell mass in humans occurs in early childhood, and if, as in rodents, this coincides with relatively abundant beta cell replication. We also sought to establish if there is a secondary growth in beta cell mass coincident with the accelerated somatic growth in adolescence.

Research Design and Methods: To address these questions, pancreas volume was determined from abdominal computer tomographies in 135 children aged 4 weeks to 20 years, and morphometric analyses were performed in human pancreatic tissue obtained at autopsy from 46 children aged 2 weeks to 21 years.

Results: We report that (1) beta-cell mass expands by several-fold from birth to adulthood, (2) islets grow in size rather than in number during this transition, (3) the relative rate of beta-cell growth is highest in infancy and gradually declines thereafter to adulthood with no secondary accelerated growth phase during adolescence, (4) beta-cell mass (and presumably growth) is highly variable between individuals, (5) a high rate of beta cell replication is coincident with the major postnatal expansion of beta-cell mass.

Conclusions: These data imply that regulation of beta cell replication during infancy plays a major role in beta cell mass in adult humans.