Characterization of age-related changes in body weight and organ weights from birth to adolescence in humans

The pharmacokinetics and tissue dose of chemicals may differ among individu als of a population, particularly between adults and children. The adult-ch ildren differences in pharmacokinetics arise from age-related changes in th e physiological, biochemical, and physicochemical determinants of uptake an d disposition of chemicals. The objectives of this study were to review the published literature to assemble data on the human body weight and organ w eights as a function of age (specifically between birth and 18 yr old) and to analyze these data, in order to develop regression equations for calcula ting body weight and organ weights of children using age as the dependent f unction. The specific organs/tissues for which the data on age-related weig ht were obtained and analyzed include blood, adipose tissues, liver, lungs, brains, heart, kidneys, spleen, the reproductive organs (male: prostate gl and, seminal vesicle, testes, and epididymis; female: ovaries, uterus, and uterine tubes), glands (adrenal, pituitary, thymus, pancreas, and thyroid), bone marrow (total and red), intestinal tract, stomach, muscle, skin (epid ermis and dermis), and skeleton, In both male and female children, the sum of these organs is systematically lower than the body weight, and this disc repancy may be resolved with the additional availability and consideration of data on hypodermis weight. The equations and data on body weight and org an weights presented in this article should be useful for constructing age- specific, physiologically based pharmacokinetic models for children.