[Quantitative changes of the human cell mass between the 8th and 90th year of life]

Basic anatomical and physiological data for use in radiological protection: reference values. A report of age- and gender-related differences in the anatomical and physiological characteristics of reference individuals. ICRP Publication 89

This report presents detailed information on age- and gender-related differences in the anatomical and physiological characteristics of reference individuals. These reference values provide needed input to prospective dosimetry calculations for radiation protection purposes for both workers and members of the general public. The purpose of this report is to consolidate and unify in one publication, important new information on reference anatomical and physiological values that has become available since Publication 23 was published by the ICRP in 1975. There are two aspects of this work. The first is to revise and extend the information in Publication 23 as appropriate. The second is to provide additional information on individual variation among grossly normal individuals resulting from differences in age, gender, race, or other factors. This publication collects, unifies, and expands the updated ICRP reference values for the purpose of providing a comprehensive and consistent set of age- and gender-specific reference values for anatomical and physiological features of the human body pertinent to radiation dosimetry. The reference values given in this report are based on: (a) anatomical and physiological information not published before by the ICRP; (b) recent ICRP publications containing reference value information; and (c) information in Publication 23 that is still considered valid and appropriate for radiation protection purposes. Moving from the past emphasis on 'Reference Man', the new report presents a series of reference values for both male and female subjects of six different ages: newborn, 1 year, 5 years, 10 years, 15 years, and adult. In selecting reference values, the Commission has used data on Western Europeans and North Americans because these populations have been well studied with respect to antomy, body composition, and physiology. When appropriate, comparisons are made between the chosen reference values and data from several Asian populations. The first section of the report provides summary tables of all the anatomical and physiological parameters given as reference values in this publication. These results give a comprehensive view of reference values for an individual as influenced by age and gender. The second section describes characteristics of dosimetric importance for the embryo and fetus. Information is provided on the development of the total body and the timing of appearance and development of the various organ systems. Reference values are provided on the mass of the total body and selected organs and tissues, as well as a number of physiological parameters. The third section deals with reference values of important anatomical and physiological characteristics of reference individuals from birth to adulthood. This section begins with details on the growth and composition of the total body in males and females. It then describes and quantifies anatomical and physiological characteristics of various organ systems and changes in these characteristics during growth, maturity, and pregnancy. Reference values are specified for characteristics of dosimetric importance. The final section gives a brief summary of the elemental composition of individuals. Focusing on the elements of dosimetric importance, information is presented on the body content of 13 elements: calcium, carbon, chloride, hydrogen, iodine, iron, magnesium, nitrogen, oxygen, potassium, sodium, sulphur, and phosphorus.

Human body composition: in vivo methods

In vivo methods used to study human body composition continue to be developed, along with more advanced reference models that utilize the information obtained with these technologies. Some methods are well established, with a strong physiological basis for their measurement, whereas others are much more indirect. This review has been structured from the methodological point of view to help the reader understand what can be examined with each technique. The associations between the various in vivo methods (densitometry, dilution, bioelectrical impedance and conductance, whole body counting, neutron activation, X-ray absorptiometry, computer tomography, and magnetic resonance imaging) and the five-level multicompartment model of body composition are described, along with the limitations and advantages of each method. This review also provides an overview of the present status of this field of research in human biology, including examples of reference body composition data for infants, children, adolescents, and adults.

The renal excretion of selenium

The excretion of selenium in urine was determined in West German healthy volunteers. Women excrete 17.7 +/- 4.2 micrograms Se/d and men 19.0 +/- 9.0 micrograms Se/d. The daily selenium excretion per gram creatinine is 13.5 +/- 3.8 micrograms Se/g crea for women and 9.8 +/- 3.3 micrograms Se/g crea for men. The clearance of selenium from the plasma is calculated with 0.18 mL/min. The selenium excretion per day is positively correlated with the 24 h excretion of urea and creatinine. The correlation of the selenium excretion with the urea excretion is most probably owing to the fact that the selenium intake of West Germans is linked primarily to foods with high protein contents. That the selenium excretion is directly correlated with the creatinine excretion is an indicator that the muscle, which accounts for nearly 50% of the whole body selenium in West German adults, influences the selenium excretion in urine. The positive correlation of the selenium excretion with the potassium excretion also indicates that the muscle mass contributes significantly to the selenium excretion in urine. Another indicator that the selenium excretion is influenced by the muscle is that after intensive muscular activity (running), selenium excretion is enhanced. The 24 h selenium excretion is dependent on the glomerular filtration rate of the kidney characterized by the creatinine clearance. This result is important, because if the selenium excretion is used as parameter for the selenium status of humans, the kidney function should be known. This is a limitation for the use of the urinary selenium excretion as parameter for the selenium status. This is especially important for patients whose glomerular filtration rate is low. The 24 h selenium excretion is further influenced by the 24 h urine volume. Selenium losses via urine may be concomitant with protein losses in urine.

Gynecomastia in a hospitalized male population

Two hundred fourteen hospitalized adult men, aged 27 to 92, were examined for the presence of palpable gynecomastia. The overall prevalence was 65 percent. Gynecomastia was bilateral in all but 11 subjects. The prevalence was greatest in the 50 to 69-year-old group (72 percent). It was lower in the 70- to 89-year-old (47 percent, p less than 0.01) and the 30- to 49-year-old (54 percent, p less than 0.05) groups. The prevalence of gynecomastia increased with body mass index. More than 80 percent of those with a body mass index of 25 kg/m2 or greater had gynecomastia. The diameter of breast tissue also increased with increasing body mass index (r = 0.52, p less than 0.001). The decreased prevalence of gynecomastia after the seventh decade could be explained by the lower body mass index in this group. The youngest group did not have a lower body mass index; an independent age factor appeared to be present. Because of the high overall prevalence of gynecomastia, independent effects of diseases or medications could not be determined. It is concluded that palpable bilateral gynecomastia is present in most older men, is correlated with the amount of body fat, and does not require clinical evaluation unless symptomatic or of recent onset.

Electrolyte disorders in the elderly

Normal human ageing impairs homeostatic mechanisms in such a way as to exaggerate and prolong the effects of stress. Thus, an event--pathological or traumatic--which produces a trivial change in plasma electrolytes of young people may produce major oscillations of plasma levels in the elderly, which take much longer to return to 'normal levels'. This is especially apparent with perturbations in the plasma levels of sodium and potassium, mainly due to changes in renal function and neurohumeral mechanisms which occur with increasing age. Paradoxically this does not mean that the clinician should be over-enthusiastic in attempting to correct electrolyte imbalance because, for the same reasons, the danger of over-treatment producing the opposite and equally dangerous electrolyte imbalance is ever-present. Indeed, in clinical practice most electrolyte disturbances in old age are iatrogenic in origin. Cautious patience and vigilance should be the clinical approach with elderly patients. A high index of suspicion should lead to a careful appraisal of the drug (diuretic, intravenous fluid) and environmental (dehydration) aetiology of most electrolyte disturbances in old age.

Assessment and conservative management of the overfat adolescent

With the increasing incidence of obesity among adolescents, physicians are often asked about weight reduction programs and "ideal" body weights for patients of varying biological maturities. Morbidly obese patients are easily diagnosed; however, little differentiation is made in assessing adolescents who are considered overweight vs. overfat as defined by current growth charts. This article provides an overview of methods and norms for assessing body weight and energy needs within the context of a clinic setting and discusses the advantages and disadvantages of conservative treatment approaches: diet, exercise, and behavior modification.

Human body composition as related to surface area

There is a linear relationship between extracellular fluid and body surface area in man. During growth the body cell mass, fat-free solids, and body fat proportions of body weight increase while the extracellular fluid fraction decreases. Growth stops in men as soon as the body cell mass reaches 22.5 kg/m2 body surface area and in women when it reaches 16.9 kg/m5. The non-muscle cell mass and the muscle cell mass reach a 1:4 ratio in men whereas in women a 1:35 proportion--which is more favorable for pregnancy and lactation--is reached. The body composition of the newborn and the infant have fetal characteristics with a low body fat: surface area ratio and a low non-muscle cell mass: surface area ratio. The basal metabolic rate depends on the amount of non-muscle mass present, and the total energy change depends on body cell mass. This has been established by measurements of total body potassium, thiosulfate space, total body sodium, 24 h urine creatinine values and basal metabolic rate.

Body composition. Prediction of normal body potassium, body water and body fat in adults on the basis of body height, body weight and age

In 134 males and 242 females, aged 20-70 years, most of them randomly selected from population studies, the body composition was estimated from the measurements of body height (BH), body weight (BW), total body potassium (TBK) and total body water (TBW). TBK was measured with isotope dilution technique using 42K or determined as 40K in a whole body counter. TBW was determined with an isotope dilution technique using tritiated water, assayed in urine or plasma. From these data, body cell mass (BCM), intra- and extra-cellular water (ICW and ECW, resp.) and body fat (BF) were calculated for each individual. Significant correlations were found between age versus TBK, ECW, BF and ECW/ICW; between BW versus TBK, TBW, ECW, BF and ECW/ICW; (females only) and between BH versus TBK, TBW, ECW (females only) and ECW/ICW. For the prediction of TBK, TBW and BF, multiple regression equations based on BW, BH and age are given. These equations are also presented diagrammatically. The problems with the methods used are considered as well as the applicability of the formulas for the calculation of BCM etc. The predictive value of the results when both TBW and TBK are used for the calculation of body composition data is discussed and compared with similar results, based on TBW or TBK only. It is concluded, that the most reliable method for calculation of BF is to estimate both TBW and TBK.