Serum Iron and Iron-Binding Capacity in Adolescents: I. Standard Values

Abstract

An analysis of serum iron concentration, iron-binding capacity and other related variables obtained on 160 male and 162 female “normal” adolescents with hemoglobin levels of 12.0 gm. per cent and higher revealed the following: (1) A high degree of variability exists within our adolescent series with respect to serum iron and iron-binding levels. (2) The analysis of the data for sex differences showed the boys to have higher serum iron levels than the girls, slightly lower unsaturated iron-binding capacities and a greater percentage saturation of the circulating tnansferrin, as well as higher mean hemoglobin levels, hematocrit values and mean corpuscular hemoglobin concentration. (3) Age is positively correlated in boys with respect to serum iron, percentage saturation, hemoglobin and hematocrit and in both boys and girls with height, weight and surface area. For girls only, negative associations with age occur with serum iron, percentage saturation and ponderal index. (4) After the effect of age is removed, serum iron has the highest order of interrelationship with height, weight and surface area in girls. Serum iron is unrelated to total iron-binding capacity but negatively related to unsaturated iron-binding capacity. After corrections for age, height and weights, a low order of relationship appears to remain between serum iron and hemoglobin in girls. (5) Comparison of premenarche and postmenarche girls of the same age showed the girls maturing late to have higher serum iron levels, greater unsaturated and total iron-binding capacities, and lower percentage saturation than those maturing early. Menstrual blood loss does not appear to exert a significant influence on the differentiations between the two groups. (6) The adolescents display lower serum iron levels, higher unsaturated and total iron-binding capacities, and lower percentage saturation values than normal adults. (7) About a third of the adolescents have serum iron concentrations below the normal adult level of 75µg. per 100 ml. and above the unsaturated iron-binding capacity adult level of 300µg. per 100 ml. A sixth of the adolescent boys and the same proportion of girls exhibit the combination of a “subnormal” serum iron level below 75µg. per cent and an “elevated” unsaturated iron binding capacity of 300µg. per cent or more. The implications of this finding in adolescence is discussed. This report provides a basis for the development of transport iron standards in adolescence and indicates that further studies in the normal variability of these hematologic characteristics in other populations are desirable.