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Rev. bras. epidemiol. vol.10 n.3 São Paulo Sep. 2007
LETTER TO THE EDITOR
Article: Mariath AB, Henn R, Matos CH, Lacerda LLV, Grilo LP. Prevalência de anemia e de níveis séricos de hemoglobina em adolescentes segundo estágio de maturidade sexual. (Prevalence of anemia and hemoglobin serum levels in adolescents according to sexual maturation stage). Revista Brasileira de Epidemiologia 2006; 9(4): 454-461.
Maria Sylvia de Souza VitalleI; Josefina Aparecida Pellegrini BragaII
de Atendimento e Apoio ao Adolescente da Disciplina de Especialidades Pediátricas
do Departamento de Pediatria da Unifesp EPM
IISetor de Hematologia Pediátrica da Disciplina de Especialidades Pediátricas do Departamento de Pediatria da Unifesp - EPM
We would like to congratulate the authors of the excellent paper "Prevalence of anemia and hemoglobin serum levels in adolescents according to sexual maturation stage"1 for their outstanding quality and contribution, and at the same time, we would like to clarify a few points that seem biased interpretation to us.
In the second paragraph of the discussion, they say, incorrectly, that, "Although the present study did not evaluate the food intake of adolescents, it looks like this is the only reason accounting for the higher averages of hemoglobin levels in males". Even though we know that food intake with insufficient iron content is the main reason for iron deficiency anemia and that there is no encompassing Brazilian study on the subject, it looks like the prevalence of anemia is not high among adolescents in our society.
In adolescence, males are expected to have a higher Hb level than that of females, because prostaglandins facilitate erythropoietic activity, both directly (PGE1) and through cyclic AMP (PGE2). Androgens stimulate the activity of erythropoietin through an increase in production through facilitation in erythroid stem cells. Conversely, estrogens inhibit the effects of erythropoietin2. That is the reason for the standardizations showing that, after the age of 15 years, hemoglobin cutoff points for males and females change2,3.
They worked with a wide age group, from 10 to 18 years, although on average, they focused around 12-13 years of age. They also showed, in Table 4, that the difference between the distribution of average Hb levels and the pubertal stage occurs in phases IV and V, which are later development pauses, when boys are at the peak of the growth spurt or are already past it; and it is known that hormonal changes will have already taken place then, differentiating genders, as previously explained.
Higher levels of Hb are, therefore, expected as both genders evolve through pubertal stages. We should remember, that, until 15 years of age, the differences between hemoglobin (Hb) levels in males and females are minor; and from then on these differences grow (0.5 to 1g/10mL) due to the increase in the production of testosterone and to the differences in sexual maturation4,5 .
It is possible to note, in both papers quoted, Frutuoso et al.6 and Iuliano et al.7, that the samples comprise adolescents with less than 15 years; therefore, although one might argue about the small size of the sample, this detail alone would already justify the fact they did not find statistically significant differences among average Hb levels between genders, even though they found a growing trend directly related to pubertal development.
Due to the changes in the nutritional needs of adolescents, up to the beginning of menstruation in girls, and the hormonal changes resulting from puberty, there are differences in hemoglobin concentrations in both genders, at different ages and in different phases, considering pre-pubertal and pubertal adolescents8,9. However, as to the different levels of hemoglobin, it is expected in boys, as pubertal staging advances, especially due to the hormonal issues involved, and diet is not the only factor to blame, as the paper suggests. Iron is used in the treatment of iron deficiency anemias. Iron is given to patients with normal blood levels to increase the "iron reserves" of the body, and not to increase the amount of red blood cells or hemoglobin above their normal physiological levels9,10. Therefore, along the same line of thought, increasing the dietary bioavailability of iron will not increase hemoglobin levels above normal physiological levels.
1. Mariath AB, Henn R, Matos CH, Lacerda LLV, Grillo LP. Prevalência de anemia e níveis séricos de hemoglobina em adolescentes segundo estágio de maturidade sexual. Rev Bras Epidemiol 2006; 9(4): 454-61.
2. Nathan GD, Orkin SH. Appendices Reference values in infancy and childhood. In: Nathan and Oski's. Hematology of Infancy and childhood. 5 ed. Philadelphia: WB Saunders; 1998. p. 1893.
3. Powers LW. Diagnostic hematology clinic and technical principles. CV Mooby Company. 1989.
4. Daniel Jr WP, Rowland AM. Hemoglobin and hematocrit values of adolescents. Clin Pediatric 1969; 8: 181.
5. Daniel Jr WP. Hematocrit: maturity relationship in adolescence. Pediatrics. 1973; 52: 358.
6. Frutuoso MFP, Vigantzky VA, Gambardella AMD. Níveis séricos de hemoglobina em adolescentes segundo estágio de maturação sexual. Rev Nutr 2003; 16: 155-62.
7. Iuliano BA, Frutuoso MFP, Gambardella AMD. Anemia em adolescentes segundo maturação sexual. Rev Nutr 2004; 17: 37-43.
8. Anttila R, Siimes MA. Serum transferrin and ferritin in pubertal boys: relations to body growth, pubertal age, erythropoesis, and iron deficiency. Am J Clin Nutr 1996; 63(2): 179-83.
9. Silva FC, Vitalle MSS, Quaglia EC, Braga JAP, Medeiros EHGR. Proporção de anemia de acordo com o estadiamento puberal, segundo dois critérios diagnósticos. Rev Nutr PUC Campinas 2007; 20(3): 297-306.
10. Vitalle MSS. Perspectivas históricas. In: Braga JAP, Amancio OMS, Vitalle MSS. O ferro e a saúde das populações. São Paulo: Roca; 2006. p. 1-7.
Maria Sylvia de Souza Vitalle
Centro de Atendimento e Apoio ao Adolescente da Disciplina de Especialidades Pediátricas do Departamento de Pediatria da Unifesp EPM
Rua Botucatu 715 4023-62 São Paulo SP