Haemoglobin and ferritin concentrations in men and women: cross sectional study
BMJ 2002; 325 doi: https://doi.org/10.1136/bmj.325.7356.137 (Published 20 July 2002) Cite this as: BMJ 2002;325:137All rapid responses
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Haemoglobin reference values; should gender be ignored?
EDITOR - The hypothesis stating the differences in mean heamoglobin
levels by genders to be solely due to iron deficiency by D Hugh Rushton
et al 1 and the recent critical paper by Jill Waalen et al2 inspired us
to look at the issue in light of still another population survey. A large
multiphasic screening programme in the years 1966- 1972 consisted of over
50 000 participants. Haemoglobin, serum iron and transferrin measured as
total iron binding capacity (TIBC) were measured ( serum ferritin
determinations were not available at that time) 3,4.
We focused on the population aged 20-49 years, because the prevalence
rate of iron deficiency was particularly evident in this age cohort. Iron
deficiency was defined as high, over 400 µg/l (71.64 µmol/l) TIBC. High
TIBC was the best indicator of scanty bone marrow iron stores4. The mean
heamoglobin level of men (N= 17674) was 154 g/l, the respective figure of
women (N= 13368, pregnant and oestrogen users excluded) 134 g/ l. After
adjusting for TIBC, the mean heamoglobin of men was 153 g/l, that of women
135 g/l. Adjusting for serum iron or transferrin saturation did not
change the results, neither did the exclusion of persons with history of
rheumatoid arthritis, malignancies or uraemia: the mean haemoglobin of men
remained significantly higher than that of women. The effects of sex
hormones are diverse!
There are other features than haemoglobin level, where men and women
differ essentially: coronary heart disease mortality of men is
significantly higher than that of women. However, this seems to be not
due to body iron stores, nor do lower haemoglobin level and iron
deficiency protect women for coronary deaths 5.
Our results are in concordance with Jill Waalen et al, but we
disagree with D Hugh Rushton et al: haemoglobin reference values and
limits for anaemia for men and women should be different.
Heikki Takkunen
assistant professor
Antti Reunanen
assistant professor
National Public Health Institute, Mannerheimintie 166, 00300 Helsinki,
Finland
antti.reunanen@ktl.fi
1. Rushton DH, Dover R, Sainsbury AW, Norris MJ, Gilkes ID. Why
should women have lower reference limits for haemoglobin and ferritin
concentrations than men? BMJ 2001; 322: 1355-1357.
2. Waalen J, Felitti V, Beutler E. Haemoglobin and ferritin
concentrations in men and women: cross sectional study. BMJ 2002; 325:
137.
3. Reunanen A, Aromaa A, Pyörälä K, Punsar S, Maatela J, Knekt P. The
Social Insurance Institution´s coronary heart disease study. Baseline data
and 5-year mortality experience. Acta med Scand Suppl. 1983: 673: 1-120.
4. Takkunen H. Iron deficiency in the Finnish adult population. Scand J
Haematol. Suppl. 1976; 25: 1-91.
5. Reunanen A, Takkunen H, Knekt P, Seppänen R, Aromaa A: Body iron
stores, dietary iron intake and coronary heart disease mortality. J
Intern Med. 1995;238: 223-230.
Competing interests: No competing interests
Androgens? With regard to the discussion between Waalen et
al.(1) and Rushton et al.(2) it is important to note that
very little is known about the stimulation of erythropoiesis
by androgens in the physiological situation. Textbooks on
internal medicine and haematology refer to studies carried
out between 1940 and 1970 that show that haemoglobin values
in castrated rats decrease 5-7 %. Haemoglobin values of
hypogonadal men after hypophysectomy do fall below 130 g/l
only in about half the subjects, and either fail to rise
more than 5 %, or rise to polycythemic values after
treatment with pharmaceutical doses of testosteron. In the
paper bij Gardner et al. cited by Waalen et al. “massive
doses” (the authors’ words) of testosteron resulted in an
increment in red cell and plasma volume whithout a
difference in haemoglobin concentration in 15 men aged
73-82.
No evidence can be found for an effect of androgens on serum
ferritin levels.
Iron? In Waalen’s study a large proportion of the women aged
26-55 have a low iron status and low haemoglobin values
contributing to a low average haemoglobin in this group.
(“Females! How low should we go?”. Rushton DH et al.
electronic response to Waalen et al.(1), August 3, 2002,
bmj.com )
The conclusion is that neither Waalen’s data nor results
from studies on androgen stimulation of erythropoiesis
contradict the hypothesis put forward by Rushton et al. that
the lower limit of the reference values for haemoglobin
should be equal for men and women.
Iron and/or androgens? It is important to make the
distinction and establish correct lower reference limits for
haemoglobin and ferritin for clinical use. Women will
benefit from optimal haemoglobin values and adequate iron
stores.(3) In men and women (iron deficiency) anemia is
often an early symptom of intestinal and haematological
malignancies.
The World Health Organisation (WHO) states that “normal
values (for haemoglobin) should be derived from a
representative sample of healthy persons in whom presence of
nutrient deficiency has been excluded”.(4) While a low
ferritin value has a high predictive value for iron
deficiency, the predictive value of a “normal” ferritin for
exclusion of iron deficiency is far less. Consequently
reference values for haemoglobin and ferritin should be
determined after iron supplementation, preferably up to a
level of low response in an appropriate iron
resorptiontest.(5) Data from studies on iron supplementation
in women demonstrate that the lower limit of normal for
haemoglobin in iron sufficient premenopausal women will be
close to 130 g/l, which happens to be the lower limit of
normal for men as advised by the WHO. (“More on reference
values for haemoglobin in women.” Elion-Gerritzen WE,
electronic response to Rushton DH et al. , Dec. 6, 2001
bmj.com)
Literature
1. Waalen J, Felitti V, Beutler E. Haemoglobin and ferritin
concentrations in men and women: cross sectional study. BMJ
2002;325:137
2. Rushton DH, Dover R, Sainsbury AW, Norris MJ, Gilkes JJH,
Ramsay ID. Why should women have lower reference limits for
haemoglobin and ferritin concentrations than men? BMJ
2001;322:1355-7
3. Elion-Gerritzen WE. Iron deficiency in premenopausal
women and criteria for iron supplementation.(Dutch, abstract
in English) Ned Tijdschr Geneeskd 2001;145:11-3
4. World Health Organization. Technical Report nr. 503.
Nutritional anemia’s. Geneva:WHO;1972
5. Heinrich HC. Falsely low normal values for serum ferritin? Clin Chem
1981;27:786
Competing interests: No competing interests
Sirs,
Analysis of the data presented by Waalen et al[1]
reveals that 38% of women in the San Diego area are
iron deficient using a transferrin saturation level below
20% as an indicator of deficiency.
By focusing on the mean haemoglobin distribution
Waalen et al lost sight of a fundamental part of our
work[2]: Namely, why should women have lower
reference limits for haemoglobin and serum ferritin
concentrations than men? Our explanation for this
discrepancy was that a significant number of women in
the general population are iron deficient. Further, we
proposed that the lower reference limit for serum ferritin
(best predictor of body iron stores[3]) in menstruating
women has been incorrectly set lower than age and
weight matched males. If correct, and the Waalen et al
data[1] suggests we are, the lower female reference
limits for haemoglobin, red blood cell count, and serum
ferritin should be the same as for men.
Males have a higher mean haemoglobin value then
females. This is because they attain higher upper
limits. Thus if the range for men is 135g/L to 175g/L
their mean would be 155g/L while in women using the
same lower value (as we suggest) they would have a
mean of 145g/L (135g/L to 155g/L), which is a 10g/L
difference as Waalen et al found. A similar position is
seen in male primate data from the Zoological Society
of London, compared to their menstruating female
counterparts but unlike humans the lower limit of the
reference range does not significantly differ[4]. To
support their case Waalen et al cite a paper describing
one primate exception (Macaca fascicularis)[5].
However, this study included data from infants,
juveniles, and females half the age of the males and as
such cannot be taken as definitive or representative.
Further data analysis from the Zoological Society of
London for adult male and female macaques (males
109g/L to 161g/L versus 107g/L to 147g/L for
females[4]) supports our previous position: in which we
found no significant sex difference for the lower
haemoglobin reference limit.
Closer inspection of the Waalen et al serum ferritin
data[1] shows a large number of women ‘falling off’ the
lower end of the distribution. The haemoglobin
difference between the sexes was of the range 15 to
20g/L at the lower serum ferritin concentrations. This
cluster is a significant percentage (39%) of those who
had a serum ferritin level below the lowest male value
and as such cannot be ignored.
With reference to the Figure From Waalen et al[1] (Part C), the key feature is the significant number of women with
a serum ferritin below the lowest male value and the
haemoglobin intercept, which is below the accepted
lower limit for males (135g/L). The effect of such a large
number of iron deficient individuals will result in women
having a lower reference limit than men.
In part B of their paper[1], the transferrin saturation data
for 26-55 year olds also shows a significant difference
in the haemoglobin level of between 15 to 25g/L in
menstruating females with a transferrin saturation %
below 20 (the accepted cut off point for iron deficiency),
while in part D (>55 year olds) the difference is around
10g/L. This shows that 38% of menstruating women
(part B) and 29% of post-menopausal women (part D)
can be considered iron deficient. Taking the most
conservative position, the data from part B places 530
women (10% of the sample) as being ‘normal’ (Hb
>120g/L) who had transferrin saturations below 10%
and are undoubtedly iron deficient. Further, using the
male % transferrin saturation data in part B, 18% of
females had transferrin saturation levels below 15%
(the lowest male value) while in the post-menopausal
group (part D) 10% had transferrin saturations <_15. the="the" waalen="waalen" et="et" al="al" study1="study1" demonstrates="demonstrates" presence="presence" of="of" large-scale="large-scale" iron="iron" deficiency="deficiency" in="in" san="san" diego="diego" female="female" caucasian="caucasian" population="population" and="and" if="if" representative="representative" supports="supports" our="our" hypothesis="hypothesis" that="that" haematological="haematological" distributions="distributions" contain="contain" a="a" large="large" proportion="proportion" deficient="deficient" women.="women." p="p"/> The data showing a sex difference with age is more
complex than simply presenting mean values from
uncontrolled populations. Data from aged and weight
matched individuals of known health status, with
absolute ranges, medians, and mean values for
haemoglobin and serum ferritin concentrations would
be needed to address this issue.
We entirely agree that iron deficiency is important in
women’s health. However, Waalen et al do not address
the fact that there is no obvious biological requirement
for females to have a lower serum ferritin or
haemoglobin level than men, nor do they present any
arguments why this should be so. Man appears to
stand out from all other primates in this regard.
Population studies measuring haematological
variables may all be compromised by being sampled
from a population, which is assumed to be normal but
is biologically deficient and the data presented by
Waalen et al[1] actually supports this. Contrary to their
conclusion, our data does withstand scrutiny and we
would argue they supports our hypothesis that iron
deficiency is a significant and detrimental factor in
women presenting with a haemoglobin level below
130g/L. Further, we believe our advocacy to employ the
lower male reference limits for haemoglobin and ferritin
in women, is fully justified. After all in this context men
are non-menstruating women, haematologically
speaking!
References
1) Waalen J, Felitti V & Beutler E. Haemoglobin and
ferritin concentrations in men and women: cross
sectional study. BMJ 2002;325:137
2) Rushton DH, Dover R, Sainsbury AW, Norris MJ,
Gilkes JJH, Ramsay ID. Why should women have lower
reference limits for haemoglobin and ferritin
concentrations than men? BMJ 2001; 322: 1355-1357.
3) Beutler E, Felitti V, Ho NJ, Gelbart T. Relationship of
body iron stores to levels of serum ferritin, serum iron,
unsaturated iron binding capacity and transferrin
saturation in patients with iron storage disease. Acta
Haematol 2002;107 (3):145-9
4) Lynx. Haematological and Biochemical Data Base.
Institute of Zoology, The Zoological Society, London,
UK; January, 2000
5) Giulietti M, La Torre R, Pace M, Iale E, Patella A,
Turillazzi P. Reference blood values of iron metabolism
in cynomolgus macaques. Lab Anim Sci 1991;
41:606-608
Competing interests. None
Competing interests: No competing interests
Reply: Haemoglobin reference values; should gender be ignored?
With great respect assistant professors Takkunen & Reunanen have
missed the point of our work.
Our hypothesis does not relate to “differences in mean haemoglobin
levels by genders to be solely due to iron deficiency”. We high-lighted
the possible adverse affect of iron deficiency in women’s health from
employing lower reference limits for haemoglobin, red blood cell count
and serum ferritin concentrations than in men. The upper reference
limits or mean values are not an issue since we have shown it is
possible for males have a higher mean haemoglobin value then
females because males can attain higher upper limits [1].
If one considers the non-human primate and mammalian data there
are two possible situations:- either humans are unique or they are
abnormal. If we consider the evidence from non-menstruating
mammals:- there is no difference in either the lower or upper
reference ranges, in fact, female lionesses have a higher
haemoglobin level than their male counterpart.
In veterinary medicine there is no sex difference for dogs, cats,
horses, zebras, rats, pig etc, and, we suspect, the duckbill platypus.
One could argue, only primates fed by humans become iron deficient!
In menstruating non-human primates there is no difference in the
lower reference limit for haemoglobin and red blood cell counts
compared to their male counterpart. However, they do have a
significantly lower upper limit, which is almost certainly due to the
effect of menses.
One has to accept therefore that humans are either unique or
abnormal and we favour the later based on the primate and Waalen et
al’s data[2] which, if representative, shows 38% of the San Diego
female population to be iron deficient.
If however, humans are unique what is the supporting evidence? Drs
Takkunen & Reunanen do not address this issue nor do they give any
obvious biological support for why females should have a lower serum
ferritin or haemoglobin level than men. Simply remeasuring deficient
populations does not address the issues we have raised.
Competing interest none.
Reference:
1. Females! How low should we go? BMJ electronic response August 3,
2002
2. Waalen J, Felitti V & Beutler E. Haemoglobin and ferritin
concentrations in men and women: cross sectional study. BMJ
2002;325:13
Competing interests: No competing interests