Reference values of HEPcidin Plus other Iron paramEters in children

Iron plays an essential role in many biochemical processes, particularly in the
production of heme for incorporation into Hb and myoglobin, and Fe-S clusters,
which serve as enzyme cofactors. In iron deficiency, cells lose their capacity
for electron transport and energy metabolism. Clinically, iron de!ciency causes
anemia and may result in neurodevelopment deficits. Conversely, iron excess
leads to complications such as endocrine disorders, liver cirrhosis, and
cardiac dysfunction. Therefore, tight regulation of body iron homeostasis on
both systemic and cellular levels is paramount. These processes comprise
several proteins, most of which have been discovered in the last 20 years.
Defects in these proteins lead to disorders of iron metabolism and heme
synthesis that are characterized by iron overload, iron deficiency, or iron
maldistribution. Cells involved in iron homeostasis are duodenal enterocytes,
hepatocytes, macrophages, and erythroid precursors (Donker AE, 2014).

Hepcidin has emerged as the central regulatory molecule of systemic iron
homeostasis. It is a 25-amino acid peptide hormone that is produced and
secreted predominantly by hepatocytes, circulates in the bloodstream, and is
excreted by the kidneys. By binding to the cellular iron exporter ferroportin
and inducing its internalization and degradation, hepcidin regulates cellular
iron efflux. In this way, the absorption of dietary iron from the intestine and
the release of recycled iron derived from senescent erythrocytes are controlled.
(Galesloot TE, 2011; Kroot JJ, 2011).

Many diseases are associated with alterations in hepcidin concentrations (Kroot
JJ, 2011; Donker AE, 2014).Disorders related to hepcidin deficiency are for
example hereditary hemochromatosis and iron loading anemias due to an
ineffective erythropoiesis like beta-thalassemia. On the other hand, hepcidin
excess plays a critical role in anemia of chronic disease (ACD) and Iron
Refractory Iron Deficiency Anemia (IRIDA), a disease characterized by
resistance to oral iron supplementation due to a defect of the TMPRSS6 gene
encoding matriptase-2. Loss of matriptase-2 activity results in an inability to
reduce hepcidin synthesis during iron deficiency. Accordingly, patients have
increased innate hepcidin concentrations resulting in microcytic hypochromic
anemia with low transferrin saturation percentages.
Therefore, assessment of hepcidin concentrations can serve to exclude or raise
the suspicion for disorders of iron metabolism.

Age and sex stratified reference ranges of hepcidin have been established for
adults (Galesloot TE, 2011, www.hepcidinanalysis.com) and for children aged 0.5
-3 years (Uijterschoot, 2014, thesis). However, for children over 3 years no
reference values are available yet. In this study we aim to obtain reference
values of hepcidin and other iron parameters in children in order to get more
insight in the (patho) physiology of iron metabolism in childhood, and to
contribute to a better diagnosis and treatment of children with either an iron
deficit or an iron surplus.

Aim of the study
* To determine age-and sex-dependent reference values of the iron regulatory
hormone hepcidin.
* To determine age-and sex-dependent reference values of newer parameters to
determine iron deficiency, such as soluble Transferrin Receptor (sTfR),
reticulocyte hemoglobin content (Ret-Hb), and Hb Erythrocytes (RBC Hb)

Patients and methods:

Patients:
Because this study aims to understand the iron metabolism of healthy children,
it is important that the included patients do not suffer from a systemic
underlying disease. Our group therefore consists of basically healthy children.
* who attend the out patient department of the Máxima Medisch Centrum Veldhoven
for minor health problems (eg abdominal pain, cardiac murmur, short stature) or
* who are hospitalized on the pediatric ward of the Máxima Medisch Centrum
Veldhoven for surgery (eg inguinal hernia correction, circumcision, hypospadia
correction, orthopedic surgery) and
* who need a venipunture of infusion drip for diagnostic reasons or for surgery
respectively, in order to avoid extra blood withdrawal.

not applicable