<p>Iron in the General Population and Specificities in Older Adults: Metabolism, Causes and Consequences of Decrease or Overload, and Biological Assessment</p>

Abstract

Iron is involved in many types of metabolism, including oxygen transport in hemoglobin. Iron deficiency (ID), ie a decrease in circulating iron, can have severe consequences. We provide an update on iron metabolism and ID, highlighting the particularities in older adults (OAs). There are three iron compartments in the human body: 1) the functional compartment, which consists of heme proteins including hemoglobin, myoglobin and respiratory enzymes; 2) iron reserves (IR), which consist mainly of liver stocks and are stored as ferritin; and 3) transferrin. There are two types of ID. Absolute ID is characterized by a decrease in IR. Its main pathophysiological mechanism is bleeding, which is often digestive and can be due to neoplasia, frequent in OAs. Biological assessment shows low serum ferritin and transferrin saturation (TS) levels. Furthermore, hypochromic microcytic anemia is frequent, and the serum-soluble transferrin receptor (sTfR) level is high. Functional ID, in which IR are high or normal, is due to inflammation, which is also frequent in OAs, particularly in its chronic form. Biological assessments show high serum ferritin, normal or low TS, and normal sTfR levels. Moreover, C-reactive protein is elevated, and there is moderate non-regenerative non-macrocytic anemia. The main characteristics of iron metabolism anomalies in the elderly are the high frequency of ID (20% of ID with anemia in adults ≥85 years) and the severity of its consequences, which include cognitive impairment in case of ID or iron overload and decrease of physical activity in case of ID. In conclusion, causes of ID are frequently intertwined in OAs as a result of the polymorbidity that characterizes them. ID can have dramatic consequences, especially in frail OAs. Thus, measuring the appropriate biological markers prevents errors in the positive diagnosis of ID type, clarifies etiology, and informs treatment-related decision-making.

A importância do ferro no organismo humano: uma revisão integrativa da literatura

“…E esse mineral participa de múltiplos processos metabólicos, e são encontrados como componente de enzimas e outros complexos moleculares. Dentre suas principais funções está o transporte de oxigênio através da hemoglobina, síntese de Ácido desoxirribonucleico (DNA) e transporte de elétrons, por ter capacidade de aceitá-los e doá-los (Manckoundia et al, 2020).…”

Iron Deficiency in Heart Failure: Mechanisms and Pathophysiology

“…It is worth noting that the cumulative amount of oral iron received within the study period exceeds the recommended dosage intravenously to correct ID by more than 15 times [ 8 , 95 ]. Knowing that the main source of iron used by the body is endogenously obtained as a result of scavenging iron from senescent erythrocytes by macrophages [ 67 ], these results may implicate mechanisms other than insufficient dietary iron intake alone as a cause of ID in HF.…”

“…On the other hand, these two definitions of ID might have their own limitations, as serum iron is subjected to circadian variations [ 63 ], and TSAT might be falsely elevated in malnutrition and advanced stages of renal insufficiency [ 50 , 64 , 65 , 66 ]. Recent studies proposed serum soluble transferrin receptor (sTfR) as the most auspicious novel ID-related biomarker since circulating sTfR levels reflect the iron demand of the body in addition to the erythroid proliferation rate quantitatively [ 67 ]. In a similar approach to our bone marrow study, Sierpinski et al found that ID defined as serum sTfR of ≥1.25 mg/L is more accurate in identifying ID when compared to bone marrow staining in clinically stable patients with HF [ 55 ].…”

Serum Trace Elements Concentrations in Patients with Restless Legs Syndrome

“…Except for iron, a possible role of trace metals in the pathogenesis of RLS has scarcely been studied. Indeed, iron, copper, manganese, zinc, selenium, magnesium, and calcium have different biological roles, such as regulation of oxidative stress [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Aluminium, lead, cadmium, arsenic, and mercury damage the peripheral nervous system [ 11 , 15 , 24 ]; hence, peripheral neuropathy is a frequent cause of secondary RLS, being present even in many cases of putative iRLS [ 25 ].…”