The purpose of this study is to determine to what extend a treatment with the iron compounds Iron Isomaltoside 1000 or Ferric Carboxymaltose is leading to hypophosphatemia and to study the potential clinical impact of hypophosphatemia.

Recent studies suggested that intravenous iron preparations for anemia treatment may have adverse effects on phosphorus regulation, as they may induce an increase in the phosphaturic hormone Fibroblast Growth Factor-23 (FGF-23) and a subsequent fall in plasma phosphorus levels.

So far it is unknown if these effects are class- or substance-specific.

This study will address the question whether among female participants with iron deficiency anemia the application of ferric-(III)-derisomaltose and ferric carboxymaltose will cause episodes of hypophosphatemia to same extend. The investigators will additionally compare the effects of the two iron preparations on other parameters of calcium-phosphate metabolism, and decipher potential consequences of hypophosphatemia by analysing cardiac function, immunological parameters and quality of life.

In order to investigate these outcomes, 60 women with iron deficient anemia will be randomised to receive either ferric-(III)-derisomaltose or ferric carboxymaltose.

The monocentric study will be conducted at Saarland University Medical Center. For each participating woman, the study comprises five visits to the study center during a period of five weeks.

Inclusion Criteria:

• written informed consent,
• female,
• gynecological blood losses,
• age ≥ 18 years,
• iron deficiency anemia,
• Hemoglobin < 12,0 g/dl,
• Serum-Ferritin ≤ 100 ng/ml or Serum-Ferritin ≤ 300 ng/ml and Transferrin-saturation ≤ 30 %,
• Intolerance to or inefficacy of an oral iron supplement
• estimated Glomerular Filtration Rate > 15 ml/min/1.73 m²

Exclusion Criteria:

• known hypersensitivity to MonoFer® or FERINJECT®,
• severe, known hypersensitivity to other intravenous iron preparations,
• Plasma Phosphate < 2.5 mg/dl at screening,
• Hemochromatosis,
• Untreated hyperparathyroidism,
• Renal replacement therapy/kidney transplantation,
• Active malignant disease, disease-free survival for less than 5 years,
• Intravenous iron administration within the last 30 days,
• Treatment with erythropoietin or erythropoietin-stimulating agents, transfusion of red blood cells, radiotherapy or chemotherapy within the last 60 days,
• Surgery under anesthetic within the last 10 days,
• Alanine transaminase (ALT) or aspartate transaminase (AST) > 1.5 fold above levels in healthy individuals,
• Acute febrile infections within the last 7 days,
• Chronic inflammatory diseases requiring a systemic antiinflammatory treatment,
• self-reported severe asthma or eczema,
• presence of relative contraindications (any allergy, any immunologic or inflammatory disease, history of atopic allergies), for which a treatment with the medicinal investigational products is not deemed indicated by the investigator,
• pregnancy,
• women of childbearing potential without an effective method of contraception,
• lactating women,
• Present alcohol or drug dependency,
• Patients with a history of a psychological illness or seizures,
• Non-compliance or administration of any investigational drug within 30 days preceding the study start.