Haemopexin

Hemopexin (Hpx) is a beta globulin that is synthesized in the liver (Walther 2022) and plays a major role in the degradation of intravascular hemoglobin (Müller 2002).

Reference range

The reference range of Hpx is between 50 - 120 mg / dl (Walther 2022).

Task

Free hemoglobin, which is produced during the degradation of erythrocytes and is highly toxic, can be transported to the RES by various proteins and degraded there. A differentiation is made between the so-called

- Acute-phase protein, which corresponds to haptoglobin, and the

- hemopexin, which serves as a transport protein when the free haptoglobin is already depleted (Müller 2002).

However, in massive hemolysis, the transport capacities of haptoglobin are rapidly exhausted (Walther 2022) and free hemoglobin appears in the plasma. The free hemoglobin is converted to hematin derivatives and delivered to the RHS by hemopexin (Herold 2022)

Hemopexin thus steps in as a transport protein, causing the serum concentration of haptoglobin to decrease. Measurements of Hpx can be used to estimate the severity of intravascular hemolysis (Walther 2022).

This results in a graded function of haptoglobin and hemopexin (Herold 2022).

Indications for Hpx determination

- To clarify severely decreased or no longer measurable haptoglobin values

- To assess intravascular hemolysis (Walther 2022)

Evaluation of the measured values

Increased Hpx values are found in e.g.

- hemochromatosis

- Diabetes mellitus

- Malignant melanoma (Walther 2022)

- Gravidity (Gressner 2017)

Decreased Hpx values indicate e.g.

- myolysis

- Myoglobinemia

- Chronic liver diseases such as

- Liver synthesis disorders

- Chronic hepatic porphyria (Walther 2022)

- Liver cirrhosis (Gressner 2017).

- Malnutrition

- Malassimilation

- Massive intravascular hemolysis. In this case, the transport protein haptoglobin is already completely saturated with hemoglobin (Walther 2022).

- Protein loss syndrome

- Malnutrition (Gressner 2022)

Cave: Haptoglobin should always be determined to assess intravascular hemolysis (Walther 2022).

Hpx is mainly synthesized in hepatocytes. Among the serum proteins known to date, it has the highest binding capacity for heme. An Hpx-hem complex is taken up by the hepatocytes and catabolized with a half-life of approx. 8 hours (Gressner 2017).

1. Gressner A M, Gressner O A (2017) Hemopexin. Springer Medicine e.Medpedia DOI: https://www.springermedizin.de/emedpedia/lexikon-der-medizinischen-laboratoriumsdiagnostik/haemopexin?epediaDoi=10.1007%2F978-3-662-49054-9_1383
2. Herold G et al (2022) Internal medicine. Herold Publ. 43
3. Kasper D L, Fauci A S, Hauser S L, Longo D L, Jameson J L, Loscalzo J et al (2015) Harrison's Principles of Internal Medicine. Mc Graw Hill Education
4. Müller K, Müller S (2002) Original examination questions with commentary GK2 clinical chemistry. Georg Thieme Verlag Stuttgart / New York 41
5. Walther R (2022) Hemopexin. Pschyrembel online.