Elevated Erythrocyte Count (Erythrocytosis/Polycythemia): Causes, Diagnosis, and Relationship with MCV and Liver Enzymes

By SWA

Introduction

Erythrocytes, or red blood cells, are essential for transporting oxygen throughout the body. An increased erythrocyte count—known as erythrocytosis or polycythemia—may be harmless in some cases but can also indicate underlying medical conditions. This condition often presents with symptoms such as headaches, dizziness, or an increased risk of thrombosis, and therefore requires thorough evaluation.

This article explains the possible causes of erythrocytosis in detail, discusses its relationship to other laboratory parameters such as MCV (mean corpuscular volume) and liver enzyme levels, and considers the potential role of medications like hydrocortisone.

1. What is Erythrocytosis?

Erythrocytosis refers to an increased number of red blood cells in the bloodstream. This leads to increased blood viscosity, which can elevate the risk of vascular blockages such as thrombosis, embolism, or stroke.

Normal values:

  • Men: 4.3–5.9 million/µl

  • Women: 4.1–5.1 million/µl

Values above these thresholds are considered abnormal and should be investigated further.

2. Causes of Elevated Erythrocyte Counts

A. Secondary Erythrocytosis

This occurs as a response to chronic oxygen deficiency or hormonal stimulation, without a primary disorder of the bone marrow.

Possible causes include:

  • Chronic lung diseases (e.g., COPD, pulmonary fibrosis)
    → Lead to long-term oxygen deficiency, which stimulates the production of erythropoietin (EPO) and subsequently red blood cell production.

  • Congenital or acquired heart conditions
    → Particularly cyanotic heart disease with right-to-left shunting.

  • High-altitude residence or exposure
    → An adaptive response to lower oxygen levels in the atmosphere.

  • Smoking
    → Leads to carbon monoxide exposure and functional hypoxia, stimulating EPO production.

  • Tumors that produce EPO (e.g., renal cell carcinoma, hepatocellular carcinoma)
    → Stimulate red blood cell production independently of oxygen levels.

  • Use of EPO (e.g., performance-enhancing doping)

B. Absolute Polycythemia (Primary Erythrocytosis)

Polycythemia vera (PV) is a myeloproliferative disorder, where the bone marrow produces red blood cells independently of EPO levels.

Associated symptoms:

  • Itching, especially after warm showers

  • Facial redness

  • Enlarged spleen (splenomegaly)

C. Relative Polycythemia

In this case, the actual number of red blood cells is not increased, but due to fluid loss, they become concentrated in the bloodstream.

Causes:

  • Dehydration (e.g., from sweating, diarrhea, fever)

  • Diuretic use

  • Severe burns

3. Symptoms of Erythrocytosis

  • Headache, dizziness

  • Facial redness (plethora)

  • Visual disturbances

  • Itching (particularly after warm baths/showers)

  • Fatigue, difficulty concentrating

  • Thrombosis, embolism, stroke

4. Diagnosis

Basic diagnostic tests:

  • Complete blood count: RBC count, hemoglobin, hematocrit

  • Reticulocyte count (to differentiate between compensatory and pathological production)

  • Erythropoietin (EPO) level

  • JAK2 mutation test (for suspected PV)

  • Arterial blood gas analysis (to assess hypoxia)

  • Imaging: chest X-ray, echocardiogram, abdominal CT if necessary

5. Relationship with MCV and Liver Enzymes

MCV (Mean Corpuscular Volume)

  • Reflects the average size of red blood cells

  • Normal range: 81–100 fL

Increased MCV (macrocytosis):

  • Vitamin B12 or folate deficiency

  • Liver disease

  • Chronic alcohol use

  • Certain medications (e.g., chemotherapy, anticonvulsants)

  • Myelodysplastic syndromes (MDS)

  • Hypothyroidism

Decreased MCV (microcytosis):

  • Iron deficiency anemia

  • Thalassemia

  • Chronic inflammation

Liver Enzymes

Important liver parameters:

  • Transaminases (AST/GOT, ALT/GPT): indicate liver cell damage

  • GGT and alkaline phosphatase (ALP): suggest cholestasis or bile duct problems

  • Bilirubin: hemoglobin breakdown product processed by the liver

  • Albumin, cholinesterase: reflect liver's synthetic capacity

Elevated liver enzymes may result from:

  • Fatty liver disease (NAFLD), hepatitis, autoimmune liver disease, cirrhosis

  • Drug- or toxin-induced liver injury

  • Alcohol use

Combination: Elevated MCV + Elevated Liver Enzymes

In non-alcoholic patients, this combination may be due to:

  • NAFLD with concurrent vitamin deficiency

  • Myelodysplastic syndromes

  • Hypothyroidism

  • Drug side effects

  • Autoimmune liver diseases

6. Role of Hydrocortisone (20 mg daily)

Hydrocortisone is a glucocorticoid used for adrenal insufficiency, inflammation, and autoimmune conditions.

Potential effects on blood and liver:

  • May stimulate erythropoiesis indirectly
    → By reducing cell breakdown and increasing EPO sensitivity in the bone marrow

  • Liver enzymes:
    Generally not significantly elevated directly by hydrocortisone, but long-term use can promote fatty liver and metabolic changes

  • MCV:
    No direct effect, though indirect effects via nutrient balance or metabolism are possible

Conclusion: Taking 20 mg of hydrocortisone daily is unlikely to be the main cause of elevated MCV or liver enzymes, but could contribute, especially with long-term therapy or in combination with other medications.

7. Treatment

Treatment of erythrocytosis depends on the underlying cause:

  • Secondary erythrocytosis:
    → Address the root condition (e.g., COPD, sleep apnea, tumors)

  • Polycythemia vera:
    → Phlebotomy, low-dose aspirin, cytoreductive therapy if needed

  • Relative polycythemia:
    → Rehydrate and restore fluid balance

Supportive care: Prevent blood clots, modify lifestyle (quit smoking, weight loss)

Summary

An elevated erythrocyte count is a significant lab finding that warrants careful differential diagnosis. Causes range from simple dehydration to serious conditions like polycythemia vera or chronic hypoxia-related disorders.

MCV and liver enzyme levels provide valuable clues about accompanying conditions. An increased MCV with elevated liver enzymes in the absence of alcohol use may point to vitamin deficiencies, liver disease, or medication effects.

Hydrocortisone use is not a common cause of these changes, but may play a secondary role in complex clinical pictures. A comprehensive history, clinical evaluation, targeted blood tests, and imaging are essential to reach an accurate diagnosis and tailor appropriate treatment.

Medical and Scientific References

1. Erythrocytosis / Polycythemia

2. MCV and Anemia Diagnostics

3. Liver Function and Enzymes

4. Hydrocortisone and Its Effects

5. German-language Sources Referenced in Original Input


© 2000-2025 Sieglinde W. Alexander. All writings by Sieglinde W. Alexander have a fife year copy right. Library of Congress Card Number: LCN 00-192742

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