What is the interpretation of lab results showing elevated Urine Blood Cells (UBC), low ferritin levels, and elevated Vitamin B12 levels in a patient undergoing testosterone therapy?

Laboratory Interpretation: Iron Deficiency in a Patient on Testosterone Therapy

This patient has iron deficiency anemia, evidenced by a ferritin of 19 μg/L (well below the normal range of 20-200 μg/L for men), and requires immediate iron supplementation and evaluation for the underlying cause of iron loss. 1

Primary Findings

Iron Deficiency (Ferritin 19 μg/L)

• The ferritin level of 19 μg/L is diagnostic of iron deficiency, falling below the normal range for men (20-200 μg/L) established by the American Association for the Study of Liver Diseases 1
• Functional assessment indicates that iron deficiency anemia begins when ferritin reaches 10 μg/L, and this patient is approaching that critical threshold 2
• This low ferritin is inconsistent with iron overload or hemochromatosis, which would show ferritin levels of 150-1000+ μg/L 1

Elevated Hematocrit (51.1%)

• The hematocrit of 51.1% is elevated above the normal range and represents secondary erythrocytosis, likely induced by testosterone therapy 3
• Testosterone therapy increases hematocrit by suppressing hepcidin (by 28%), increasing erythropoietin (by 21%), and upregulating ferroportin and transferrin receptor expression 3
• This creates a paradoxical situation: testosterone-driven erythrocytosis is depleting iron stores as the bone marrow consumes available iron for red blood cell production 3

Elevated Vitamin B12 (1370 pg/mL)

• This elevation is not clinically concerning and does not require intervention
• Elevated B12 can occur with supplementation, liver disease, or malignancy, but in isolation without other concerning features, it is typically benign 4

UBC 352 (Unclear Units/Context)

• If this refers to urinary ferritin or urinary blood cells, elevated levels could indicate hemolysis or renal tubular iron deposition 5
• However, without clear context on what "UBC" represents, this value cannot be definitively interpreted
• If urinary ferritin, levels >170 μg/L suggest chronic hemolysis, which could contribute to iron depletion 5

Clinical Implications and Management

Immediate Actions Required

• Initiate oral iron supplementation (ferrous sulfate 325 mg daily or equivalent) to replenish iron stores 1
• Measure transferrin saturation to confirm iron deficiency and rule out other causes of low ferritin 6, 7
• Evaluate for sources of blood loss: gastrointestinal bleeding (especially in men), hematuria, or occult bleeding 1
• Consider checking complete blood count to assess for microcytic anemia (low MCV, low MCH) which would confirm iron deficiency anemia 2

Testosterone Therapy Considerations

• The testosterone therapy is exacerbating iron depletion by driving erythropoiesis without adequate iron stores 3
• Consider temporarily reducing testosterone dose or extending dosing intervals until iron stores are repleted 3
• Monitor hematocrit closely, as levels >54% increase risk of thrombotic events
• Iron supplementation is essential to continue testosterone therapy safely 3

Monitoring Plan

• Recheck ferritin and transferrin saturation in 8-12 weeks after starting iron supplementation 7
• Target ferritin level should be >50 μg/L to support ongoing erythropoiesis 2
• Monitor hematocrit every 3 months while on testosterone therapy 3
• If ferritin fails to rise despite supplementation, investigate for ongoing blood loss or malabsorption 1

Critical Pitfalls to Avoid

• Do not assume elevated hematocrit indicates adequate iron stores - this patient demonstrates that testosterone-induced erythrocytosis can coexist with severe iron deficiency 3
• Do not continue testosterone at current doses without addressing iron deficiency - this will worsen iron depletion and potentially cause symptomatic anemia 3
• Do not perform HFE genetic testing - the low ferritin excludes hemochromatosis, and such testing would be inappropriate and misleading 1, 6
• Avoid vitamin C supplements >500 mg/day once iron overload is excluded, though this is not relevant in this iron-deficient patient 7