Can molybdenum help with copper excretion?

Molybdenum and Copper Excretion

Yes, molybdenum can help with copper excretion, specifically in the form of tetrathiomolybdate for treating copper overload in Wilson's disease. 1

Mechanism and Clinical Application

Molybdenum as tetrathiomolybdate is used to treat copper overload in Wilson's disease at a dose of 120 mg/day divided into 6 doses of 20 mg each. 1 This represents a formal guideline recommendation from ESPEN (European Society for Clinical Nutrition and Metabolism) published in Clinical Nutrition in 2022. 1

How Molybdenum Affects Copper

The interaction between molybdenum and copper works through several pathways:

• Molybdenum increases fecal copper excretion by forming complexes that prevent copper absorption and enhance biliary excretion of absorbed copper. 2, 3 This is the primary route of copper elimination when using molybdenum therapy.

• High concentrations of molybdenum can induce copper deficiency in animals through competitive mechanisms, demonstrating its potency in reducing copper bioavailability. 1

• Tetrathiomolybdate specifically binds to hepatic copper in proportion to liver copper content, with the copper-molybdenum complexes then being excreted predominantly through feces rather than urine. 4

Important Clinical Distinctions

Wilson's Disease vs. General Copper Toxicity

For Wilson's disease specifically:

• D-penicillamine (250-500 mg/day initially) remains the first-line chelation therapy according to the American Association for the Study of Liver Diseases. 5, 6
• Tetrathiomolybdate serves as an alternative copper-reducing agent when standard chelation is not suitable. 1

For acute copper poisoning:

• Standard chelation with D-penicillamine is preferred as it induces cupruresis (urinary copper excretion), allowing for more precise individual monitoring. 3

Route of Excretion Matters

Molybdenum supplementation does NOT increase urinary copper excretion - it works exclusively by increasing fecal copper elimination. 2, 3 In contrast, penicillamine induces cupruresis, making it more suitable when individual monitoring of copper elimination is needed. 3

Safety Considerations

The upper tolerable limit for molybdenum is 2 mg/day for general supplementation, with toxicity reported at 300-800 mg/day causing hallucinations and seizures. 1 However, therapeutic doses of tetrathiomolybdate (120 mg/day) for Wilson's disease have been used safely under medical supervision. 1

Key Caveats

• Individuals with copper deficiency or inadequate dietary copper are at greater risk of molybdenum toxicity since molybdenum can further deplete copper stores. 7

• Molybdenum absorption is highly efficient (approximately 90%), but most absorbed molybdenum is eliminated through urine, not feces. 1, 2 This contrasts with the copper-molybdenum complexes, which are excreted in feces.

• Regular monitoring of both copper and liver function is essential when using molybdenum therapy for copper overload. 5

Practical Algorithm

For copper overload management:

1. Confirm diagnosis with serum copper, ceruloplasmin, 24-hour urinary copper, and slit-lamp examination for Kayser-Fleischer rings. 5, 6

2. For Wilson's disease: Initiate D-penicillamine as first-line; consider tetrathiomolybdate (120 mg/day in divided doses) as alternative. 1, 6

3. For acute copper poisoning: Use D-penicillamine for better monitoring capability through urinary copper measurement. 3

4. Monitor response through serial copper levels and liver function tests every 6-12 months. 5