Male sex |
Age |
Menopause |
Lifestyle factors including smoking, heavy intake of coffee, and alcohol |
Genetic |
Cystathionine β synthase deficiency (the cause of classic homocystinuria) |
5,10-Methylenetetrahydrofolate reductase deficiency (rare) or thermolability (common) |
Methionine synthase deficiency (rare) |
Nutritional disorders |
Folate deficiency |
Vitamin B12 deficiency |
Vitamin B6 deficiency |
Systemic disease |
Renal failure |
Malignant diseases |
Psoriasis |
Hypothyroidism |
Drugs |
Cholestyramine and colestipol (decrease cobalamin and folate absorption) |
Methotrexate (inhibits dihydrofolate reductase) |
Phenytoin and carbamazepine (antagonise folate) |
Nitrous oxide (inactivates methionine synthase) |
Niacin and theophylline (decrease pyridoxal kinase) |
Androgens (increase muscle mass and serum creatinine) |
Cyclosporin A (decreases renal function) |
Metformin (may decrease cobalamin absorption) |
Fibric acid derivatives (may interfere with renal function) |