What can we learn from a patient on dialysis for 42 years?

Molybdenum is an essential element in the form of the molybdenum cofactor (Moco). In humans, Moco is required for four enzymes: xanthine oxidase (XO), aldehyde oxidase, sulfite oxidase (SO), and mitochondrial amidoxime-reducing component (mARC). The enzymes are involved in the oxidation of purines to uric acid, metabolism of aromatic aldehydes and heterocyclic compounds, and in the catabolism of sulfur amino acids. Molybdenum cofactor deficiency is a rare autosomal recessive syndrome due to a defective synthesis of Moco, resulting in a deficiency of all the molybdoenzymes. There are no reports on clinical signs of dietary molybdenum deficiency in otherwise healthy humans. Water-soluble molybdate is efficiently absorbed from the digestive tract. The body retention is regulated by urinary excretion. Plasma molybdenum reflects long-term intake and 24-h urinary excretion is related to recent intake. There are no biochemical markers of molybdenum status. Cereal products are the main contributors to molybdenum dietary intake, estimated to 100-170 μg/day in Nordic studies. Little data are available on molybdenum toxicity in humans. A tolerable upper intake level of molybdenum has been based on reproductive toxicity in rats, but the effects have not been reproduced in more recent studies. The U.S. Institute of Medicine (IOM, present National Academy of Sciences, Engineering, and Medicine; NASEM) established a Recommended Dietary Allowance of 45 μg/day in adult men and women in 2001, based on a small study reporting urinary excretion in balance with intake at 22 μg/day. The European Food Safety Authority (EFSA) considered in 2013 the evidence to be insufficient to derive an Average Requirement and a Population Reference Intake, but proposed an Adequate Intake of 65 μg/day for adults.