Nephrotoxicity in Humans by the Ultratrace Element Germanium

Acute renal failure (ARF) or renal dysfunction (RD) associated with germanium-induced nephrotoxicity has been reported in 18 patients since 1982. In 2 of these cases the patients died of acute renal and cardiogenic failure. In 17 of 18 cases biopsies showed vacuolar degeneration in renal tubular epithelial cells in the absence of glomerular changes, without proteinuria or hematuria. Accumulated elemental Ge intake in 17 patients over a period of 4 to 36 months ranged between 16 and 328 g, or more than 100 to 2000 times the average estimated dietary intake of Ge for man (1.5 mg/d; range 0.40 to 3.40 mg/d). The biological half-life of Ge is 4.5 days for kidneys, the highest retention level of any organ. The mean concentration of Ge in healthy adult kidneys is 9.0 mg/kg wet weight. In 3 patients studied with Ge-induced RD or ARF, urinary Ge excretion was 9, 15, and 60 ng/mL, compared to > 5 ng/mL in healthy controls, and remained elevated even 12 months after discontinuing supplemental Ge intake. The mechanism for Ge-induced nephrotoxicity remains unknown, although the suspected cause is the inorganic Ge salts, such as germanium dioxide. Sufficient evidence for a role of organogermanium compounds, such as carboxyethyl germanium sesquioxide or citrate-lactate germanate, in Ge-induced nephrotoxicity remains lacking. The recent introduction of over-the-counter Ge "nutritional" supplements in some countries increases the risk of additional cases of Ge-induced nephrotoxicity, especially if appreciable levels of inorganic Ge salts are present and consumed for long periods (> 3 months) at levels above the average daily estimated dietary intake for Ge. Despite promotional claims for over-the-counter Ge preparations as "nutritional" supplements, there is at present no known biological requirement for Ge in any organism; nor has Ge deficiency been demonstrated in any animal. Nephrologists should be alert to the potential of Ge-induced ARF or RD in patients consuming Ge supplements.