Guamanian neurodegenerative disease: Investigation of the calcium metabolism/heavy meta1 hypothesis

Objective: There is a high prevalence of neurodegenerative disease (parkinsonism, dementia, and motor neuron disease) on the western Pacific island of Guam. We sought evidence in support of the hypothesis that these conditions are triggered by nutritional deficiencies of calcium and magnesium leading to secondary hyperpara-thyroidism that then facilitates the entry of calcium and toxic heavy metals into the brain. Methods: We analyzed indices of calcium metabolism plus blood-serum, urine, nail, and hair heavy metal concentrations in 12 patients with Guamanian neurodegenerative disease and 12 Chamorro control subjects. Results: All 12 patients with Guamanian neurodegenerative disease had normal values for serum total and ionized calcium, 25-hydroxyvitamin D, and 24-hour urine collections for calcium. Eleven of 12 patients had normal serum parathyroid hormone values and alkaline phosphatase levels. No patient had reduced serum phosphorus or magnesium values although a minority of patients and controls had low urinary magnesium concentrations. Median blood-serum and 24–hour urine collections for heavy metals (aluminum, arsenic, cadmium, copper, iron, lead, manganese, mercury, and zinc) were statistically similar in the patient and control groups except for a slight elevation of blood, but not urine, lead in the patient group. Concentrations of heavy metals in hair and nails were similar in the two groups. Conclusions: We could find no evidence in support of abnormalities of calcium metabolism or heavy metal absorption as a major causative factor in the development of neurodegenerative disease on the island of Guam.