Phosphate is an active participant in energy metabolism, and its deficiency has been associated with changes in
insulin sensitivity and
glucose tolerance. In the present study, we have investigated insulin secretion and
glucose tolerance in individuals with moderate and acute
phosphate deprivation and in patients with chronic
hypophosphatemia. The individuals with dietary
phosphate deprivation, evidenced by a significant reduction in
phosphaturia from 232.3 +/- 37.1 to 56.8 +/- 23.9 mmol/24 hours, but with normal serum levels of inorganic
phosphorus, presented circulating
glucose and
insulin levels similar to those of the pre-dietary period during the oral and intravenous
glucose tolerance tests. In contrast, patients with chronic
hypophosphatemia (inorganic
phosphorus < 0.65 mmol/l) presented in
hyperinsulinemia during the postabsorptive state and during the early and late phases of insulin secretion after the oral and intravenous
glucose stimulus. The physiological response of a fall in serum
phosphate after
glucose administration observed in individuals with chronic
hypophosphatemia was similar to that of normal individuals. The presence of
hyperinsulinemia both basally and after
glucose stimulation, with normal glycemia, in
phosphate-depleted individuals suggests that this condition is associated with reduced
insulin sensitivity. However, severe
phosphate deprivation is necessary for the manifestation of this undesirable association. The deviation of
phosphate to the intracellular medium occurring after
glucose administration in hypophosphatemic individuals is similar to that of normal individuals and explains the occurrence of severe
hypophosphatemia in malnourished hypophosphatemic individuals when submitted to parenteral refeeding.