EFFECTS OF HYPOPHOSPHATEMIA ON GLUCOSE-TOLERANCE AND INSULIN-SECRETION

Phosphate is an active participant in energy metabolism, and its defic iency has been associated with changes in insulin sensitivity and gluc ose tolerance. In the present study, we have investigated insulin secr etion and glucose tolerance in individuals with moderate and acute pho sphate deprivation and in patients with chronic hypophosphatemia. The individuals with dietary phosphate deprivation, evidenced by a signifi cant reduction in phosphaturia from 232.3 +/- 37.1 to 56.8 +/- 23.9 mm ol/24 hours, but with normal serum levels of inorganic phosphorus, pre sented circulating glucose and insulin levels similar to those of the pre-dietary period during the oral and intravenous glucose tolerance t ests. In contrast, patients with chronic hypophosphatemia (inorganic p hosphorus < 0.65 mmol/l) presented in hyperinsulinemia during the post absorptive state and during the early and late phases of insulin secre tion after the oral and intravenous glucose stimulus. The physiologica l response of a fall in serum phosphate after glucose administration o bserved in individuals with chronic hypophosphatemia was similar to th at of normal individuals. The presence of hyperinsulinemia both basall y and after glucose stimulation, with normal glycemia, in phosphate-de pleted individuals suggests that this condition is associated with red uced insulin sensitivity. However, severe phosphate deprivation is nec essary for the manifestation of this undesirable association. The devi ation 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 hypophosphate mia in malnourished hypophosphatemic individuals when submitted to par enteral refeeding.