Inorganic phosphate-insulin relationships in normal subjects and in patients with moderate glucose intolerance

The relationship between serum insulin and serum inorganic phosphate levels was investigated in normal subjects (NGT) and in patients with moderate impairment of glucose tolerance (IGT1 with subnormal and IGT2 with excessive insulin secretion) fasting and after oral glucose. Insulin and phosphate fasting levels were similar in all groups. In NGT subjects, a significant correlation between fasting insulin and inorganic phosphate levels are observed. In NGT and in IGT1 subjects, oral glucose administration was followed by a fall in serum phosphate level that was well correlated with the total insulin released. The phosphate fall was severely impaired in IGT2 patients, despite the increased insulin secretion. The plasma ionized calcium levels remain unchanged throughout the OGTT. The present results support the hypothesis that in IGT1 patients a reduced glucose-induced insulin release and in IGT2 patients, a peripheral resistance to insulin action could be the determinant of impaired glucose tolerance.