SERUM LEPTIN AND INSULIN CONCENTRATIONS IN PATIENTS WITH INSULINOMA BEFORE AND AFTER SURGERY

Inferential studies suggest that circulating insulin concentrations po sitively regulate leptin secretion by adipocytes. In humans, however, insulin requires prolonged periods of time, and relatively artificial set-ups before a relationship with leptin can be observed, In the pres ent work, serum leptin concentrations were measured in five patients w ith insulinoma before and one month after surgery and in five control subjects matched by sex and body mass index (BMI). The control subject s presented a mean serum leptin concentration of 6.7+/-1.5 mu/l and a BMI of 24.9 +/- 1.1. The mean serum leptin concentration in patients w ith insulinoma was 11.8 +/- 3.1 mu/l (P < 0.05 vs controls), with a BM I of 26.3 +/- 1.9. After surgery, there was a non-significant reductio n in BMI (25.8 +/- 1.7), and a clear reduction in serum leptin concent ration (5.6 +/- 2.4 mu/l, P < 0.05 vs pre surgical values and no diffe rence vs control subjects). The fasting area under the curve (AUG) of insulin concentration (in mU/1 per 120 min) before surgery was 14421 /- 4981 and after surgery was 1306 +/- 171 (P < 0.05). Before surgery, serum leptin concentrations significantly correlated with BMI (r = 0. 71) and AUC of insulin (r = 0.82), a correlation that was lost after s urgery. In conclusion, serum leptin concentrations are significantly e levated in patients with chronically high insulin levels due to insuli noma. After surgical treatment and normalization of insulin values, le ptin levels return to normal.