[An unusual picture of insulinoma in type-2 diabetes mellitus and morbid obesity].

HISTORY AND CLINICAL FINDINGS

Marked hyperinsulinism was demonstrated in the course of an oral glucose tolerance test (oGTT) in a 63-year-old woman with severe obesity (height 1.59 m, body weight 123 kg, body-mass index 46.4 kg/m2). The diabetic metabolic state, first diagnosed 12 years ago, had been replaced by a low plasma glucose level: she often had attacks of ravenous hunger. A reducing diet of 800 kcal had not been tolerated. She had not had any syncopes. She had continually gained weight since puberty, but her weight had remained relatively constant for the past 5 years during which she had been treated with L-thyroxine for a diffuse goitre (stage II).

INVESTIGATIONS

In the course of an oGTT (75 g glucose) the basal insulin concentration (146 pmol/l) had risen to 1663 pmol/l at 30 min. The basal proinsulin level was 50 times normal (66 pmol/l vs. 1.418 pmol/l), while the initial plasma glucose level had fallen from 4.3 mmol/l to 3.8 mmol/l. Spiral computed tomography of the pancreas showed a 3 x 2.5 cm mass in the region of the tail of the pancreas.

TREATMENT AND COURSE

At laparoscopy a 4 cm tumor was palpated in the region of the pancreatic tail. Left resection of the pancreas was performed. Histopathological examination of the surgical specimen confirmed an insulinoma. A repeat of oGTT 6 months postoperatively demonstrated a markedly diminished insulin level compared with the preoperative results, as well as a diabetic metabolic state.

CONCLUSION

In case of dramatic improvement of diabetes mellitus in an obese patient without drug treatment or weight reduction an insulin-producing tumour should be considered in the differential diagnosis. There may be no typical hypoglycaemic symptoms because of insulin resistance associated with the obesity.