Plasma proinsulin, C-peptide and insulin in diagnostic suppression tests for insulinomas

Turner, R. C.; Hedïng, Lise G.

doi:10.1007/bf01236309

Cited by 72 publications

(23 citation statements)

References 21 publications

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“…Thus, in hyperthyroidism it could be argued that the pancreatic B cell has an increased capacity to secrete proinsulin compared with the euthyroid state, and proinsulin is circulating in high concentrations because of the relatively slow rate of proinsulin removal [15,16]. In contrast to insulin independent diabetes, where the fasting proinsulin concentration is also increased [17], the concentration of proinsulin in thyrotoxicosis is frequently so high that it is in the range which is considered characteristic of patients with insulinomas [14,18].…”

Section: Discussionmentioning

confidence: 99%

Hypersecretion of proinsulin in thyrotoxicosis

Sestoft

Hedïng

1981

Diabetologia

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Summary. The plasma insulin, C-peptide and proinsulin concentrations were investigated in thyrotoxic patients and in normal controls after an overnight fast, during a 36 h fasting period, an intravenous glucose tolerance test and an oral glucose tolerance test. The main finding was a significantly raised concentration of proinsulin in plasma of patients with thyrotoxicosis. After an overnight fast the plasma proinsulin was 0.048 + 0.005 pmol/ml in 15 thyrotoxic patients compared with 0.023 _ 0.012 pmol/ml in 15 euthyroid controls. A twofold rise of plasma proinsulin concentration was also found in thyrotoxic patients during a prolonged fast, and during intravenous and oral glucose tolerance tests. The immunoreactivity of proinsulin in the insulin radioimmunoassay gave rise to slightly elevated concentrations of immunoreactive insulin in thyrotoxic patients in all the conditions investigated. When insulin values were corrected for proinsulin crossreactivity, they were similar in euthyroid controls and thyrotoxic patients. The concentration of plasma Cpeptide was not significantly altered in thyrotoxic patients during intravenous and oral glucose tolerance tests.

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Section: Discussionmentioning

confidence: 99%

Hypersecretion of proinsulin in thyrotoxicosis

Sestoft

Hedïng

1981

Diabetologia

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“…Due to the use of today's specific and sensitive insulin assays, any detectable circulating insulin during neuroglycopenia already reflects inappropriate hyperinsulinemia [12][13][14]. Thus, proinsulin should be determined in any patient during neuroglycopenia [15][16][17][18][19]. Because of these facts endocrinologists and surgeons have become alert to interpret the results of fasting tests in more detail.…”

Section: Introductionmentioning

confidence: 99%

Differentiation of Insulin Secretion Patterns in Insulinoma

2008

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Background In patients with insulinoma, biochemical proof of inappropriately elevated insulin secretion during hypoglycemia is required prior to surgery. Because circulating insulin levels usually vary widely, we have used the combined OGTT-fasting test to define new normative criteria for a retrospective systematic analysis. Methods We retrospectively analyzed insulin concentrations from OGTT-fasting tests of 64 patients with surgically removed insulinomas. In addition, the response to intravenous somatostatin infusions was estimated. Normative criteria were defined to obtain comparable estimates of insulin concentrations: basal, glucose-stimulated maximum, postglucose plateau, and secretory bursts. Results Three types of insulin secretion patterns were identified: (1) the autonomous secretion pattern (type 1, N = 17) with basal and post-OGTT plateau insulin concentrations of approximately 50 mU/L, suppression after OGTT by 41%, virtual absence of distinctive secretory bursts, and resistance to somatostatin-mediated suppression (25 %); (2) the inadequate suppression pattern (type 2, N = 28) with moderately elevated basal and post-OGTT insulin concentrations of approximately 20 mU/L, suppression after OGTT by 73%, absence of secretory bursts, and incomplete somatostatin-induced suppression (56 %); (3) the late-burst secretion pattern (type 3, N = 19) with similar basal and post-OGTT insulin concentrations of 17 mU/L, suppression after OGTT by 76%, true insulin bursts of D 13 ± 11 mU/L (184%), and nearly complete somatostatininduced suppression by 64%. Conclusions By means of a new normative analysis of the combined OGTT-fasting test, three different patterns of insulin secretion can be described in patients with insulinoma: the autonomous secretion type, the inadequate suppression type, and the late-burst secretion type.

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“…Service et al reported that insulinoma patients had C-peptide values at the end of the 72 h fasts greater than or equal to 0.20 nmol/mL (0.60 ng/mL); however, our case does not fulfill that criterion even before conducting the prolonged fasting test [12]. According to the data from the literature, the molar ratio of serum C-peptide to insulin is, in general, decreased in patients with insulinoma than normal subjects, while in our case the ratios were much lower (Table 2) [18][19][20][21][22][23][24][25][26][27][28][29][30][31].…”

Section: Discussionmentioning

confidence: 91%

A Case of Secretin-responsive Insulinoma with Low Serum C-peptide Levels

et al. 2007

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Abstract. Insulinoma is the most common cause of fasting hypoglycemia resulting from autonomous insulin hypersecretion. A 59-year-old woman who had previously had an insulinoma and had undergone a partial pancreatectomy was admitted to our hospital because of recurrence of hypoglycemia after 27 years. She had two unusual endocrinological features: 1) the serum insulin response to intravenous secretin injection was not impaired, and 2) the serum C-peptide levels and ratios of serum C-peptide to insulin were relatively low. Two pancreatic tumors were readily detectable by computed tomography (CT) and magnetic resonance imaging (MRI). The selective arterial calcium injection (SACI) test showed a hyperinsulinemic response by calcium administration to the gastroduodenal artery. A partial pancreatectomy was done and her hypoglycemia disappeared. Histology revealed that the tumors were composed of monotonous, small round cells that were positive for both insulin and cathepsin B. As previous in vitro studies have shown that C-peptide can be metabolized within human insulinoma cells by proteolytic cleavage by cathepsin B, our patient's low serum C-peptide levels might have been caused by degradation of C-peptide by cathepsin B. According to the data from the literature, the molar ratio of serum C-peptide to insulin is generally decreased in patients with insulinoma than normal subjects. This case highlights the need for careful interpretation of C-peptide levels and the intravenous secretin injection test in the diagnosis of insulinoma.

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Plasma proinsulin, C-peptide and insulin in diagnostic suppression tests for insulinomas

Cited by 72 publications

References 21 publications

Hypersecretion of proinsulin in thyrotoxicosis

Hypersecretion of proinsulin in thyrotoxicosis

Differentiation of Insulin Secretion Patterns in Insulinoma

A Case of Secretin-responsive Insulinoma with Low Serum C-peptide Levels

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