What are patterns of insulin secretion by insulinomas?

Updated: May 31, 2020
  • Author: Zonera Ashraf Ali, MBBS; Chief Editor: Neetu Radhakrishnan, MD  more...
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An in vitro study by Henquin et al identified three distinct patterns of insulin secretion by insulinomas, as follows [11] :

  • Group A – Qualitatively normal responses to absence or excess levels of glucose, leucine, diazoxide, tolbutamide, and extracellular calcium chloride (CaCl 2); concentration-dependent effect of glucose, but excessive insulin secretion in both low- and high-glucose conditions
  • Group B – Large insulin responses to 1 mmol/L glucose, resulting in very high basal secretion rates inhibited by diazoxide and restored by tolbutamide but not further augmented by other agents, except for high levels of CaCl
  • Group C – Very low rates of insulin secretion and virtually no response to stimuli (including high CaCl 2 concentration) and inhibitors (with CaCl 2 omission paradoxically stimulatory).

Increased expression of the phosphorylated mechanistic target of rapamycin (p-mTOR) signaling pathway and its downstream serine/threonine kinase p70S6k has been observed in insulinoma tumor specimens. [12] This discovery has led to studies exploring mTOR inhibitors as new therapeutic options.

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