Exogenous peripherally injected insulin differs from endogenously secreted insulin in a number of aspects, including which of the following?
A) achieves a higher concentration in the periphery than in the liver, contrary to endogenous insulin
B) contains C peptide, which is missing from secreted endogenous insulin
C) is able to bypass insulin resistance observed with endogenous insulin
D) is always extracted from animal sources and therefore is less effective due to sequence differences and anti-insulin antibodies
E) is in the form of proinsulin, whereas endogenous insulin has had C peptide removed

Question

Quizplus · Accepted Answer

Exogenous insulin, when injected peripherally, achieves a higher concentration in the periphery than in the liver, unlike endogenous insulin which is secreted directly into the portal circulation and reaches the liver first. The concentration of exogenous insulin is higher at the site of injection in the periphery, compared to its concentration in the liver. On the other hand, endogenous insulin is higher concentrated in the liver than in the periphery. Insulin is normally secreted by the endocrine pancreas into the portal venous drainage. Thus, it passes through the liver before being seen by the periphery. A certain fraction of insulin is extracted by the liver, so that the concentration of insulin seen by the liver is normally higher than that seen by the periphery. This discrepancy between exogenous and endogenous insulin might contribute to the problems experienced by diabetics such as hypertension and cardiovascular disease.

Exogenous Peripherally Injected Insulin Differs from Endogenously Secreted Insulin in a Number