glucagon

This term refers to a specific biochemical agent that functions as the primary antagonist to insulin. It is characterized by its ability to mobilize energy stores in the liver, specifically converting glycogen into glucose to prevent blood sugar from dropping to dangerous levels. As a chemical substance and hormone, it is treated as an uncountable noun in medical and scientific discourse. It does not have a plural form in standard usage, as it refers to the molecular entity rather than individual countable units.