how do beta blockers cause hyperglycemia?!
the exact cellular mechanism
They do not cause hyperglycemia -- infact they can facilitate hypoglycemia! Most of the major adverse effects of beta blocking drugs result from beta-adrenoreceptor blockade -- ie: blocking the effects of epinephrine.
Epinephrine, acting via the beta-adrenergic receptors, has important effects on glucose metabolism. It increases glucose production by stimulating both glycogenolysis and gluconeogenesis from amino acids, glycerol, and pyruvate. It also increases the delivery of these gluconeogenic substrates from the periphery, inhibits glucose utilization by several tissues, and, via the alpha-2-receptors, inhibits insulin secretion.
Beta blockers do not cause Hyperglycemia.If anything they cause HYPOGLYCEMIA by blocking the release of ADRENALIN.Even this action is minimal.Beta blockers mask the symptoms of hypoglycemia because these symptoms are caused by release of adrenalin and if symptoms of hypoglycemia are masked it may be life threatening.So those who use INSULIN injections for diabetes should not use beta blockers except under the strict supervision of a doctor.