Hypoglycemic symptoms are related to the brain and the sympathetic nervous system. Decreased levels of glucose lead to deficient cerebral glucose availability (ie, neuroglycopenia) that can manifest as confusion, difficulty with concentration, irritability, hallucinations, focal impairments (eg, hemiplegia), and eventually, coma and death. Stimulation of the sympatho-adrenal nervous system leads to sweating, palpitations, tremulousness, anxiety, and hunger.
The adrenergic symptoms often precede the neuroglycopenic symptoms and, thus, provide an early warning system for the patient. Studies have shown that the primary stimulus for the release of catecholamines is the absolute level of plasma glucose. The rate of decrease of glucose is less important. Previous blood sugar levels can influence an individual's response to a particular level of blood sugar. However, one must appreciate that a patient with chronic hypoglycemia can have almost no symptoms.
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JB