In principle, the diagnosis of "hypoglycemia" requires the determination of a low level of glucose [<50 mg / dl (<2.78 mmol / l)] during the presence of symptoms of hypoglycemia, as well as the response of symptoms to the introduction of glucose. If the doctor is present with the development of symptoms, you need to take a blood test to determine the level of glucose. If the level of glycemia is within normal limits, hypoglycemia is excluded and no further analysis is required. If the glucose level is very low, the determination of serum insulin, C-peptide, proinsulin, carried out in the same tube, can help differentiate insulin-mediated from insulin-independent, artificial from physiological hypoglycemia and can eliminate the need for further testing. Determining the level of insulin-like growth factor-2 (IGF-2) can help to identify tumors of non-islet cells (secreting IGF-2), a rare cause of hypoglycemia.
However, doctors are rarely present when patients develop symptoms suggestive of hypoglycemia. Home glucometers do not reliably determine hypoglycemia, there are no clear threshold levels of HbA1c, which differentiate prolonged hypoglycemia from normoglycemia. Thus, the need for more expensive diagnostic testing is based on the likelihood of having underlying abnormalities that cause hypoglycemia, with the patient having clinical manifestations and a concomitant disease.
The standard of diagnosis is 72-hour fasting under controlled conditions. Patients drink only non-alcoholic, non-caffeinated beverages, the plasma glucose level is determined at baseline with symptom development and every 4 to 6 hours or 1-2 hours if the glucose level falls below 60 mg / dL (3.3 mmol / L) . Serum insulin, C-peptide and proinsulin should be determined during periods of hypoglycemia for the differential diagnosis of endogenous and exogenous (artificial) hypoglycemia. Fasting stops after 72 hours, if the patient has no symptoms, and the glucose level is within normal limits, or earlier, if the glucose level was below 45 mg / dl (2.5 mmol / l), hypoglycaemia symptoms were observed.
At the end of fasting, the determination of B-hydroxybutyrate (its level should be low with insulin), serum sulfonylureas for the detection of drug-induced hypoglycemia, plasma glucose level after intravenous glucagon injection to detect an increase that is characteristic of insulinoma is performed. There is no data on the sensitivity, specificity, and prognostic value of determining hypoglycemia according to this scheme. There is no specific low glucose value, which would unambiguously establish pathological hypoglycemia during 72-hour fasting; women have lower fasting glucose levels than men, glucose levels can be observed up to 30 mg / dL without developing characteristic symptoms. If symptomatic glycemia was not observed within 72 hours, the patient should be exercising for 30 minutes. If after this hypoglycemia does not develop, the probability of insulinoma is completely excluded, further research is not shown.
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