Patient's question:
Age 31, several years ago, I also experienced morning hypoglycemia symptoms (sweating profusely, feeling faint, trembling hands; relief could be obtained by eating food or drinking sugary drinks). In the past year, these episodes have become more frequent, but blood sugar tests are normal at other times. Is this an early symptom of diabetes? Or could it be due to other factors or causes?Doctor's answer:
It is advisable to check blood sugar levels during recurrence. Morning hypoglycemia symptoms (sweating profusely, fainting, trembling hands, relieved by eating food or drinking sugary drinks) can be confirmed.Hypoglycemia (Hypoglycemia) is a clinical syndrome caused by various factors or etiologies leading to abnormally low blood glucose levels. Clinically, it primarily presents with manifestations of sympathetic nerve stimulation and central nervous system effects due to hypoglycemia. Brief hypoglycemia can cause brain dysfunction, while prolonged severe hypoglycemia may lead to brain death. Therefore, accurate diagnosis, prevention, and correction of hypoglycemia are important clinical issues to address.
The etiology of hypoglycemia can be categorized into two types based on recurrence time: fasting hypoglycemia and postprandial hypoglycemia.
You have fasting hypoglycemia, which could be a symptom of diabetes.
There are many factors or etiologies that can cause hypoglycemia, with complex mechanisms. Below is a general overview.
### 1. Fasting Hypoglycemia
During prolonged fasting or inability to eat, the external source of glucose is cut off, and the endogenous glycogen reserves are limited (approximately 70–100 g), which are depleted within 10–12 hours. At this point, glucose is primarily maintained through gluconeogenesis. As fasting duration increases, when "supply cannot meet demand," hypoglycemia occurs. People who skip breakfast are more prone to hypoglycemia, affecting learning, work, and labor efficiency.
### 2. Exercise-Induced Hypoglycemia
During prolonged intense exercise or after exercise, due to high energy consumption and rapid oxidation of glucose, if sugar-containing foods are not replenished promptly, hypoglycemia may occur.
### 3. Alcoholic Hypoglycemia
After consuming large amounts of alcohol on an empty stomach, alcohol is oxidized in the liver, excessively reducing NAD+ to NADH, inhibiting the conversion of lactate to pyruvate, and weakening gluconeogenesis. When limited liver glycogen is depleted, hypoglycemia occurs.
### 4. Reactive Hypoglycemia
A sudden discontinuation of high-concentration glucose infusion can cause hypoglycemia. The mechanism may involve the stimulation of excessive insulin secretion by high-concentration glucose infusion, with insulin levels 4–6 times higher than normal. If high-concentration glucose infusion is stopped abruptly, the sustained action of insulin causes blood glucose levels to drop rapidly, leading to hypoglycemia.
### 5. Idiopathic Hypoglycemia
More common in middle-aged women with neurotic tendencies. It is primarily caused by autonomic nervous system dysfunction, excessive vagal nerve stimulation, and excessive insulin secretion, making it a non-organic disease. Recurrence typically occurs 2–3 hours after meals, classified as glucose utilization-induced postprandial hypoglycemia.
### 6. Drug-Induced Hypoglycemia
Mostly occurs during diabetes treatment, often due to excessive use of insulin, oral hypoglycemic drugs (e.g., sulfonylureas), increased activity after medication, or improper dietary coordination.
- Insulin: Lowers blood glucose by increasing glucose utilization and reducing glucose production. Its mechanisms include:
1) Promoting glucose transport into cells in muscle and fat tissues;
2) Accelerating glucose oxidation and fermentation;
3) Promoting glycogen synthesis and storage;
4) Inhibiting glycogen breakdown and gluconeogenesis;
5) Promoting glucose conversion to fat.
- Oral hypoglycemic drugs (e.g., sulfonylureas): Their mechanism involves sulfonylurea drugs binding to receptors on pancreatic β-cell membranes, blocking potassium channels to depolarize the cell membrane, enhancing voltage-dependent calcium channel opening, and increasing intracellular calcium influx. Increased intracellular free calcium triggers exocytosis and promotes insulin release... Even when insulin levels return to pre-treatment levels after long-term use, their hypoglycemic effect persists, possibly due to inhibiting glucagon secretion and increasing insulin sensitivity in target cells; or possibly due to increasing the number and affinity of insulin receptors on target cell membranes. Some drugs, such as salicylates and monoamine oxidase inhibitors, can enhance the hypoglycemic effect of oral hypoglycemic drugs, causing hypoglycemia. Propranolol can also cause hypoglycemia, possibly by reducing glycogen breakdown, leading to hypoglycemia in fasting or insulin-dependent patients.
### 7. Hepatic Hypoglycemia
In cases of severe liver damage, such as advanced cirrhosis, widespread hepatic necrosis, severe viral hepatitis, or severe fatty liver, the liver's ability to store glycogen and perform gluconeogenesis is impaired, leading to ineffective blood glucose regulation and hypoglycemia. Additionally, reduced insulin degradation in the liver also affects blood glucose levels. Hypoglycemia is more likely to occur when carbohydrate intake is insufficient and may alternate with hyperglycemia.
### 8. Pancreatic β-Cell Hyperplastic Hypoglycemia
Due to pancreatic β-cell hyperplasia or tumors, even with low blood glucose levels, insulin is secreted autonomously, reducing glycogen breakdown and increasing glucose utilization, weakening gluconeogenesis. Hypoglycemia occurs during fasting or exercise.
### 9. Postgastrectomy Hypoglycemia
In some patients after digestive tract surgery, such as total or subtotal gastrectomy, blood glucose may drop sharply after meals due to rapid gastric emptying, leading to high glucose stimulation of excessive insulin secretion and hyperinsulinemia, causing hypoglycemia 2 hours post-meal. Additionally, postoperative gastrointestinal hormones (e.g., enteroglucagon) may excessively secrete, stimulating insulin release and promoting hypoglycemia. The oral glucose tolerance curve in these patients shows a rapid rise in blood glucose after sugar intake, followed by a sharp decline. Such patients should eat small, frequent meals and follow a high-protein, low-sugar diet to prevent recurrence.
### 10. Early Diabetic Reactive Hypoglycemia
More common in early-stage type 2 diabetes... Due to delayed insulin secretion by pancreatic β-cells, hyperglycemia occurs; hyperglycemia then stimulates β-cell insulin secretion, leading to hyperinsulinemia, and hypoglycemia appears 4–5 hours after meals. Patients often have a family history of diabetes and are overweight or obese.
### 11. Endocrine Dysfunction Hypoglycemia
When anterior pituitary dysfunction, adrenal cortex dysfunction, or pancreatic α-cell dysfunction occurs, reduced secretion of insulin-antagonistic hormones (e.g., growth hormone, adrenal cortex hormones, and glucagon) can cause hypoglycemia.
### 12. Autoimmune Hypoglycemia
The mechanism is not fully understood but may be related to genetic immune defects. Patients have insulin and insulin receptor autoantibodies. Insulin secreted by pancreatic β-cells binds to autoantibodies, forming complexes. When insulin is released from these complexes, symptomatic hypoglycemia occurs. Additionally, anti-insulin receptor antibodies bind to insulin receptors, blocking insulin's binding to its target receptors and impairing insulin's biological effects (insulin resistance), but occasionally they also bind to insulin receptors, mimicking insulin-like effects and causing severe fasting hypoglycemia... Hypoglycemia and hyperglycemia may alternate in this condition.
### 13. Extrapancreatic Tumor Hypoglycemia
Some extrapancreatic tumors, such as fibrosarcoma, neurofibroma, primary liver cancer, and adrenal cancer, can cause hypoglycemia. The mechanism may involve tumor growth requiring large amounts of glucose and tumor secretion of insulin-like growth factors, increasing glucose utilization and reducing glucose sources. During recurrence, blood glucose levels are very low, and insulin levels are also low (which can distinguish it from insulinomas).
### 14. Neonatal Hypoglycemia
Some newborns are prone to hypoglycemia in the early stages after birth due to inadequate sugar metabolism regulation, insufficient glycogen reserves, excessive consumption, low gluconeogenesis capacity, and insufficient exogenous glucose supply. A few newborns may develop hypoglycemia due to endocrine abnormalities (e.g., hyperinsulinemia) or congenital metabolic defects. According to domestic literature, even in normal full-term newborns, the incidence of hypoglycemia within 72 hours of birth is between 3.3% and 16%, especially in premature infants, small for gestational age infants, and cesarean-section infants. This type of hypoglycemia is usually asymptomatic, but hidden, persistent, and recurrent hypoglycemia can impair brain growth and function in newborns, causing long-term harm. Therefore, prevention is more important than treatment.
### 15. Infant Ketoacidotic Hypoglycemia
Some infants develop ketone bodies in the urine along with low blood glucose. The mechanism may involve multiple factors:
1) Low alanine turnover rate, leading to insufficient gluconeogenesis substrates;
2) Reduced activity of glycogen synthase in the liver, leading to decreased liver glycogen;
3) Long-chain fatty acids unable to enter mitochondria for oxidation, reducing acetyl-CoA levels, which inhibits pyruvate carboxylase and fructose-1,6-bisphosphatase activity, weakening gluconeogenesis. Reduced acetyl-CoA can also activate pyruvate dehydrogenase, leading to increased glucose utilization and further lowering blood glucose. Due to low blood glucose, fat breakdown increases, and ketone body production rises, causing ketoacidotic hypoglycemia.
### 16. Leucine-Sensitive Hypoglycemia
In some infants, consuming foods rich in leucine (e.g., milk, eggs) can cause hypoglycemia due to leucine stimulating excessive insulin release.
### 17. Enzyme Deficiency Hypoglycemia
Certain enzyme congenital defects can cause hypoglycemia. For example:
- Gierke disease (Glycogen Storage Disease type I): Infants lack glucose-6-phosphatase in the liver, preventing glycogen breakdown into free glucose. The generated glucose-6-phosphate cannot cross the liver cell membrane or be converted to free glucose, leading to excessive glycogen accumulation in the liver and hypoglycemia.
- Carnitine palmitoyltransferase deficiency: Long-chain fatty acids cannot enter mitochondria for oxidation in tissues, and the liver cannot oxidize fatty acids into ketones, increasing glucose utilization and lowering blood glucose.
- Medium- or long-chain acyl-CoA dehydrogenase deficiency: Can cause hypoketotic hypoglycemia... The mechanism may involve increased metabolic products such as propionyl-CoA, isovaleryl-CoA, and methylmalonic acid, inhibiting pyruvate carboxylase activity. Methylmalonic acid can also inhibit mitochondrial malate transport, weakening gluconeogenesis, resulting in hypoketotic hypoglycemia.
### 18. Asymptomatic Hypoglycemia
More common in type 1 diabetes patients and pregnant women,。 Some type 1 diabetes patients may experience hypoglycemia during insulin therapy, with recurrent loss of consciousness or seizures in the absence of symptoms, potentially life-threatening. The mechanism is not fully understood but may involve reduced central nervous system recognition, decreased neurotransmitter release, or reduced tissue sensitivity to neurotransmitters. Some women may also develop asymptomatic hypoglycemia during pregnancy, possibly due to the fetus continuously extracting glucose and alanine from the mother, reducing the mother's reliance on glucose for central nervous system energy supply and decreasing glucose demand. Additionally, nocturnal hypoglycemia (pre-dawn hypoglycemia) and Somogyi phenomenon can also cause asymptomatic hypoglycemia. Asymptomatic hypoglycemia poses a greater potential threat to health and should be paid special attention.
Once suspected of hypoglycemia, the patient should immediately consume oral glucose solution or 15 grams of carbohydrates, such as:
- Half a cup of juice
- Half a can of sugar-free soda
- One tablespoon of honey
- One cup of skim milk
- Three whole-grain crackers
- Six sugar cubes
- One to three glucose tablets
- Two to three pieces of candy
After 10–15 minutes, if symptoms persist, repeat the dose. If symptoms subside but more than an hour remains until the next meal, add a portion of a main meal, such as one slice of toast or a small steamed bun. If it occurs at night, additional snacks containing protein and carbohydrates should be consumed.