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Glucose Level Disorders

Q: Which counter-regulatory hormones increase blood glucose levels?

Counter-regulatory hormones include: Glucagon;Epinephrine (adrenaline);Cortisol;Thyroid hormones (iodothyronines);Growth hormone (somatotropin, GH). During fasting, glucagon, GH, cortisol, and epinephrine prevent blood sugar from dropping critically by stimulating glycogenolysis and gluconeogenesis.

Hyperglycaemia et Hypoglycaemia

For medical students2 min readUpdated 2026-10-10

Disorders of blood glucose (glycemia) are pathological shifts where sugar concentration falls outside optimal physiological ranges. They are closely linked to hormonal dysregulation and can lead to critical consequences for the central nervous system.

HyperglycemiaGlucose concentration exceeds 5.5 mmol/L (approx. 100 mg/dL) in the postabsorptive state.

HypoglycemiaCritical drop in blood sugar below 3.3 mmol/L (approx. 60 mg/dL).

NeuroglycopeniaAcute impairment of brain cell energy supply due to glucose deficit.

OverdoseExcessive insulin administration in diabetes mellitus is a frequent cause of refractory hypoglycemia.

Hyperglycemia: Definition and Causes

In biochemistry, hyperglycemia (or hyperglucosemia) refers to a pathological state where blood glucose rises above 5.5 mmol/L. Notably, this threshold is measured in the postabsorptive state (after nutrients from a meal have been absorbed by the gastrointestinal tract).

The primary cause of hyperglycemia lies in impaired hormonal regulation. Endocrine dysregulation prevents the body from properly utilizing glucose, leaving it to circulate in the bloodstream in excess amounts.

Hypoglycemia: A Life-Threatening Emergency

Hypoglycemia (hypoglucosemia) is characterized by a drop in blood glucose below 3.3 mmol/L. Clinically, this condition poses a significantly greater immediate danger to the patient's life than hyperglycemia.

The pathogenesis of this disorder is centered on the phenomenon of neuroglycopenia. Because the brain depends critically on a continuous supply of glucose, a systemic glucose deficit causes acute energy failure in neurons.

If blood sugar is not restored, a cascade of pathological changes leads to severe consequences:

Seizures develop;
Loss of consciousness occurs (deep hypoglycemic coma);
Without intervention, it results in death.

Classification of Hypoglycemic States

Depending on the persistence of the changes, hypoglycemia is divided into two main types:

Transient hypoglycemia. Strictly temporary in nature. In healthy individuals, this state is extremely rare and is usually quickly compensated by the body's internal reserves.
Persistent (pathological) hypoglycemia. Requires medical intervention as it is associated with serious underlying diseases or iatrogenic factors.

Causes of pathological persistent hypoglycemia include:

Insulinoma. A specific neuroendocrine tumor formed by pancreatic $\beta$-cells. Tumor cells secrete the hormone uncontrollably, causing chronic hyperinsulinemia.
Diabetes mellitus. In this context, a critical drop in glucose typically occurs due to insulin overdose, when a patient receives a dose exceeding current metabolic requirements.

Mnemonic

To easily remember the causes of persistent hypoglycemia, think of the "two sources of excess": endogenous (an internal tumor—insulinoma) and exogenous (insulin overdose in diabetes mellitus). Both factors lead to hormone excess and plummeting blood sugar.

Frequently asked questions

Which counter-regulatory hormones increase blood glucose levels?

Counter-regulatory hormones include:

Glucagon;
Epinephrine (adrenaline);
Cortisol;
Thyroid hormones (iodothyronines);
Growth hormone (somatotropin, GH).

During fasting, glucagon, GH, cortisol, and epinephrine prevent blood sugar from dropping critically by stimulating glycogenolysis and gluconeogenesis.

What is the mechanism of hyperglycemia specifically in diabetes mellitus?

Elevated glucose is driven by a decreased insulin-to-glucagon ratio, leading to two main consequences:

Decreased tissue glucose uptake: Counter-regulatory hormone effects are enhanced, and the translocation of GLUT-4 glucose transporters to the membranes of insulin-dependent cells (adipose tissue and skeletal muscle) is impaired. Consequently, glucose is not cleared or stored as glycogen.
Activation of gluconeogenesis: Driven by counter-regulatory hormones (primarily glucagon), hepatic synthesis of glucose from amino acids, glycerol, and lactate is upregulated, further exacerbating hyperglycemia.

Why is hypoglycemia considered more dangerous than hyperglycemia?

Hypoglycemia rapidly induces neuroglycopenia—energy starvation of the brain. This leads to fast and irreversible consequences, including seizures, hypoglycemic coma, and death, whereas chronic hyperglycemia damages the body over a longer timeframe.

What are the diagnostic thresholds for these conditions?

Hyperglycemia is defined by a fasting/postabsorptive glucose level above 5.5 mmol/L, while hypoglycemia is diagnosed when the level drops below 3.3 mmol/L.

What is an insulinoma and how does it affect glycemia?

An insulinoma is a tumor of pancreatic beta cells. It causes pathological hypoglycemia by persistently producing large amounts of insulin, which drives down blood glucose.

Go deeper

Mechanisms of hormonal regulation of carbohydrate metabolism
Biochemical features of the postabsorptive state
Pathogenesis of hypoglycemic coma at the cellular level
Metabolism and functions of pancreatic beta cells