diabetes mellitus
Meaning of diabetes mellitus: Sugar left circulating rather than delivered into cells, a shortfall that quietly damages small and large blood vessels over years.
Definition of diabetes mellitus
Diabetes mellitus is a group of conditions in which blood glucose stays higher than normal. Glucose is the sugar cells burn for energy, and insulin is the hormone that lets it cross from the blood into cells. The level rises when the pancreas makes too little insulin, when cells respond poorly to the insulin present, or when both occur together.
How do the main types differ?
| Type | What goes wrong | Usual pattern |
|---|---|---|
| Type 1 | The immune system destroys the insulin producing cells of the pancreas | Often begins in childhood or early adulthood; insulin is required from diagnosis |
| Type 2 | Cells resist insulin's effect and the pancreas cannot keep pace with the extra demand | The most common form; develops gradually, often without symptoms at first |
| Gestational | Pregnancy hormones blunt insulin's action | Appears in pregnancy and usually resolves after delivery, leaving a raised later risk of type 2 |
Other forms exist outside these three. Single gene forms run strongly in families and can be mistaken for type 1 or type 2, and high blood sugar also follows damage to the pancreas from disease or surgery, or treatment with steroids.
Why does high glucose damage the body?
Excess glucose attaches to proteins in blood vessel walls and nerves and alters how they behave, and the damage accumulates in proportion to how high the level runs and for how long. In the smallest vessels this shows up in the retina, in the filtering units of the kidney and in the nerves of the feet and hands. In larger arteries it speeds plaque formation, raising the risk of heart attack, stroke and poor circulation in the legs. The two combine in the foot, where reduced sensation hides an injury that reduced blood flow then struggles to heal. Because the early stages produce no symptoms, glucose is tracked by measurement rather than by how a person feels.
How is it different from diabetes insipidus?
Only the name is shared. Both were once identified by the volume of urine passed, and the two Latin words separated them by taste: mellitus for urine sweetened with sugar, insipidus for urine with no flavor at all. Diabetes insipidus has nothing to do with glucose or insulin. It arises when the hormone that tells the kidney to concentrate urine is missing or the kidney stops responding to it, so large volumes of dilute urine are lost. Grouping it with diabetes mellitus is a historical accident of naming.
Used in a sentence
The patient's laboratory results were consistent with a new diagnosis of diabetes mellitus.
Good to know
Diabetes mellitus is distinct from diabetes insipidus, an unrelated condition of water regulation by the kidney, since the two share a name rooted in excessive urination but differ completely in cause and mechanism.
Word origin
Where “diabetes mellitus” comes from
Formed from Greek diabetes, from diabainein, meaning to pass through, an early reference to excessive urination, and Latin mellitus, meaning sweetened with honey, describing the sugar content of the urine.