diabetes

diabetes usually refers to the condition known in full as diabetes mellitus. ‘Diabetes’ can be translated, from its Greek derivation, as ‘going through’ — describing the characteristic copious production of urine. ‘Mellitus’ comes from the Latin for honey. There is an excess of sugar (glucose) in the blood and this ‘spills over’ into the urine, bringing an excess of water with it. The cause is either a deficiency of production of the hormone insulin by the pancreas, or defective response of body cells to the action of this hormone, which normally enables glucose and other nutrients to be taken up from the circulating blood. The derangement of metabolism leads to extensive complications. The type of diabetes due to lack of insulin production was fatal before the early 1920s, when treatment with an extract from animal pancreatic tissue was shown to be effective.

The illness with ‘the passing of too much urine’ was known in 1500 bc to the Egyptians; Aretaeus wrote of it in the second century ad as ‘diabetes … a melting down of the flesh and limbs into urine’; Paracelsus described it in the sixteenth century; but it was the English physician Thomas Willis who first reported in 1679 that the urine was ‘so wonderfully sweet’.

A much rarer condition, diabetes insipidus (with copious urine which is not ‘sweet’), is caused by deficiency of antidiuretic hormone (ADH) (also known as vasopressin) from the pituitary gland. ADH normally acts in the kidneys to prevent any greater escape of water in the urine than is necessary to maintain constancy of the salt concentration and volume of the body fluids. When ADH is lacking, due to disease or injury in or near the pituitary gland, the daily output of dilute urine can be 25–30 litres, with extreme thirst to match.

Stuart Judge

See blood sugar; body fluids; insulin; pancreas; pituitary gland.