Desmopressin Health Dictionary

Diabetes insipidus is a relatively rare condition and must be di?erentiated from DIABETES MELLITUS which is an entirely di?erent disease.

It is characterised by excessive thirst and the passing of large volumes of urine which have a low speci?c gravity and contain no abnormal constituents. It is either due to a lack of the antidiuretic hormone normally produced by the HYPOTHALAMUS and stored in the posterior PITUITARY GLAND, or to a defect in the renal tubules which prevents them from responding to the antidiuretic hormone VASOPRESSIN. When the disorder is due to vasopressin insu?ciency, a primary or secondary tumour in the area of the pituitary stalk is responsible for one-third of cases. In another one-third of cases there is no apparent cause, and such IDIOPATHIC cases are sometimes familial. A further one-third of cases result from a variety of lesions including trauma, basal MENINGITIS and granulomatous lesions in the pituitary-stalk area. When the renal tubules fail to respond to vasopressin this is usually because of a genetic defect transmitted as a sex-linked recessive characteristic, and the disease is called nephrogenic diabetes insipidus. Metabolic abnormalities such as HYPERCALCAEMIA and potassium depletion render the renal tubule less sensitive to vasopressin, and certain drugs such as lithium and tetracycline may have a similar e?ect.

If the disease is due to a de?ciency of vasopressin, treatment should be with the analogue of vasopressin called desmopressin which is more potent than the natural hormone and has less pressor activity. It also has the advantage in that it is absorbed from the nasal mucosa and so does not need to be injected.

Nephrogenic diabetes insipidus cannot be treated with desmopressin. The urine volume can, however, usually be reduced by half by a thiazide diuretic (see THIAZIDES).... diabetes insipidus

Bed-wetting, or the involuntary passage of urine at night. It can occur at all ages but is a particular problem with children and the elderly. In general, paediatricians prefer not to treat enuresis much before the age of six, as it may be a normal phenomenon and usually stops as the child grows older. However, when the condition persists, the child (and parents) need advice. Treatment is by positive reinforcement of bladder control, alarm systems such as the ‘pad and bell’, or ocasionally by drugs such as Desmopressin, which reduces night-time urinary output. Some children have an ‘irritable bladder’ and can be helped by drugs which relieve this. Enuresis is often a result of psychological disturbance, particularly where family relationships are disrupted. In this circumstance medication is unlikely to be e?ective.

Constipation is a common cause of urinary incontinence – and hence bed-wetting – in the elderly and should be treated. Enuresis in the elderly may also be due to organic disease or to mental deterioration and confusion. Appropriate investigation, treatment and nursing should be arranged. (See NOCTURNAL ENURESIS.)

Advice is available from the Enuresis Resource and Information Centre (ERIC) whose weekday helpline is 0117 960 3060. Also www.eric.org.uk... enuresis

An inherited lifelong bleeding disorder similar to haemophilia. People with the condition have a reduced concentration in their blood of a substance called von Willebrand factor, which helps platelets in the blood to plug injured blood vessel walls and forms part of factor VIII (a substance vital to blood coagulation). Symptoms of deficiency of this factor include excessive bleeding from the gums and from cuts and nosebleeds. Women may have heavy menstrual bleeding. In severe cases, bleeding into joints and muscles may occur.

The disease is diagnosed by bloodclotting tests and measurement of blood levels of von Willebrand factor. Bleeding episodes can be prevented or controlled by desmopressin (a substance resembling ADH). Factor or concentrated von Willebrand factor may also be used to treat bleeding.... von willebrand’s disease