Diabetes insipidus



Diabetes insipidus





A disorder of water metabolism, diabetes insipidus results from a deficiency of circulating vasopressin (also called antidiuretic hormone) or from renal resistance to this hormone. Pituitary diabetes insipidus is caused by deficiency of vasopressin, whereas nephrogenic diabetes insipidus is caused by renal tubular resistance to the action of vasopressin. Diabetes insipidus is characterized by excessive fluid intake and hypotonic polyuria.

The disorder may start in childhood or early adulthood (median age of onset is 21) and is more common in men than in women. Incidence is slightly higher today than in the past.

In uncomplicated diabetes insipidus, the prognosis is good with adequate water replacement, and patients usually lead normal lives.


Causes

Pituitary diabetes insipidus results from intracranial neoplastic or
metastatic lesions, hypophysectomy or other neurosurgery, a skull fracture, or head trauma that damages the neurohypophyseal structures. It can also result from infection, granulomatous disease, and vascular lesions; it may be idiopathic and, rarely, familial.

The hypothalamus synthesizes vasopressin. The posterior pituitary gland (or neurohypophysis) stores vasopressin and releases it into the general circulation, where it causes the kidneys to reabsorb water by making the distal tubules and collecting duct cells water-permeable.

In pituitary diabetes insipidus, the absence of vasopressin allows the filtered water to be excreted in the urine instead of being reabsorbed. In renal diabetes insipidus, the kidney doesn’t respond to vasopressin, which is usually present in high concentrations.


Signs and symptoms

The patient’s history typically shows an abrupt onset of extreme polyuria (usually 4 to 16 L/day of dilute urine, but sometimes as much as 30 L/day). As a result, the patient is extremely thirsty and drinks great quantities of water to compensate for the body’s water loss. This disorder may also result in hourly nocturia.

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Jun 16, 2016 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Diabetes insipidus

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