Human beings need water to live and to ensure the water supply control mechanism exists thirst. Feeling thirsty, man is hydrated and enables control and osmolality and levels of certain ions, proteins and other substances in the body.
To regulate thirst and water intake to the body, the pituitary secretes on its back, the call neurohypophysis, a hormone, antidiuretic hormone (ADH), also called vasopressin (AVP), which is responsible for enhancing the reabsorption renal water level and thereby regulate osmolarity and plasma fluid volume and consequently the pressure and the concentration of various substances in blood.
If for some reason the ADH can not perform its function, the kidney does not recover as much water as it should, with the consequent impact on the body. If this situation occurs can say that the patient suffers from a lack of involvement by operating ADH, what is known as diabetes insipidus.
This involvement is so named not because it has something to do from a causal standpoint with diabetes lack insulin (diabetes mellitus), but by analogy with symptoms of increased thirst, water intake and urine output is occur in both conditions. The absence of urinary glucose loss makes this entity caused by alteration of ADH insipidus receive the qualification, to differentiate diabetes mellitus (sweet).
The absence of antidiuretic hormone (ADH) can be divided into two groups according to the cause that originates:
Diabetes insipidus may be due to the absence of production of DHA level of the neurohypophysis, in whole or in part, or may be due to an alteration of the receptors which detect levels and plasma osmolarity increased with it activates the production of ADH, either because the release threshold is higher than normal, because it would not respond to increases in osmolarity however much it increases.
Central diabetes insipidus is of unknown origin in a 25% -30% of cases and usually appears in adults. By 20% -25% of cases are due to head injuries, 15% -20% to pituitary tumors and to a lesser extent to other entities such as sarcoidosis, histiocytosis, infections, vascular disorders, alcohol or other substances. There is an autosomal dominant familial form that appears in children and an autosomal recessive syndrome, called Wolfram syndrome or syndrome that associates DIDMOAD diabetes insipidus, diabetes mellitus, ocular atrophy and deafness.
Renal diabetes insipidus is due to an alteration in osmolality control level by alteration of renal receptors ADH.The main causes that can cause renal diabetes insipidus are hypercalcemia, hypokalemia and tubular interstitial diseases. There is a familial form of appearance in children linked inheritance X recessively, which can lead to serious dehydration problems, as well as other less common autosomal recessive manner.
The lack of ADH causes increased plasma osmolarity and not enough liquid is retained in the kidney, which the person has a persistent polyuria. This triggers a severe sensation of thirst, so that the patient drinks water constantly, which is known as polydipsia. Nevertheless fails to quench their thirst, so drinking continued for a total of 4-6 liters of water a day, which in extreme cases can reach 16 liters per day.
The onset of symptoms is usually sudden and is accompanied by a little concentrated urine osmolality and low, unlike blood, which will be high.
The diagnosis should be suspected in any person presenting a clinical picture compatible with recent rise and sudden onset of thirst sensation associated with increased water intake and urine output. Should be investigated family history of diabetes insipidus, and the existence of possible causes as head injuries, tumors, infections or other illnesses.
The essential diagnosis is based on the determination of urinary osmolarity, to be diminished below 300 mOsm / kg with an also reduced urinary density (below 1010), and a high plasma osmolarity, 295 mosm above / kg.
To differentiate whether the cause is central or renal ADH given a dose of the patient if it is already with levels in plasma osmolality> 295 mOsm / kg (if not, it will first for about 8 hours without drinking to achieve those levels). If after administration of low osmolarity ADH and urinary rises significantly, the cause is the absence of ADH, that is, be central, whereas if the levels do not change despite the presence of DHA, will cause kidney.
It could determine the levels of DHA in the blood, but not usually done by the high cost of its determination.
When performing a brain MRI will neurohypophysis less brilliant than usual in a normal person, but this imaging is required for diagnosis.
Treatment will differ depending on the central or renal origin of diabetes insipidus.
In diabetes insipidus of central origin, for lack of ADH, the patient will be given the missing hormone, or ADH as desmopressin. In patients with a certain level of production of ADH has been that the administration of chlorpropamide or carbamazepine may stimulate secretion.
In the case of diabetes insipidus treatment will be directed to restricting fluid intake and salt and the use of diuretics such as thiazides. It should monitor blood sodium levels to prevent dehydration or hyponatremia states.
Since most of the time the cause is unknown, there are no preventive measures against the disease.However, it should tell people with these symptoms to come as soon as possible endocrine.
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