Non-sugar diabetes in children

Diabetes insipidus is a disease caused by absolute or relative deficiency of antidiuretic hormone, characterized by polyuria and polydipsia.

Antidiuretic hormone stimulates the reabsorption of water in the collecting ducts of the kidneys and regulates water metabolism in the body.

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Causes of non-sugar diabetes in a child

Diabetes insipidus in children is referred to as its idiopathic form, which can begin at any age in both men and women. Other clinical manifestations of hypothalamic dysfunction and pituitary disorders or later addition of hypothalamic-pituitary disorders indicate that in the idiopathic form, the deficiency of antidiuretic hormone depends on dysfunction of the hypothalamic-pituitary axis. Most likely, there is a congenital biochemical defect of this area, which manifests itself clinically under the influence of various unfavorable environmental factors.

Posttraumatic diabetes insipidus in children can develop as a result of damage localized above the pituitary stalk during a skull injury with a basal skull fracture and rupture of the pituitary stalk or after neurosurgical intervention.

Sometimes permanent polyuria can occur even 1-2 years after the injury. In such cases, it is necessary to reassess the status of patients for the past period with an attempt to identify short periods of clinical manifestation. The latter will make the diagnosis of post-traumatic origin reliable.

It should be emphasized that diabetes insipidus due to accidental head injuries is an extremely rare disease.

The cause of absolute deficiency of antidiuretic hormone (decreased secretion of the hormone) can be damage to the neurohypophysis of any genesis:

• tumors localized above the sella turcica and in the area of the optic nerve chiasm;
• histiocytosis (due to infiltration of the hypothalamus and pituitary gland by histiocytes);
• infections (encephalitis, tuberculosis);
• injuries (fracture of the base of the skull, surgery);
• hereditary forms (autosomal dominant and recessive, linked to the X chromosome);
• Wolfram syndrome (combination with diabetes mellitus, optic nerve atrophy and sensorineural deafness).

In many cases, the exact cause of absolute antidiuretic hormone deficiency cannot be determined, and diabetes insipidus in children is identified as idiopathic. However, before classifying it as idiopathic, multiple re-examinations of the child are necessary, since in half of the patients, morphologically visible changes in the hypothalamus or pituitary gland due to the development of a volumetric process appear only a year after the manifestation of the disease, and in 25% of patients, such changes can be detected after 4 years.

A special form is diabetes insipidus in children, in which resistance to antidiuretic hormone is observed (relative hormone deficiency). The disease is not associated with insufficient secretion of vasopressin or its increased destruction, but occurs due to congenital insensitivity of renal receptors to vasopressin.

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Pathogenesis

Diabetes insipidus in children is associated with insufficient secretion of vasopressin (ADH). In most cases, this is the result of a deficiency of neurosecretory cells in the supraoptic and, to a lesser extent, paraventricular nuclei of the hypothalamus. The depletion of water in the body due to insufficient amounts of antidiuretic hormone causes an increase in plasma osmolarity, which in turn stimulates the mechanisms of thirst development and causes polydipsia. In this way, the balance between the excretion and consumption of water is restored, and the osmolar pressure of the body's fluids is stabilized at a new, slightly elevated level. However, polydipsia is not only a secondary compensatory manifestation of excessive polyuria. Along with this, there is also a dysfunction of the central thirst mechanisms. Thus, according to some authors, the onset of the disease is characterized by a compulsive increase in thirst, which is then accompanied by polyuria with a low relative density of urine.

Diabetes insipidus in children of neurogenic genesis is a disease with pathology of the hypothalamic-neurohypophyseal axis.

Deficiency of antidiuretic hormone leads to polyuria with low relative density of urine, increased plasma osmolality, polydipsia. Other complaints and symptoms are determined by the nature of the primary pathological process.

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Symptoms of non-sugar diabetes in a child

One of the main symptoms of the disease is a significant increase in the excretion of diluted urine. Frequent and profuse urination is observed both during the day and at night. Diuresis in some cases reaches 40 l/day, more often the amount of daily urine fluctuates from 3 to 10 l. The relative density of urine is significantly reduced - on average to 1005, pathological elements and sugar are absent in it. Inability to form concentrated urine and polyuria are usually accompanied by severe thirst both during the day and at night. Deprivation of patients of fluid leads to increased hypovolemia and hyperosmolarity of plasma, resulting in the development of severe clinical manifestations - agitation, fever, hyperpnea, stupor, coma and even possible death (symptoms of dehydration).

Diabetes insipidus in children without pronounced thirst can be observed quite rarely. However, if polyuria is strongly expressed and thirst compensating for the loss of tissue fluid is absent, spontaneous development of the above-described symptoms of dehydration can be expected.

Diabetes insipidus often occurs without clinical manifestations and is detected during laboratory tests (excessive diuresis, low relative density of urine). The clinical picture is usually combined with such neuroendocrine disorders as menstrual irregularities in women, impotence and sexual infantilism in men. Decreased appetite and body weight are quite common, especially with mild thirst. Symptoms of diabetes insipidus can be detected within the framework of panhypopituitarism, cerebral forms of obesity, acromegaly. With such a combination, manifestations are often erased.

Psychopathological manifestations are quite common and are observed in the form of asthenic and anxiety-depressive syndromes.

Diabetes insipidus in children has mildly expressed vegetative disorders. They are more often permanent, although vegetative paroxysms of predominantly sympathoadrenal orientation may also occur. Permanent vegetative disorders are mainly manifested by the absence of sweating, dry skin and mucous membranes and usually accompany the symptoms of diabetes insipidus. In addition to them, lability of blood pressure with some tendency to its increase and a tendency to tachycardia are often detected. Neurological examination reveals only scattered symptoms of diabetes insipidus. Craniograms quite often show a flattened shape of the skull base with small sizes of the sella turcica, which most likely refers to the signs of dysraphic status. EEG disorders are similar to those in other neuro-metabolic-endocrine diseases.

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Diagnostics of non-sugar diabetes in a child

• Polyuria and polydipsia with a relative density of urine of 1001-1005.
• A 3-hour fluid exclusion test: the relative density of urine remains low, plasma osmolality increases. An increase in the relative density of urine with normal plasma osmolality indicates psychogenic polydipsia, which is quite common in early childhood.
• Vasopressin test (5 U subcutaneously): with absolute deficiency of antidiuretic hormone (hypothalamic-pituitary diabetes insipidus), the relative density of urine increases; with resistance to antidiuretic hormone (nephrogenic diabetes insipidus), the relative density of urine remains low.

Instrumental research

Visualization of the hypothalamic-pituitary region - CT, MRI, X-ray examination of the skull.

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Differential diagnosis

Diabetes insipidus in children is differentiated from excessive water consumption or primary polydipsia, which is psychogenic in nature. It is also necessary to remember about polydipsia, which is observed in some cases in patients with schizophrenia.

In psychogenic polydipsia, a dry-eating test helps to reduce diuresis, increase the relative density of urine to the values observed in healthy people (up to 1020), without worsening the patient's condition and symptoms of dehydration. The next stage of differential diagnosis should be to exclude the nephrogenic form of the disease, which is characterized by insensitivity of the renal tubules to vasopressin. The following forms of nephrogenic diabetes insipidus should be kept in mind: acquired form as a consequence of somatic, infectious diseases and intoxications; familial form with a hereditary defect in the development of renal tubules that respond to antidiuretic hormone.

Before diabetes insipidus in children is differentiated from other pathological conditions, a thorough examination of the genitourinary system, kidney function and blood system, and the above tests are necessary.

Treatment of non-sugar diabetes in a child

Elimination of the cause that caused diabetes insipidus in children is the first step in treating symptomatic forms. In this case, surgical treatment of the tumor or radiation therapy are used.

Replacement therapy is carried out with vasopressin preparations. Desmopressin is administered 3 times a day. The dose is selected individually from 100 to 600 mcg per day under the control of the relative density of urine. Patients should avoid situations in which there is difficulty in water supply, since limiting fluid intake can lead to hyperosmolality and dehydration of the body.

Forecast

Provided that children drink freely, diabetes insipidus is not life-threatening. Hormonal replacement therapy with antidiuretic hormone drugs determines a favorable prognosis for life and ability to work. In case of a volumetric formation in the hypothalamic-pituitary region, the prognosis depends on its location and the possibility of treatment.

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