Only one sister, who presented with microcephaly and developmental delay, showed signs of dysplasia of the midline structures ie, septum pellucidum and corpus callosum and a large intracranial cyst. In both patients, the vasopressin secretion did not respond to either osmotic or nonosmotic stimuli or was suppressed by a water load. Plasma osmolality values returned to normal after treatment with forced hydration and a vasopressin analogue, desamino-D-arginine vasopressin. These findings indicate a severe defect in the hypothalamic osmoreceptors that control thirst and vasopressin secretion.
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Post a Comment. The most common reasons for these are lesions that affect the thirst center in the brain- craniopharyngiomas, CNS sarcoidosis, germinomas and clipping or rupture aneurysms of the anterior communicating artery of the circle of Willis.
Tight regulation of water balance is accomplished via the thirst mechanism and ADH. Osmoregulation of ADH is mediated by osmoreceptors located in the anteromedial hypothalamus near the neurohypophyseal cell bodies in the supraoptic nucleus.
These osmoreceptors are extremely sensitive to changes in osmotic pressure. For example, an increase in osmolarity of 1 to 2 percent increases ADH secretion. However, ADH secretion alone is not adequate to prevent dehydration, and an intact thirst mechanism is vital for water homeostasis.
Thirst is regulated by hypothalamic osmoreceptors that are sensitive to changes in effective osmotic pressure of body fluids. The osmotic threshold at which the thirst mechanism is activated begins approximately 5—10 mOsm higher than the threshold for ADH release.
These two systems work together to maintain plasma osmolality. With both systems intact, hypernatremia is a rare development, but can occur in patients who have lost their ability to maintain or increase free water intake, for example hospitalized patients and particularly the geriatric population.
There are four variants of adipsic hypernatremia. Type A adipsia is characterized by an upward setting of the osmotic threshold for both thirst and vasopressin release, sometimes called essential hypernatremia. Type B adipsia is characterized by subnormal thirst and vasopressin responses to osmotic stimuli. This is due to partial destruction of the osmoreceptors. Complete destruction of these receptors is classified as type C adipsia, and these patients have complete absence of ADH release and a lack of thirst mechanism.
Type D is an extremely rare form that manifests as only a thirst mechanism failure with an intact ADH production. In all patients with adipsic hypernatremia, a careful neurologic and radiologic evaluation should be performed, looking for a possible treatable disease such as a benign tumor that might restore osmoreceptor function.
Forced drinking to make patients eunatremic is the treatment—that is, scheduled water drinking because there is no thirst mechanism, with some desmopressin if need be—is usually what helps.
Surgical correction of the cause will be helpful in cases where it is possible. Labels: Consult Rounds , natremias.
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Case Report: Severe hypernatremia from psychogenic adipsia.
Adipsic Hypernatremia in Two Sisters
Adipsic Diabetes Insipidus is a rare hypothalamic disorder characterized by a loss of thirst in response to hypernatraemia accompanied by diabetes insipidus. These occur secondary to a congregation of defects in the homeostatic mechanisms of water balance. Initial diagnosis and management was extremely challenging. Long term management required a careful interplay between low dose vasopressin analog treatment and fluids.
Adipsic or essential hypernatremia is a rare hypernatremia caused by a deficiency in thirst regulation and vasopressin release. In , we reported a case in which autoantibodies targeting the sensory circumventricular organs sCVOs caused adipsic hypernatremia without hypothalamic structural lesions demonstrable by magnetic resonance imaging MRI ; sCVOs include the subfornical organ SFO and organum vasculosum of the lamina terminalis OVLT , which are centers for the monitoring of body-fluid conditions and the control of water and salt intakes, and harbor neurons innervating hypothalamic nuclei for vasopressin release. We herein report three newly identified patients 3- to 8-year-old girls on the first visit with similar symptoms. The common features of the patients were extensive hypernatremia without any sensation of thirst and defects in vasopressin response to serum hypertonicity. Despite these features, we could not detect any hypothalamic structural lesions by MRI. Immunohistochemical analyses using the sera of the three patients revealed that antibodies specifically reactive to the mouse SFO were present in the sera of all cases; in one case, the antibodies also reacted with the mouse OVLT. The immunoglobulin Ig fraction of serum obtained from one patient was intravenously injected into wild-type mice to determine whether the mice developed similar symptoms.
Adipsic hypernatremia is a rare disease presenting as persistent hypernatremia with disturbance of thirst regulation and hypothalamic dysfunction. As a result of congenital disease, tumors, or inflammation, most cases are accompanied by structural abnormalities in the hypothalamic-pituitary area. While cases with no hypothalamic-pituitary structural lesion have been reported, their etiology has not been elucidated. Recently, we reported three patients with adipsic hypernatremia whose serum-derived immunoglobulin Ig specifically reacted with mouse subfornical organ SFO tissue. As one of the circumventricular organs CVOs that form a sensory interface between the blood and brain, the SFO is a critical site for generating physiological responses to dehydration and hypernatremia.