Dissociation of renin and aldosterone during dehydration: studies in a case of diabetes insipidus and adipsia

When Thirst Ceases to Exist: A Case Report and Literature Review of Adipsic Diabetes Insipidus Following Coil Embolization of a Ruptured Anterior Communicating Artery Aneurysm

Diabetes insipidus is a condition characterized by inappropriately dilute urine in the setting of serum hyperosmolality. The two predominant subtypes include central (from lack of vasopressin production) and nephrogenic diabetes insipidus (from renal resistance to circulating vasopressin). A common manifestation is the significant pursuant thirst from excessive polyuria. We present a case report and literature review of an infrequent variation of central diabetes insipidus known as adipsic (hypothalamic) diabetes insipidus, characterized by the absence of thirst, secondary to coiling of a ruptured anterior communicating artery aneurysm. Due to the loss of thirst, patients are at a heightened risk for hypernatremia and complications secondary to dehydration. Our patient's course was complicated by recurrent polyuria and hypernatremia, requiring a fixed-dose desmopressin regimen. On follow-up, only partial thirst sensation was restored. We provide a literature review to compare our case report to the scant literature available to broaden the awareness of this infrequent, perilous, manifestation.

Incidence of hyperkalemia during hypertonic saline test for the diagnosis of diabetes insipidus

OBJECTIVE

Hyperkalemia has been reported upon different hypertonic saline infusion protocols. Since hypertonic saline test has recently been validated for the differential diagnosis of diabetes insipidus (DI), we aimed to investigate the course of plasma potassium during the test.

DESIGN

We analyzed data of 90 healthy volunteers and 141 patients with polyuria-polydipsia syndrome (PPS) from two prospective studies evaluating the hypertonic saline test. Our primary outcome was the incidence rate of hypertonic saline-induced hyperkalemia > 5 mmol/L.

METHODS

Participants received a 250 mL bolus of 3% NaCl solution, followed by 0.15 mL/min/kg body weight continuously infused targeting a plasma sodium level of 150 mmol/L. Blood samples and clinical data were collected every 30 min.

RESULTS

Of the 231 participants, 16% (n = 37/231) developed hyperkalemia. The incidence of hyperkalemia was higher in healthy volunteers and in patients with primary polydipsia (25.6% (n = 23/90) and 9.9% (n = 14/141), respectively), and only occurred in 3.4% (n = 2/59) of patients with diabetes insipidus. Hyperkalemia developed mostly at or after 90-min test duration (81.1%, n => 30/37). Predictors of hyperkalemia (OR (95% CI)) were male sex (2.9 (1.2-7.4), P => 0.02), a plasma potassium at baseline > 3.9 mmol/L (5.2 (1.8-17.3), P => 0.004), normonatremia at 30-min test duration (3.2 (1.2-9.5), P => 0.03), and an increase in potassium levels already at 30-min test duration as compared to baseline (4.5 (1.7-12.3), P => 0.003). Hyperkalemia was transient and resolved spontaneously in all cases.

CONCLUSION

The hypertonic saline test can lead to hyperkalemia, especially in patients with primary polydipsia who experience a longer test duration. Monitoring potassium levels in these patients is recommended.

Responses to dehydration in the one-humped camel and effects of blocking the renin-angiotensin system

Our objectives were to compare the levels of circulating electrolytes, hormones, and renal function during 20 days of dehydration in camels versus the level in non-dehydrated camels and to record the effect of blocking angiotensin II AT1 receptors with losartan during dehydration. Dehydration induced significant increments in serum sodium, creatinine, urea, a substantial fall in body weight, and a doubling in plasma arginine vasopressin (AVP) levels. Plasma aldosterone, however, was unaltered compared with time-matched controls. Losartan significantly enhanced the effect of dehydration to reduce body weight and increase serum levels of creatinine and urea, whilst also impairing the rise in plasma AVP and reducing aldosterone levels. We conclude that dehydration in the camel induces substantial increments in serum sodium, creatinine, urea and AVP levels; that aldosterone levels are altered little by dehydration; that blockade of angiotensin II type 1 receptors enhances the dehydration-induced fall in body weight and increase in serum creatinine and urea levels whilst reducing aldosterone and attenuating the rise in plasma AVP.

The renin-aldosterone axis in patients with diabetes insipidus

OBJECTIVE

The objective of the present study was to investigate the renin-aldosterone axis in neurogenic diabetes insipidus in man, in view of the fact that profound abnormalities of this axis have been described in experimental animals with congenital neurogenic diabetes insipidus.

DESIGN AND PATIENTS

Nine patients with neurogenic diabetes insipidus and 11 healthy subjects (controls) were examined under basal conditions, following the standard 8-hour water deprivation test and 1 hour after a subsequent oral rehydration.

MEASUREMENTS

Plasma and urine osmolalities were determined by freezing point depression, plasma sodium and potassium by a method using an ion-selective electrode, plasma AVP, cortisol, aldosterone and plasma renin activity by radioimmunoassay.

RESULTS

Plasma renin activities under basal conditions were significantly higher in patients with diabetes insipidus than in controls (mean +/- SEM 23.4 +/- 6.6 vs 7.8 +/- 1.2 ng/l min). In the diabetes insipidus group, water deprivation caused a twofold increase in plasma renin activities (48 +/- 13.8 ng/l min) while in the control group plasma renin activity levels were not significantly altered (10.2 +/- 1.2 ng/l min). Rehydration did not alter plasma renin activity levels in either group (patients 50.4 +/- 13.2, controls 9.0 +/- 2.4 ng/l min). Plasma aldosterone concentrations under basal conditions did not differ between the two groups (patients 302.4 +/- 37, controls 326.4 +/- 36.5 pmol/l) and did not change in patients with diabetes insipidus after water deprivation or rehydration (307.5 +/- 67.2 and 385.5 +/- 91 pmol/l, respectively). Conversely, controls showed a significant decrease in plasma aldosterone levels after dehydration (201 +/- 27.9 pmol/l), which was attributed to the circardian variation in aldosterone secretion, as shown by a parallel decrease in plasma cortisol levels.

CONCLUSIONS

Patients with diabetes insipidus are hyper-reninaemic, probably because of chronic volume contraction. There is a dissociation between renin and aldosterone in patients with diabetes insipidus under basal conditions, which is exaggerated during water deprivation.

Effect of plasma sodium on aldosterone secretion during angiotensin II stimulation in normal humans

Studies were carried out in normal male subjects (n = 6, age 20-35 years) to determine the interaction of angiotensin II and plasma sodium on aldosterone secretion. These relations were quantified by elevation of plasma sodium with an infusion of 5% sodium chloride (4 ml/kg/30 min i.v.) with measurements of plasma aldosterone, atrial natriuretic factor (ANF), and arginine vasopressin (AVP) over 3 hours. Two hours before sodium chloride infusion, an intravenous infusion of angiotensin II was begun at 0.5 or 5.0 ng/kg/min and continued throughout the study. Plasma potassium was maintained constant by the addition of potassium to the infusate. NaCl/KCl infusion raised plasma sodium 4 meq/l with no decreases of plasma potassium. Plasma aldosterone averaged 7 +/- 1.8 ng/dl before NaCl infusion in subjects infused with 0.5 ng angiotensin II and was not significantly reduced with sodium chloride infusion. Angiotensin II infused at 5 ng/kg/min resulted in average plasma aldosterone levels of 31 +/- 3.6 ng/dl, which sodium chloride infusion decreased to 16.6 +/- 1.3 ng/dl (p less than 0.05) in 60 minutes. Plasma aldosterone remained depressed for the remaining period of study. Plasma ANF increased from 40 to 60 pg/ml with sodium chloride infusion. We conclude that small physiological elevations of plasma sodium concentrations can signal substantial decreases of plasma aldosterone in normal human subjects in situations where plasma angiotensin II is moderately elevated. The precise mechanisms of these responses remain to be determined.

Hypodipsic hypernatremia associated with absence of septum lucidum and olfactory dysfunction

A case of hypodipsic hypernatremia in a 16-month-old Japanese boy is reported. Partial antidiuretic hormone deficiency was present. Computed tomography of the brain revealed absence of septum lucidum. No ophthalmological abnormality could be found. He had hyposmia, which has not been reported previously in association with hypernatremia due to hypodipsia. Forced fluid administration and nasal 1-deamino-8-d-arginine vasopressin treatment could maintain serum electrolyte levels within normal ranges. However, episodes of hypernatremia could not be completely avoided while he was treated with 1-deamino-8-d-arginine vasopressin and ad libitum oral fluid.

Pituitary and hypothalamic dysfunction in a patient with a basal encephalocele

A 31 year old Chinese man was found to have a large basal encephalocele extending into the nasopharynx associated with a cleft palate and chiasmal damage producing visual field defects. He was found to have marked hypothalamic-pituitary dysfunction including deficiencies of growth hormone, thyrotropin, adrenocorticotropic hormone and gonadotropins, diabetes insipidus, adipsia with essential hypernatremia and poikilothermia. This man illustrates the importance of careful assessment of patients with craniofacial anomalies and outlines a simple investigational protocol.

Renin, aldosterone and cortisol during ethanol intoxication and hangover

The effect of ethanol intoxication and hangover on plasma renin activity (PRA), plasma aldosterone (PA) and plasma cortisol (PC) concentrations was studied in 7 healthy supine men in controlled clinical conditions during 18 h beginning at 6 p.m. Large individual variation was observed in the response of PRA, PA and PC to ethanol. Following ethanol, stimulation of PRA was observed at the 14th and the 16th hour (P less than 0.05), of PA at the 4th and the 6th hour (P less than 0.01 and P less than 0.05, respectively) and of PC at the 4th and the 14th hour (P less than 0.01 and P less than 0.05, respectively). Ethanol ingestion suppressed PC during the first hour (P less than 0.02). Water ingestion at 8 a.m. suppressed PA between the 14th and the 16th hour (8-10 a.m.) in control and ethanol experiment (P less than 0.01 and P less than 0.005, respectively). There was a dissociation between PRA and PA, but intra-individually PRA and PA correlated fairly or well. Plasma arginine vasopressin (AVP) and PC were also significantly correlated. The results suggest that changes in PA and PC as well as the dissociation of PRA and PA after ethanol ingestion might be partly related to dehydration and to the increased secretion of hypothalamic and pituitary hormones as well as to sodium and potassium balance. There was a biphasic effect of ethanol, including an inital suppression of PC and a subsequent increase of PC, PRA and PA. Upright posture appears to exaggerate the stimulating effect of ethanol on PRA, PA and PC.