The renin-angiotensin-aldosterone system in infancy and childhood in basal conditions and after stimulation

Pre-analytical stability and physiological fluctuations affect plasma steroid hormone outcomes: A real-world study

Since steroids are crucial for diagnosing endocrine disorders, the lack of research on factors that affect hormone levels makes interpreting the results difficult. Our study aims to assess the stability of the pre-analytical procedure and the impact of hormonal physiological fluctuations using real-world data. The datasets were created using 12,418 records from individuals whose steroid hormone measurements were taken in our laboratory between September 2019 and March 2024. 22 steroid hormones in plasma by a well-validated liquid chromatography tandem mass spectrometry method were measured. After normalization transformation, outlier removal, and z-score normalization, generalized additive models were constructed to evaluate preanalytic stability and age, sex, and sample time-dependent hormonal fluctuations. Most hormones exhibit significant variability with age, particularly steroid hormone precursors, sex hormones, and certain corticosteroids such as aldosterone. 18-hydroxycortisol, 18-oxocortisol. Sex hormones varied between males and females. Levels of certain hormones, including cortisol, cortisone, 11-deoxycortisol, 18-hydroxycortisol, 18-oxocortisol, corticosterone, aldosterone, estrone, testosterone, dihydrotestosterone, dehydroepiandrosterone sulfate, 11-ketotestosterone, and 11-hydroxytestosterone, fluctuated with sampling time. Moreover, levels of pregnenolone and progesterone decreased within 1 hour of sampling, with pregnenolone becoming unstable with storage time at 4 degrees after centrifugation, while other hormone levels remained relatively stable for a short period of time without or after centrifugation of the sample. This is the first instance real-world data has been used to assess the pre-analytic stability of plasma hormones and to evaluate the impact of physiological factors on steroid hormones.

Pharmacology of enalapril in children: a review

Enalapril is an angiotensin-converting enzyme (ACE) inhibitor that is used for the treatment of (paediatric) hypertension, heart failure and chronic kidney diseases. Because its disposition, efficacy and safety differs across the paediatric continuum, data from adults cannot be automatically extrapolated to children. This review highlights paediatric enalapril pharmacokinetic data and demonstrates that these are inadequate to support with certainty an age-related effect on enalapril/enalaprilat pharmacokinetics. In addition, our review shows that evidence to support effective and safe prescribing of enalapril in children is limited, especially in young children and heart failure patients; studies in these groups are either absent or show conflicting results. We provide explanations for observed differences between age groups and indications, and describe areas for future research.

Enabling insights into the maturation of the renin-angiotensin-aldosterone system in children-Development of a low-volume LC-MS assay for the simultaneous determination of aldosterone, its precursor, and main metabolite

INTRODUCTION

As part of the renin-angiotensin-aldosterone system (RAAS), aldosterone is key to the pathology of cardiovascular and renal diseases, leading to end-organ damage and cardiovascular death. Because of different aetiology and metabolism, pharmacotherapy in adults shows only limited transferability to children. Comprehensive investigations of humoral parameters, their precursors, and metabolites are necessary to establish a more rational and safe therapy in children. The LENA (Labeling of Enalapril from Neonates up to Adolescents) project aims to generate these missing data in neonates up to adolescents and provide insight into the maturing RAAS.

METHODS

A HRMS (high-resolution mass spectrometry) assay was developed, utilizing blank serum depleted of the endogenous aldosterone, its precursor, 18-hydroxycorticosterone, and its main metabolite, tetrahydroaldosterone. A TOF-MS (time-of-flight-mass spectrometry) scan run in parallel with the simultaneous determination of all three analytes enriches the acquired data. Validation of aldosterone was conducted according to EMA and FDA bioanalytical guidelines.

RESULTS

Using the Sciex TripleTOF 6600, a reliable determination in 50 µL serum was successfully shown. Appropriate calibration ranges from 19.53 pg/mL for aldosterone, 39.06 pg/mL for 18-hydroxycorticosterone, and 78.13 pg/mL for tetrahydroaldosterone to 2500 pg/mL were established to ensure the applicability in diseased paediatric patients. Between-run accuracy and precision for aldosterone ranged between -1.21 and -6.99 % and 2.07 and -10.22 %, respectively, confirming compliance with international guidelines.

CONCLUSION

A simultaneous bioanalytical LC-HRMS assay for the determination of the biomarker aldosterone, its precursor, and main metabolite, utilizing 50 µL serum, was successfully established. This assay facilitates insight into the maturing RAAS from neonates up to adolescents.

Polyhydramnios, Transient Antenatal Bartter's Syndrome, and MAGED2 Mutations

BACKGROUND

Three pregnancies with male offspring in one family were complicated by severe polyhydramnios and prematurity. One fetus died; the other two had transient massive salt-wasting and polyuria reminiscent of antenatal Bartter's syndrome.

METHODS

To uncover the molecular cause of this possibly X-linked disease, we performed whole-exome sequencing of DNA from two members of the index family and targeted gene analysis of other members of this family and of six additional families with affected male fetuses. We also evaluated a series of women with idiopathic polyhydramnios who were pregnant with male fetuses. We performed immunohistochemical analysis, knockdown and overexpression experiments, and protein-protein interaction studies.

RESULTS

We identified a mutation in MAGED2 in each of the 13 infants in our analysis who had transient antenatal Bartter's syndrome. MAGED2 encodes melanoma-associated antigen D2 (MAGE-D2) and maps to the X chromosome. We also identified two different MAGED2 mutations in two families with idiopathic polyhydramnios. Four patients died perinatally, and 11 survived. The initial presentation was more severe than in known types of antenatal Bartter's syndrome, as reflected by an earlier onset of polyhydramnios and labor. All symptoms disappeared spontaneously during follow-up in the infants who survived. We showed that MAGE-D2 affects the expression and function of the sodium chloride cotransporters NKCC2 and NCC (key components of salt reabsorption in the distal renal tubule), possibly through adenylate cyclase and cyclic AMP signaling and a cytoplasmic heat-shock protein.

CONCLUSIONS

We found that MAGED2 mutations caused X-linked polyhydramnios with prematurity and a severe but transient form of antenatal Bartter's syndrome. MAGE-D2 is essential for fetal renal salt reabsorption, amniotic fluid homeostasis, and the maintenance of pregnancy. (Funded by the University of Groningen and others.).

Early urinary angiotensinogen excretion in critically ill neonates

INTRODUCTION

Urinary angiotensinogen is considered a reliable biomarker for intrarenal renin-angiotensin system activity. The aims of this study were to assess the urinary angiotensinogen level during the first day of life and to evaluate its correlation with renal function in critically ill neonates.

METHODS

Urinary angiotensinogen concentration during the first 24 hours of life was measured in 98 critically ill neonates. Neonatal renal function was assessed by urinary levels of cystatin-C, albumin and α1-microglobulin and urinary electrolyte excretion.

RESULTS

Urinary angiotensinogen level decreased with increasing gestational age and body weight in critically ill neonates (P<0.001). After adjustment for gestational age, urinary angiotensinogen level correlated with urinary fractional excretion of sodium and urinary levels of cystatin-C and α1-microglobulin. Multivariate linear regression identified a significant impact of urinary cystatin-C on urinary angiotensinogen level (P<0.001). Furthermore, urinary angiotensinogen was significantly increased in neonates with a urinary cystatin-C-to-creatinine ratio ⩾2500 ng/mg, which was the optimal cut-off value to predict acute kidney injury in our previous study.

CONCLUSIONS

The urinary angiotensinogen level correlates with the overall maturity of renal function during the early postnatal period in critically ill neonates and an increased urinary angiotensinogen level might reflect renal injury in immature neonates.

Ontogeny of angiotensin type 2 and type 1 receptor expression in mice

In the current experiment, we determined angiotensin type 2 receptor (AT2R) and angiotensin type 1 receptor (AT1R) protein expression by western blot analysis in developing normal mice. The results indicate that: (1) in all detected brain regions and in the spinal cord, adult mice exhibited significantly higher AT2R expression and lower AT1R expression in total protein extracts compared to fetuses and neonates; (2) other major organs, including heart, lung, liver and kidney, exhibited the same expression pattern as the brain and spinal cord; (3) reciprocal changes in AT2R and AT1R expression were found in the total protein extracts from the brainstems of mice from one-day prenatal to six weeks of age, and there was a negative correlation between AT2R and AT1R protein expression; (4) in both membrane and cytosolic fractions from the brainstem, adult mice exhibited higher AT2R and lower AT1R expression than did fetuses and neonates; and (5) in the brainstem, there were no significant differences in AT2R and AT1R messenger RNA (mRNA) levels among fetal, neonatal and adult mice. The above results reconfirmed our previous finding in rats that adult animals have higher AT2R and lower AT1R expression compared to fetuses and neonates. These data imply an involvement of AT1R in fetal development and of AT2R in adult function.

Apparent mineralocorticoid excess: time of manifestation and complications despite treatment

Here we describe the case of a patient followed from birth because of a positive family history for apparent mineralocorticoid excess (AME) in an older brother. The patient, a girl, had normal serum electrolyte and blood pressure measurements in the first months after birth. Not until the age of 11 months did she develop anorexia and failure to thrive in combination with hypertension, hypokalemia, and metabolic alkalosis, which are consistent with the diagnosis of AME. This diagnosis was confirmed by mutation analysis of the HSD11B2 gene (C1228T). Treatment with amiloride and furosemide electrolyte disturbances normalized her blood pressure. At the age of 19 years she unexpectedly suffered a stroke. Additional investigations revealed no accepted risk factor for stroke. We discuss the possible underlying mechanisms for the delayed manifestation of hypertension and electrolyte disturbances in AME, propose an additional explanation for the stroke in this patient, and advise treatment with a mineralocorticoid receptor antagonist to reduce stroke risk in patients with AME.

Physiological partial aldosterone resistance in human newborns

In the neonatal period, the human kidney is characterized by an impaired ability to regulate water and sodium homeostasis, resembling partial aldosterone resistance. The aim of our study was to assess this hormonal insensitivity in newborn infants and to determine its relationship with neonatal sodium handling. We conducted a prospective study in 48 healthy newborns and their mothers. Aldosterone, renin, and electrolyte concentrations were measured in umbilical cords and in maternal plasma. Urinary aldosterone concentrations and sodium excretion were determined at urination within 24 h after birth. A significant difference was observed between aldosterone and renin levels in newborn infants compared with their mothers (817 +/- 73 versus 575 +/- 55 pg/mL and 79 +/- 10 versus 15 +/- 2 pg/mL, respectively, p < 0.001). This hyperactivation of the renin-angiotensin-aldosterone system was associated with hyponatremia and hyperkalemia in the newborn infants, and high urinary sodium loss, consistent with a partial aldosterone resistance at birth. Unlike plasma aldosterone, urinary aldosterone concentration was found highly correlated with plasma potassium concentrations, thus representing the best index for accurate evaluation of mineralocorticoid sensitivity. Our study represents a comprehensive characterization of the renin-aldosterone axis in newborn infants and provides evidence for physiologic partial aldosterone resistance in the neonatal period.

Diagnosis of diseases of steroid hormone production, metabolism and action

Biochemical tests have been the basis for investigations of disorders affecting steroid hormones. In recent years it has been possible however to study the genes that determine functional enzymes, cofactors, receptors, transcription factors and signaling systems that are involved in the process. Analyses of mutations are available as a diagnostic service for only a few of these genes although research laboratories may be able to provide a service. Both biochemical and genetic research have brought to light new disorders. Some genes for transcription factors involved in the development of the endocrine organs have also been identified and patients with defects in these processes have been found. This paper will review general aspects of adrenal disorders with emphasis on clinical and laboratory findings. As with all endocrine investigations there are few single measurements that provide a definitive answer to a diagnosis. Timing of samples in relation to age, gender and time of day needs to be considered.

The plasma angiotensin II level increases in very low-birth weight infants with neonatal chronic lung disease

BACKGROUND

Angiotensin II (AII) has been reported to play an important role in organ fibrosis, and a local renin-angiotensin-system (RAS) has been demonstrated in the lungs. However, the relationship of the RAS to chronic lung disease of the newborn (CLD) remains obscure.

OBJECTIVE

To investigate the plasma AII levels throughout the neonatal period in very low-birth weight (VLBW) infants and examine the possible factors that might affect the AII levels.

STUDY DESIGN

The study includes 20 VLBW infants. Blood samples were collected on days 0, 7, 21 and 35 and plasma AII levels were assayed using an enzyme immunoassay. The data were analyzed by a multiple linear regression analysis with the plasma AII level as the dependent variable and significant factors determined based on a univariate analysis as independent variables.

RESULTS

The geometric mean of the plasma AII concentrations on days 0, 7, 21 and 35 was 51 pg/mL, 86 pg/mL, 132 pg/mL, and 50 pg/mL, respectively. On day 21, only CLD (p<0.01) had a highly significant association with the plasma AII level. On day 35, birth weight (p<0.05) and CLD (p<0.01) had a highly significant association with the plasma AII level. This analysis confirmed CLD to be the most significant factor associated with plasma AII level on days 21 and 35.

CONCLUSION

These findings suggest that higher levels of plasma AII in VLBW infants appear to be related to the development of CLD.

Plasma angiotensin II concentrations in the early neonatal period

BACKGROUND

There have been only a few reports on the renin-angiotensin system in low birthweight infants; in particular, plasma angiotensin II concentrations have not been studied.

AIM

To investigate plasma angiotensin II concentrations in early neonatal infants including low birthweight infants.

METHODS

Forty six patients were studied, of whom 14 weighed not less than 2500 g (normal birth weight), 16 weighed less than 2500 g but not less than 1500 g (moderately low birth weight), and 16 weighed less than 1500 g (very low birth weight). Blood samples were collected twice, on day 0 and day 7. Angiotensin II concentration was assayed using an enzyme immunoassay kit with a microplate.

RESULTS

Geometric means of angiotensin II concentrations on day 7 were 19 pg/ml in the normal birthweight group, 28 pg/ml in the moderately low birthweight group, and 76 pg/ml in the very low birthweight group. The concentrations on day 7 in the very low birthweight group were significantly higher than those in the normal birthweight and moderately low birthweight groups (p = 0.005, p = 0.031). There were significant correlations between angiotensin II concentration on day 7 and gestational age (r(s) = -0.4, p = 0.007) and birth weight (r(s) = -0.36, p = 0.016).

CONCLUSIONS

Specific physiological conditions associated with a very low birth weight are thought to be responsible for the increased concentration of angiotensin II on day 7. It is necessary to measure angiotensin II concentration for a longer period after birth and study the factors that could influence it.

Renal Interlobar Artery Parameters with Duplex Doppler Sonography and Correlations with Age, Plasma Renin, and Aldosterone Levels in Healthy Children

OBJECTIVE

The objectives of this study were to compare and make correlations between age and Doppler parameters of the interlobar arteries, including synchronously obtained plasma renin and aldosterone levels and to obtain new normative data regarding acceleration time in healthy children from neonates to 16 years.

SUBJECTS AND METHODS

One hundred sixty-nine healthy children (72 girls and 97 boys) were classified into four groups: group 1 (< 1 year; n = 34), group 2 (range, 1-6 years; n = 48), group 3 (range, 6-12 years; n = 50), and group 4 (range, 12-16 years; n = 37). Blood samples from the renin and aldosterone were collected in the morning after bed rest and fasting. The resistive index (RI), pulsatility index (PI), and the acceleration time of the renal interlobar arteries with duplex Doppler sonography, including both kidney longitudinal lengths with grayscale sonography, were evaluated. One-way analysis of variance with the least significant difference post-hoc test and Pearson's correlation test were used to compare the differences between groups and to make correlations, respectively. An independent-sample t test was used to evaluate the differences between all parameters based on sex and to compare the left and right kidney longitudinal lengths in each group.

RESULTS

The RI, PI, and acceleration time were statistically significant in between-group comparisons. Only in group 4 was acceleration time not statistically significant compared with groups 2 and 3. Plasma renin levels were significantly higher in group 1 compared with groups 2 (p < 0.03) and 4 (p < 0.0001); in group 2 compared with group 4 (p < 0.05); and in group 3 compared with group 4 (p < 0.01). The plasma aldosterone levels were significantly higher only in group 1 compared with groups 2 (p < 0.001), 3 (p < 0.008), and 4 (p < 0.0001). The RI correlated linearly with the PI, plasma renin levels, and aldosterone levels and correlated inversely with acceleration time. Age had a negative correlation with the RI, PI, plasma renin levels, and aldosterone levels and correlated positively with acceleration time. There were no statistically significant differences between all parameters based on sex and no significant difference found between the right and left kidney longitudinal lengths in each group.

CONCLUSION

The RI in children up to 54 months old is higher than in adults. Therefore, the adult mean renal RI criterion of 0.70 should be applicable to children 54 months old and older. We showed that the age dependency of the RI was directly related to that of plasma renin and aldosterone levels in healthy children in whom Doppler parameters and blood analysis were evaluated synchronously.

Serum cortisol and cortisone levels in newborns with congenital adrenal hyperplasia before the start of therapy

Sodium loss in infants with salt wasting (SW) congenital adrenal hyperplasia (CAH) does usually not occur within the first week of life. We hypothesized that sufficient mineralocorticoid activity might by temporarily maintained by still appropriate concentrations of cortisol. Plasma samples were obtained from 15 infants with SW-CAH before the onset of sodium loss, 17 patients with simple virilizing (SV)-CAH and 28 healthy infants under 14 days of age. Plasma aldosterone concentrations were significantly lower in SW-CAH infants than in SV-CAH patients and in healthy neonates. Plasma cortisol levels and cortisol/cortisone (F/E) ratios in SW-CAH patients were almost the same as in the SV-CAH and control group. While declining plasma aldosterone levels precede the onset of SW in CAH patients, plasma cortisol concentrations are kept normal in SW-CAH infants, temporarily maintaining sufficient mineralocorticoid activity.

Haemodynamic and renal effects of dopexamine after cardiac surgery in children

Dopexamine hydrochloride, a synthetic dopamine analog with predominantly beta and delta agonist properties, has been shown to improve cardiac performance and renal function in adults with heart failure. This study was designed to investigate the haemodynamic and renal effects of dopexamine in children after cardiac surgery. Seven children were selected in whom a need for postoperative vasodilation after cardiac surgery was anticipated. Haemodynamics and renal function were determined under baseline conditions and during a continuous infusion of dopexamine at 2 and 6 micrograms.kg-1.min-1 for 90 minutes, the sequence being randomized for the initial dose. Cardiac output was measured by thermodilution and glomerular filtration rate (GFR) and renal plasma flow (RPF) by the clearances of inulin and para-aminohippurate respectively. Dopexamine induced a dose-related increase in cardiac index (CI) expressed as mean (SD) from 3.5 (0.7) to 3.9 (0.76) and 4.5 (0.8) l.min.-1m-2 (both P < 0.05), and in heart rate (HR) from 107 (17) to 122 (17) and 136 (17) beats.min-1 (P < 0.05). Stroke volume index (SVI) and mean systemic pressure were unchanged, but pulmonary wedge pressure decreased from 14 (3) to 11 (4) and 12 (3) mmHg (both P < 0.05). Systemic vascular resistances (SVR) decreased from 24 (7) to 20 (5) mmHg.l-1.min-1.m-2 (P < 0.05), with dopexamine 6 micrograms.kg-1.min-1. Renal blood flow (RBF) increased from 319 (113) to 441 (230) and 410 (138) ml.min-1.m-2 (both P < 0.05), GFR from 115 (32) to 142 (34) and 146 (29) ml.min-1.1.73m-2 (both P < 0.05), urine output and fractional excretion of sodium respectively from 3.12 (2) to 7.16 (8) and 7.21 (6) ml.kg-1 (both P < 0.05) and from 2.24 (1) to 4.25 (3.4) (P < 0.05) and 3.15 (3.1)% (n.s.). The fraction of CI delivered to the kidneys, the fraction of RBF filtered in the kidneys, plasma renin activity and aldosterone levels remained unchanged. In children after cardiac surgery, dopexamine increases CI at the expense of a concomitant increase in heart rate and demonstrates few selective vascular systemic or intrinsic renal actions.

Developmental renal physiology of the low birth weight pre-term newborn

PURPOSE

The remarkable growth of the kidney and the rapid changes in renal function in the second half of gestation and early postnatal period are discussed.

MATERIALS AND METHODS

Adaptation to the extrauterine environment involves immediate postnatal natriuresis that is prolonged in the pre-term neonate, followed by the sodium retention necessary for growth. Glomerular filtration rate increases throughout the postnatal period, and it is modulated by the renin-angiotensin system and prostaglandins. Because of this, the fetus and neonate are particularly susceptible to renal injury following the administration of angiotensin converting enzyme inhibitors or nonsteroidal anti-inflammatory drugs. Renal tubular function in the neonate is characterized by reduced renal concentration and acidification ability, which can be further compromised by obstructive uropathy. Urine calcium excretion is high in the neonate, which can be aggravated by calciuric drugs, such as furosemide and glucocorticoids.

RESULTS

Reduced renal mass results in compensatory renal growth even in the fetus, a response that could prove maladaptive later in life through excessive glomerular hyperfiltration and progressive interstitial fibrosis.

CONCLUSIONS

These factors underscore the importance of attempting to maximize functional renal mass in the neonate or infant with renal impairment of any etiology.

Influence of upright activity on plasma renin activity and aldosterone concentration in children

Plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were measured in 156 healthy infants and children under basal conditions of normal diet and recumbency. PRA and PAC were also evaluated during and after stimulation of the renin-angiotension-aldosterone system by postural change. Basal values of PRA significantly declined with increasing age. Postural change by standing up resulted in an increase of PRA and PAC in all age groups. The increment of PRA but not of PAC was greater in older than in younger children. Neither the basal nor the stimulated levels of PRA and PAC were influenced by sex, body weight, body surface area, serum sodium, serum potassium, creatinine, and 24-h urine secretion of sodium and potassium. Both PRA and PAC returned to the basal levels within 60 min after resuming recumbent posture.

Use of calcium excretion values to distinguish two forms of primary renal tubular hypokalemic alkalosis: Bartter and Gitelman syndromes

Clinical or biochemical findings were reevaluated in 34 pediatric patients with primary renal tubular hypokalemic metabolic alkalosis. The patients were subdivided into two groups. Bartter syndrome (primary renal tubular hypokalemic metabolic alkalosis with normocalciuria or hypercalciuria) was diagnosed in 18 patients with molar urinary calcium/creatinine ratios greater than 0.20, and Gitelman syndrome (primary renal tubular hypokalemic metabolic alkalosis with magnesium deficiency and hypocalciuria) was diagnosed in 16 patients with molar urinary calcium/creatinine ratios less than or equal to 0.20 and plasma magnesium levels less than 0.75 mmol/L. Some clinically important differences between the groups were observed. Patients with Bartter syndrome were often born after pregnancies complicated by polyhydramnios (8/18) or premature delivery (7/18) and had short stature (11/18) or polyuria, polydipsia, and a tendency to dehydration (16/18) during infancy (12/18) or before school age (18/18). Patients with Gitelman syndrome had tetanic episodes (12/16) or short stature (3/16) at school age (14/16). We conclude that the Bartter and Gitelman syndromes represent two distinct variants of primary renal tubular hypokalemic metabolic alkalosis and are easily distinguished on the basis of urinary calcium levels.

Urinary excretion of prostaglandins during infancy and childhood: influence of age, sodium restriction and posture

The influences of age, sodium restriction and posture on 24-hour urinary excretion of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF 2 alpha), 6-keto-prostaglandin F1 alpha (6-keto-PGF 1 alpha) and thromboxane B2 (TXB2) were investigated in 111 healthy children and youngsters in the age between 1 day and 16 years. A considerable degree of variation was found in normal 24-hour urinary prostaglandin excretion in all age groups. There was no significant effect of age on the urinary excretion of prostaglandins when data were corrected for body surface area. In addition, sodium restriction and posture had no influence on the excretion of PGE2, PGF 2 alpha, 6-keto-PGF 1 alpha and TXB2. Our results indicate that in the first days of life the kidney already has the capacity to synthesize prostaglandins in amounts comparable to older children.

The syndrome of hypertension and hyperkalaemia with normal glomerular function (Gordon's syndrome). A pathophysiological study

A 14-year-old boy with the syndrome of hypertension and hyperkalaemia with normal glomerular filtration rate (Gordon's syndrome) is described. The patient's clinical symptoms consisted of periodic paralysis, slight metabolic acidosis of the proximal type and hypercalciuria. Prostaglandin excretion was normal. Infusion of atrial natriuretic peptide had no effect on electrolyte excretion or glomerular function although a normal increase in cyclic guanosine monophosphate was demonstrated in plasma and urine. This lack of sensitivity to atrial natriuretic peptide offers a new pathophysiological concept in this syndrome. Treatment with hydrochlorothiazide was successful in this case.

Saliva aldosterone concentration in healthy infants

Aldosterone and glucocorticoid (cortisol + cortisone) concentrations were measured in 106 saliva samples from healthy infants. Most aldosterone values fell within the adult range (0-0.15 nmol/l (0-5.4 micrograms/100 ml)), but 10 were greater than 0.2 nmol/l (7.2 micrograms/100 ml). Aldosterone concentration was not related to sex, ethnic origin, time of collection, distress, or cortisol concentration but decreased with age.

Hyperkalemic distal renal tubular acidosis in salt-losing congenital adrenal hyperplasia

Functional indices of distal urinary acidification were assessed in two male infants, aged 1 and 3 months, with salt-losing congenital adrenal hyperplasia. In both cases the diagnosis was sustained by the presence of elevated plasma levels of 17-hydroxyprogesterone, hyponatremia, hyperkalemia, metabolic acidosis and increased plasma renin activity. Both patients were unable to lower urinary pH below 5.9 either during acute ammonium chloride-induced acidosis or after i.v. administration of furosemide. One patient also failed to decrease urine pH below 5.5 and to increase urinary potassium excretion during sodium sulfate infusion. Oral sodium bicarbonate loading was given to both patients but failed to induce a significant increase in the urine minus blood PCO2 gradient. This gradient remained low also after neutral phosphate administration. Repeated studies after acute administration of fludrocortisone in one case or after prolonged administration of hydrocortisone in the other resulted in complete normalization of all functional studies. We conclude that salt-losing congenital adrenal hyperplasia can lead to hyperkalemic distal renal tubular acidosis in early infancy. The defective renal secretion of hydrogen ion and potassium is probably related to the abolishment of the negative potential difference in the cortical collecting tubule induced by the impaired reabsorption of sodium.

Levels of renin, angiotensin I and II, angiotensin-converting enzyme and aldosterone in infancy and childhood

Basal plasma renin activity (PRA), angiotensin I and II (AI, AII), angiotensin-converting enzyme (ACE) activity and plasma aldosterone (PA) and sodium and potassium concentration were simultaneously measured in 55 healthy recumbent children aged between 1 week and 13 years. A significant (P less than 0.001) age-related decrease for PRA (r = -0.73), AI (r = -0.72), AII (r = -0.51) and PA (r = -0.71) was observed but not for ACE (r = 0.26, P = 0.06). After correction for age the correlation between PRA or PA and AI or AII was still significant (P less than 0.005). The strong correlation between AI and AII in the group as a whole (r = 0.82, P less than 0.001) and also in separate age groups, and an AI to AII ratio which was not different between the various age groups suggest that ACE activity in this age range is not rate-limiting for AII generation.