0021-972x/92/7503-0895$03.00/0 Journal of Clinical Endocrinology and Metabolism Copyright 0 1992 by The Endocrine Society

Vol. 75, No. 3 Printed in U.S.A.

Timing and Magnitude of Response of Plasma Aldosterone Concentration to Bolus Adrenocorticotropin: Importance of Sodium Balance in Outpatient Testing* CHRISTOPHER M. CORSI, JOSEPH M. HUGHES From the Department of Internal Cooperstown, New York 13326

DAVID Medicine,

L. GALLAGHER,

PHILIP

The Mary Imogene

J. DZWONCZYK,

AND

Bassett Hospital,

ABSTRACT Plasma aldosterone concentration (PAC) response to ACTH is utilized in clinical and experimental protocols. However, PAC response to ACTH in normal subjects controlled for modifiers of PAC has not been established. Our report includes two experiments. In both, subjects were studied in the morning and were in sodium (Na’) balance prior to study on 4 g Na+ for phase I, and 2 and 8 g Na+ diets for phase II. Na+ balance was established by 24-h urinary Na+ (UNa’) in phases I and II, and also by fractional excretion of Na’ (FENa+) in phase II. After being supine for 60 min, subjects received 0.25 mg of iv bolus ACTH. PAC, plasma renin activity and plasma potassium (K+) were drawn every 30 min in phase I and every 15 min in phase II. The rise in PAC (rPAC) and correlation coefficients were calculated.

In phase I, peak PAC occurred at 30 min, 1130 + 420 pmol/L, with a rPAC of 810 + 310 pmol/L. Twenty-four hour UNa+ was 86 + 45 mmol/24 h. In phase II, time and magnitude of peak PAC and rPAC were dependent on diet. Both occurred at 30 min for 8 g Na+: peak PAC was 640 f 210 pmol/L and rPAC was 440 + 190 pmol/L; and at 60 min for 2 g Na’: peak PAC was 1040 + 320 pmol/L and rPAC was 690 & 220 pmol/L. Correlation coefficients for rPAC and 24-h UNa+ was r = -0.44, P less than 0.05 and for rPAC and FENa+ was r = -0.46, P less than 0.05. In summary, in subjects supine for 60 min prior to iv bolus ACTH, Na’ balance is the most important determinant of PAC response. Both magnitude and timing of rPAC is influenced by Na’ balance. Finally, both 24-h UNa’ and FENa’ are valid for establishing pretesting Na+ status. (J Clin Endocrinol Metab 75: 895-900, 1992)

T

(FENa+) was calculated to determine if that, too, correlates with PAC responseto ACTH.

HE RESPONSE of plasma aldosterone concentration (PAC) to ACTH can be used clinically in distinguishing primary from secondary adrenal insufficiency and in evaluating patients with suspectedisolated aldosterone deficiency (1,2). It has alsobeen used as a researchtool for investigating early adrenal dysfunction in patients with the acquired immune deficiency syndrome (3). Even though used in clinical testing, the expected PAC response to bolus iv ACTH in normal subjects controlled for known modifiers of PAC is unclear. Our study is divided in two parts and attempts to establishan outpatient protocol for measuring PAC response to ACTH. In both phases,we studied normal subjects controlled for posture, time of day, plasma potassium (K+) and total body sodium (Na*) balance, which was assessedby 24-h urinary sodium (UNa+). In phaseI, wide variability of UNa+ occurred despite subjects’reported compliance with dietary instruction in a 4-g Na+ diet. Therefore, in phase II of the study, subjects were studied while on 2 and 8 g Na+ diets in order to establish a wide range of UNa’ to correlate with PAC responseto ACTH. Furthermore, fractional excretion of sodium Received October 9, 1991. Address all correspondence and requests for reprints to: Joseph M. Hughes, M.D., The Mary Imogene Bassett Hospital, Cooperstown, New York 13326. * Support provided by Stephen C. Clark Research Fund. This information was presented, in part, at the 71st and 72nd Annual Meetings of The Endocrine Society: Seattle, Washington, 1989 and Atlanta, Georgia, 1990.

Subjects

and Methods

Both protocols were approved by the Investigational Review Board of The Marv Imoaene Bassett Hosnital. Coouerstown. NY. The two phases of the stud; were separated by approximately 1 yr. In phase I, after informed consent, six male and six female volunteers, age 26-47 yr, were studied in a 7-day, single blind, randomized protocol, Female subjects were tested irrespective of the time in their menstrual cycle. Throughout the 7 days, subjects maintained a 4-g Na+ diet, based on provided dietary literature. Twenty-four hour urine was collected for UNa+, potassium (UK+), and creatinine during day 5. On day 6, subjects came to the hospital, were weighed and became supine, and a heparin lock was placed in an antecubital vein at -180 min, 0700 h. Systolic and diastolic blood pressure, pulse rate (P), and blood for plasma renin activity (PRA) and PAC were obtained at -180, -90, -60, and -30 min. At time 0 min, subjects randomly received either 1.0 mL iv bolus injection of saline vehicle or 0.25 mg Cortrosyn (ACTH). Plasma cortisol concentration (F), I’RA, PAC, K+, blood pressure, and P were obtained at 0, 30, 60, and 90 min. A blood chemistry profile, including Na+, creatinine (Cr), and liver chemistries, was obtained at 0 min. Day 7 was identical to day 6 except that heparin locks were placed and blood sampling began at 0 min, and subjects received the opposite agent. Phase II involved six male and six female normal volunteers, age 1% 37 yr, five of whom had been studied in phase I. In this phase, subjects were studied first after 7 days of 2-g Na+ diet, and then after 7 days of 8-g Na+ diet, again based on provided dietary instruction. Based on results from phase I, the protocol was modified for phase II in the following ways: testing took place on day 7 of each diet since no vehicle was needed and, therefore, 24-h urines were collected on day 6 rather than day 5; subjects were supine for only 60 min prior to testing; blood sampling occurred at -15, 0, 15, 30, and 60 min; a spot urine was

895

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CORSI ET AL.

896

obtained when subjects became supine at -60 min for Na’, K+, and Cr; and liver chemistries were not obtained. In both phases, blood samples remained on ice until centrifugation, and plasma was frozen until analysis. PRAs were assayed in duplicate using the Gamma Coat ‘251-PRA RIA kit (Baxter Healthcare Corp., Camden, MA). Fs were assayed in duplicate using the Corti-Cote cortisol solid phase component system (Becton Dickinson Immunodiagnostics, Orangeburg, NY). PACs were assayed in duplicate using the Coat-ACount I’AC RIA kit (Diagnostic Products Corp., Los Angeles, CA). This kit involves use of an aldosterone antibody with cross-reactivities of 0.06% with 1 I-deoxycorticosterone, 0.002% with corticosterone, 0.033% with 18-OH-corticosterone, and 0.1% with 18-OH-deoxycorticosterone. Na’, K+, and Cr were analyzed by the Kodak Ektachem system.

Data analysis and formula Data is presented as mean + SD, and has been analyzed by paired t test or analysis of variance (Newman-Keuls). Correlation coefficients were calculated using Pearson’s R technique. P values less than 0.05 are considered significant. The following equations were used. In phase I: Delta

PAC

(APAC) = (PAC

at time

X after

ACTH)

- (matched

control

PAC)

In phase II: FENa+

= (spot urine (spot urine

Na+ x plasma Cr) Cr X plasma Na’)

(SAC) = (PAC

at time

X after

ACTH)

- (PAC

at time

0)

Results Phase I

PAC decreased to baseline at -120 min, 60 min after becoming supine, 320 + 190 pmol/L (11.6 + 6.8 ng/dL) (Fig. 1 and seeFig. 7). PAC was 320 + 240 (11.5 + 8.5) at 0 min and peaked 30 min after receiving ACTH, 1130 f 420 (40.6 & 15.0) compared with time matched control of 300 f 230 pmol/L (10.8 f 8.1 ng/dL) (P < 0.00001). PAC remained elevated after ACTH at 60 min, 970 & 420 (35.1 + 15.0) and 90 min, 840 + 390 pmol/L (30.4 f 14.2 ng/dL). O-O 0-O

APACs and rPACs were calculated. APAC peaked at 30 min, 830 f 310 (29.8 + 11.3), as did rPAC, 810 + 310 pmol/ L (29.2 + 11.0 ng/dL). APAC was equivalent to rPAC at 30, 60, and 90 min (Table 1). The range of maximum rPAC was 194 to 1134 pmol/L (7.0-40.9 ng/dL). The rPAC for males was 760 + 310 (27.4 f 11.2) compared with 890 f 340 pmol/L (32.1 f 12.3 ng/dL) for females, P = NS. PRA, like PAC, fell to baseline 60 min after becoming supine, at -120 min, 0.64 + 0.44 ng(L.s) (2.3 + 1.6 ng/mL/ h). At 0 min, PRA was 0.60 + 0.52 ng(L.s) (2.2 + 1.9 ng/ mL/h) and was then unchanged throughout the experimental period. Mean UNa+ was 86 ? 45 mmo1/24 h, and was 79 f 42 for malesand 95 + 49 mmo1/24 h for females,P = NS (Table 2). Mean UK+ was 65 + 24 mmo1/24 h. Plasma K+ was the sameon ACTH and control days at 0 min, 4.2 + 0.2 and 4.1 + 0.2 mmol/L (P = NS) and at time of peak PAC, 30 min, 4.1 + 0.3 and 4.0 f 0.2 mmol/L (P = NS). After ACTH, F was significantly increased at 30 min and 60 min, but peaked at 90 min, 800 f 220 (29.1 f 7.8) compared with F at 0 min, 270 + 140 nmol/L (9.7 f 4.9 ng/dL) (P < 0.00001). Mean arterial pressure (MAP) and P were unchanged throughout the study. Phase II

In both phases: Rise in PAC

JCE & M. 1992 Vol75.No3

In phase II, UNA+ was significantly lessfor 2 g, 87 & 47, than for 8 g Na+ diet, 206 + 73 mmo1/24 h (P < 0.005). The range of UNa’ was 17-173 for 2 g and 97-322 mmo1/24 h for 8 g. UNa+ on 2 g for males was 98 + 59 and 76 f 34 mmo1/24 h for females, P = NS; while for 8 g for maleswas 248 + 64 compared to 164 + 59 mmo1/24 h for females, P = NS (Table 2). Calculated FENa+ was less for 2 g, 0.3 f 0.2, than for 8 g Na+ diet, 0.6 + 0.3% (P < 0.005). The range of FENa+ was 0.01-0.6 for 2 g and 0.2-1.0% for 8 g. UK+s were equivalent for the two diets, 77 + 23 for 2 g and 77 + 32 mmo1/24 h for 8 g (P = NS). TABLE 1. Phase concentration

I. Comparison APAC (w/dL)

Time (min) 0 30 60 90

ACTH Vehicle

a PAC ’ PAC

at time at time

1.0 29.8 23.1 18.2

-180

FIG. 1. Mean -180 min and circles represent

-120

-60

-30

Time

(min)

0

From phase I, PAC after after receiving ACTH at 0 min PAC after vehicle at 0 min.

(&SD).

30

60

90

becoming supine at (open circles). Solid

+ + + +

5.8 11.3 9.0 8.9

X - matched control X - PAC at time 0.

TABLE 2. Comparison of the study Diet

of change

St%

aldosterone

rPAC* bg/dL)

P value

29.2 + 11.0 23.6 + 10.3 19.0 f 9.9

NS NS NS

PAC.

of male and female

UNa’

in plasma

(mmo1/24

subjects

h)

for both

phases

Maximum rPAC WdL)

2 gm Na+

Male Female

98 + 59 76 + 34

20.9 f 5.4” 28.8 k 8.3

4 gm Na’

Male Female

79 + 42” 95 k 49”

27.4 + 11.2” 32.1 f 12.3”

8 gm Na’

Male Female

248 + 64” 164 + 59”

12.6 2 5.4” 19.5 f 6.5”

“P=NS.

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PLASMA

ALDOSTERONE

CONCENTRATION

At 0 min PAC was greater for 2 g, 360 + 210 (12.9 + 7.5), than 8 g Na+ diet, 200 f 90 pmol/L (7.2 + 3.1 ng/dL) (P < 0.05). When compared to time 0 min, PAC by 15 min had increasedsignificantly for both 2 g, 780 + 290 pmol/L (28.1 + 10.4) (P < 0.05) and 8 g Na+ diet, 490 + 140 pmol (17.8 f 4.9 ng/dL) (P < 0.05), (Table 3). The peak response occurred at 30 min for 8 g, 640 + 210 pmol/L (23.1 + 7.6) and at 60 min for 2 g Na+ diet, 1040 + 320 pmol/L (37.6 + 11.5 ng/dL) (Fig. 2 and seeFig. 8). Calculated rPAC peaked at 30 min for 8 g and at 60 min for 2 g Na+ diet (Fig. 3). Maximum rPACs were 440 & 190 (15.9 + 6.7) for 8 g and 680 + 220 pmol/L (24.7 + 7.9 ng/dL) (P < 0.005) for 2 g. Range of maximum rPAC was 230 to 850 (8.1-30.5) for 8 g and 380-1070 pmol/L (13.7-38.4 ng/dL) for 2 g. The mean rPAC for maleson 2 g was 580 Ifr 150 (20.9 + 5.4) VS.800 f 230 pmol/L (28.8 + 8.3 ng/dL) for females P = NS; while for males on 8 g was 350 + 150 (12.6 + 5.4) compared to 540 f 180 pmol/L (19.5 + 6.5 ng/dL) for females, P = NS (Table 2). PRA at 0 min, was 0.53 f 0.36 (1.9 + 1.3) for 2 g and 0.33 f 0.33 ng(L.s) (1.2 f 1.1 ng/mL/h) for 8 g Na+ diet (P = NS). PRA did not change during the study periods. Correlation coefficients were calculated for FENa+ and 24h UNa+, r = 0.48 (P < 0.05); rPAC and 24-h UNa+, r = -0.44 (P < 0.05) (Fig. 4); and rPAC and FENa+, r = -0.46 TABLE sodium

3. Phase diets

II. Comparison

of subjects

while

Weight (kg) UK+ (mmo1/24 h) FENa+ (%) UNa’ (mmo1/24 h) Range of UNa+ (mmo1/24 PRA-0 min (ng/mL/h) PAC-0 min (ng/dL) rPAC-15 min (ng/dL) rPAC-30 min (ng/dL) rPAC-60 min (ng/dL) 60

50

h)

71.2 77 + 23 0.3 + 0.2 87 3~ 47 17-173 1.9 + 1.3 12.9 + 7.5 15.2 f 7.6 22.4 + 8.4 24.7 k 7.9

1

30 i

rPAC be/dl)

”

10 -

0L 0

(5

Time (mm) FIG.

with

3. Mean (&SD). From phase II, calculated rPAC at 15, 30,60 subjects on 2 g (open bars) and 8 g Na+ diets (solid bars).

min

60

50 I

P value 8g 72.4 77 + 0.6 f 206 + 97-322 1.2 + 7.2 + 10.6 f 15.9 + 15.7 +