British Journal of Obstetrics and Gynaecology March 1977. Vol84. pp 191-196

PLASMA RENIN AND ALDOSTERONE IN PREGNANCY COMPLICATED BY ADRENAL INSUFFICIENCY BY

E. M.

SYMONDS, Professor AND

D. J. CRAVEN, Head Technician The Univtwity of Nottingham, Department of Obstetrics and Gynaecology City Hospital, Hucknall Road, Nottingham

Summary Serial measurements of plasma renin and plasma aldosterone were made throughout pregnancy in two women with adrenal insufficiency. The values were compared with levels obtained in eight normal primigravidae. Aldosterone levels were low or undetectable in adrenal insufficiency and plasma renin levels were grossly elevated in one patient with adrenal insufficiency but within the normal range in the other.

PATIENTS AND METHODS Eight primigravidae with normal, uncomplicated pregnancies were included in this study as a control group. Plasma samples were obtained at approximately monthly intervals from all patients and samples were collected between 1400 and 1500 hours with patients seated. None of these women had salt restriction or diuretics at any time during pregnancy. The two women with adrenal insufficiency were studied serially and blood samples were collected under the same conditions as the control group. One patient (Mrs K) had bilateral adrenalectomy for Cushing’s syndrome associated with an adrenal adenoma. She presented witha history of secondary amenorrhoea and subfertility and conception occurred during investigation of her subfertility. Serial blood samples were obtained at intervals of not more than one month throughout pregnancy. The first pregnancy was complicated by hypertension and proteinuria and the patient was delivered vaginally, at 36 weeks gestation, of a healthy male infant weighing 2.65 kg. Six months later the patient

NORMAL pregnancy is associated with a marked increase in the activity of the renin-angiotensin system (Helmer and Judson 1967; Skinner et al, 1972) and with an increase in the plasma levels of aldosterone (Weir el al, 1970; Bayard et al, 1970). In the non-pregnant state in Addison’s disease the plasma levels of aldosterone are low or undetectable. Renin concentration is high in untreated adrenal insufficiency (Brown et al, 1964a) but returns to the normal range when adequate replacement therapy has been instituted. In pregnancy complicated by adrenal insufficiency, urinary levels of aldosterone are low or undetectable (Gordon et al, 1954; Christy and Jailer, 1959) but plasma levels of both aldosterone and renin have not been measured simultaneously in the same patients. We now report a longitudinal study during pregnancy of plasma renin and aldosterone in two women with known adrenal insufficiency. Results have been compared with values obtained from eight primigraviclae from whom blood samples were collected under similar conditions throughout pregnancy. 191

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became pregnant again and serial blood samples were again obtained. On this occasion, the pregnancy was uncomplicated and resulted in the vaginal delivery at full term of a healthy male infant weighing 3 -38 kg. Maintenance therapy of fludrocortisone (0.1 mg daily) and cortisone acetate (25 mg twice daily) was maintained throughout both pregnancies. The second patient (Mrs P) attended the antenatal clinic when she was eight weeks pregnant. A diagnosis of Addison's disease of unknown aetiology had been made some years previously and the patient was treated with fludrocortisone (0.1 mg daily) and cortisone acetate (12.5 mg three times daily). The pregnancy was uncomplicated and serial blood samples were collected. All blood samples were collected into EDTA, centrifuged immediately at 4 "C and the plasma was separated and stored at -18 "C. All samples were assayed for plasma renin activity (PRA), plasma renin concentration (PRC), total renin concentration (TRC) and plasma aldosterone (PA) except during the first pregnancy of Mrs K when aldosterone alone was assayed. PRA and PRC were measured by radioimmunoassay of angiotensin I using a modification of Haber's method (Haber et al, 1969). The renin substrate employed in the measurement of PRC was obtained from sheep six days after nephrectomy according to the method of Skinner (1967). Renin concentration measured at physiological pH was regarded as 'active renin' whilst 'total renin' was the renin concentration measured following dialysis of the plasma to pH 3 . 3 and back to pH 7.5. Low pH treatment used initially in the method of Brown et a1 (1964b) to denature endogenous substrate and angiotensinases has been found to greatly increase PRC in pregnancy (Skinner et al, 1975). All measurements were standardized against MRC renin. PRA was expressed in ng/ml/hour whilst PRC and TRC were in units/ml (one unit being equivalent to Goldblatt units). The coefficient of variation for PRC on pooled plasma was 4.5 per cent within assays (n = 10) and 8.1 per cent between assays (n = 10). PA levels were measured by radioimmunoassay using antiserum 088 donated by the

National Institutes of Health (Bethesda). Plasma extracts were purified by paper chromatography in the system hexane : toluene : methanol : water 1 : 9 : 5 : 2 - 5 v/v. The limit of detection of aldosterone was 5 pg from the curve. Replicate assays on pooled pregnancy plasma gave 7 1 . l k 4 . 0 ng/100 ml (meanfSE) with a coefficient of variation of 14-8 per cent between assays and 9 . 9 per cent within assays. Serum sodium, potassium and chloride were measured at 10 weeks and 31 weeks gestation in Mrs P, at 20,34 and 35 weeks in the first pregnancy of Mrs K and at term in her second pregnancy. All values were within the normal range. All normal non-pregnant values were derived from 10 normal volunteers. RESULTS The mean values of PA in pregnancy are shown in Figure 1. The normal non-pregnant range is also shown on the diagram. The values in normal pregnancy were markedly elevated by 10 weeks gestation and remained high throughout pregnancy. A significant trend was established in relation to gestational age. In one patient (Mrs K), no aldosterone could be detected in the plasma during her two pregnancies, and the values do not therefore appear on the diagram. In the second patient (Mrs P), aldosterone was present in measurable quantities but concentrations were considerably lower than the normal range of values for pregnant women and fell within the normal non-pregnant range. Values for PRA are shown in Figure 2 and TRC and PRC in Figures 3 and 4, respectively. As shown in previous studies PRA, PRC and TRC in normal pregnancy were all above the normal non-pregnant range. In the adrenalectomized patient (Mrs K), all values were close to normal. The second patient (Mrs P) showed grossly elevated levels of PRA, TRC and PRC. The peak value recorded for total renin (2750 units/ml) was the highest we have recorded in pregnancy. A blood sample was collected five days post partum and although all renin values had fallen, the levels were still higher than the normal non-pregnant range.

DISCUSSION Increased levels of PRA in pregnancy, have

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been found by several investigators (Helmer and Judson, 1967; Skinner et al, 1972; Gordon et al, 1973). This increase in activity is associated with increases in both renin concentration and renin substrate. The measurement of renin concentration using procedures involving acid denaturation of endogenous substrate and the addition of known concentrations of sheep substrate has shown that renin concentration is elevated above non-pregnant levels throughout pregnancy with the highest concentrations occurring in the first 16 weeks (Brown et al, 1963; Weir et al, 1971; Skinner et al, 1972). The realization that low pH treatment of plasma increases apparent renin concentration in pregnancy has raised the possibility that renin may occur in a biologically inactive form and the measurement of PRC without using acid denaturation has led to the measurement of ‘active renin’ as well as ‘total renin’ concentration (Skinner el a/, 1975; Symonds, 1976). Our study of normal subjects has confirmed previous observations and, in particular, has shown that the levels of ‘active’ renin follow a similar pattern to those of PRA.

Measurements of aldosterone, either in urine or plasma, have previously shown markedly increased levels in pregnancy (Watanabe el al, 1963; Weir et al, 1971). Our values are similar to those of Weir et a1 (1971). However, the greatest increase in our series appeared to occur between 29 to 32 weeks. Adrenal insufficiency in the non-pregnant state is associated with low or undetectable levels of aldosterone or its metabolites in urine and plasma. In the uncontrolled state, very high levels of plasma renin may occur (Brown et al, 19643) and tend to fall with adequate replacement therapy. Brown et a1 (1968) described two cases of untreated Addison’s disease associated with abnormally low plasma sodium levels where PRC was high. Steroid replacement therapy was acdompanied by correction of plasma electrolytes and a fall in PRC. Hypoaldosteronism may also occur associated with low plasma renin levels where the primary defect appears to be in renin secretion (Schambelan et al, 1972). Several reports have shown that negligible amounts of aldosterone appear in the urine of women with Addison’s disease during pregnancy (Gordon et al, 1954; Christy and Jailer, 1959). Our observations on PA levels in the woman with a bilateral adrenalectomy showed that no aldosterone was detectable within the sensitivity of the assay throughout the two pregnancies. In the second patient with partial adrenal function, PA levels were below two standard errors of the mean of normal pregnancy. Although an increase was noted at 34 weeks gestation in a pattern similar to normal pregnancy, the levels fell within the normal non-pregnant range. These findings suggest that there is little or no fetal or placental contribution to maternal aldosterone levels. Gordon et a1 (1954) have previously described pre-eclampsia in a woman with adrenal insufficiency. One of our patients (Mrs K) developed hypertension, proteinuria and gross generalized oedema during her first pregnancy and no aldosterone was detected in her plasma at any time. These findings suggest that aldosterone is unlikely to be the steroid involved in the formation of oedema in pre-eclampsia. Recent studies on pregnancy hypertension and PA levels (Weir et al, 1973) have shown

PLASMA RENIN AND ALDOSTERONE IN PREGNANCIES WITH ADRENAL INSUFFICIENCY

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that levels appear to be suppressed in pregnancy hypertension. In the patient with partial adrenal insufficiency, grossly elevated levels of PRA, TRC and PRC were found throughout pregnancy suggesting an altered sodium and water balance. An increase in sodium loss would lead to raised levels of plasma renin particularly in adrenal insufficiency when increased renin-angiotensin system activity tends to compensate for low aldosterone values. Our patient with partial adrenal insufficiency had a normal pregnancy with blood pressure and serum electrolyte values within normal limits. Plasma samples obtained from one subject (Mrs P) at five days arid 8 months post partum showed elevated PRA, PRC and TRC levels. Thus, abnormally high levels of renin may occur in adrenal insufficiency in pregnancy

0 ) .Means

and may provide an indication for the need to adjust replacement therapy. ACKNOWLEDGEMENTS We gratefully acknowledge the assistance of Dr M. Anstey and Mrs J. Adcock with the aldosterone assay and Miss A. Tansley with the renin assays. REFERENCES Bayard, F., Arces, I. G., Tapper, A. J., Weldon, V. V., Kowarski, A., and Migeon, C . J. (1970): Journal of Clinical Investigation, 49, 1389. Brown, J. J., Davies, D. L., Doak, P. B., Lever, A. F., and Robertson, J. I. S . (1963):Lancet, 2 , 900. Brown, J. J., Davies, D. L., Lever, A. F., and Robertson, J. I. S. ( 1 9 6 4 ~ ) :Canadian Medical Association Journal, 90, 201. Brown, J. J., Davies, D. L., Lever, A. F., Robertson, J. I. S., and Tree, M. (19646): Biochemical Journal, 93, 594.

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Brown, J. J., Fraser, R., Lever, A. F., Robertson, J. I. S., and James, V. H. T. (1968): Quarterly Journal of Medicine, 145, 97. Christy, N. P., and Jailer, J. W. (1959): Journal of Clinical Endocrinology and Metabolism, 19, 263. Gordon, E. S., Chart, J. J., Hagedorn, D., and Shipley, E. G. (1954): Obstetrics and Gynecology, 4, 39. Gordon, R. D., Symonds, E. M., Wilmshurst, E. G., and Pawsey, C. G. K . (1973): Clinical Science and Molecular Medicine, 45, 115. Haber, E., Koerner, T., Page, L. B., Klinman, B., and Durrode, A. (1969): Journal of Endocrinology, 29, 1349. Helmer, 0. M., and Judson, W. E. (1967): American Journal of’Obstetrics and Gynecology, 99, 9. Schambelan, M., Stockigt, J. R., and Begteri, E. G. (1972): New England Journal of Medicine, 287, 573. Skinner, S. L. (1967): Circulation Research, 22, 391. Skinner, S. L., Cran, E. J., Gibson, R., Taylor, R., Walters, W. A. W., and Colt, K. J. (1975): American Journal of Obstetrics and Gynecology, 121, 626.

Skinner, S. L., Lumbers, E. R., and Symonds, E. M. (1972): Clinical Science, 42, 479. Symonds, E. M. (1976): Pregnancy in Hypertension. Edited by M. Lindheimer. J. Wiley and Sons, Chichester, p 271. Watanabe, M., Meeker, M. I., Gray, M. J., Sims, E. A. H., and Solomon, S. (1963): Journal of Clinical Investigation, 42, 1619. Weir, R. J., Fraser, R., Lever, A. F., Martin, J. J., Brown, J. J., Kraszenski, A., Mcilwaine, G. M., Robertson, J. I. S., and Tree, M. (1973): Lancet, 1, 291. Weir, R. J., Paintin, D. B., Brown, J. J., Lever, A. F., Robertson, J. I. S., and Young, J. (1971): Journal of Obstetrics and Gynaecology of’the British Commonwealth, 78, 590. Weir, R. J., Paintin, D. B., Fraser, R., Robertson, J, I. S., Tree, M., and Young, J. (1970): Proceedings of the Royal Society of Medicine, 63, 101.