R013

Primary hyperaldosteronism in pregnancy

Jarvis S, Rahman M, Steer K, Rudra T, Remedios D, Cheng F  Palazzo F and Williamson C

Abstract:

A 32 year old lady (Para 3+0) was referred to the obstetric medicine clinic at 14 weeks gestation whilst under investigation for primary hyperaldosteronism.  She presented the previous year with paraesthesia, mild hypertension and hypokalaemia. An MRI scan revealed a 16mm left adrenal adenoma and subsequent investigations suggested primary hyperaldosteronism (aldosterone to renin ratio >3050). Treatment with labetalol, nifedipine and oral potassium supplementation was initiated, but she remained hypertensive (135/95) and ophthalmoscopy demonstrated arteriovenous nipping.  Amiloride was added for  potassium-sparing. Her serum potassium was in the normal range whilst taking this treatment regimen. There was a multidisciplinary team meeting that involved endocrinologists, an endocrine surgeon and obstetric physician and the consensus was to medically manage the patient. She will have weekly measurements of serum electrolytes and blood pressure in addition to performing home blood pressure monitoring. If the hypertension or hypokalaemia becomes difficult to manage medically she may require a second trimester laparoscopic adrenalectomy with preceding adrenal vein sampling.

There are only a small number of cases of primary hyperaldosteronism in pregnancy reported in the literature.  During normal pregnancy, up-regulation of the renin-angiotensin-aldosterone system increases plasma aldosterone concentrations and renin activity, which can make accurate diagnosis difficult. Progesterone antagonizes the renal action of aldosterone and this may explain improvement of symptoms in some pregnant women. However, there are reports of worsening hypertension and hypokalaemia, necessitating close surveillance.  Medical management of this condition tends to be favored in the literature, although successful adrenalectomy has been reported. A number of antihypertensive drugs may be used safely in pregnant women, including beta-blockers, calcium antagonists and methyldopa. There are fewer data about potassium-sparing diuretics, but there is a clear rationale for the use of amiloride in our case and there are no reports of adverse fetal outcome. Spironolactone should be used with caution in pregnancy due to concerns about feminization of the male fetus (reported in rats). Fetal sexing will be performed for this case in case other antihypertensive agents fail to control the blood pressure.  Regular assessment of fetal growth will be performed as the uteroplacental blood supply will be adversely affected if the blood pressure becomes inappropriately low.

There are reports of emergency Caesarean section in the case of hyperaldosteronism where pregnant women develop refractory hypertension or fetal compromise. In addition, placental abruption was reported in 21% of medically managed cases in one series. Operative delivery will be considered should this case develop medical or obstetric complications that necessitate Caesarean section. However, this woman had three previous uncomplicated vaginal deliveries so it will be more appropriate to induce labour if she is medically stable. Maternal deterioration has been reported in the immediate post-delivery period, likely secondary to removal of high gestational levels of progesterone and therefore close surveillance is essential after delivery.