A 30 year old woman presented at 15 weeks gestation with resistant hypertension (that had been diagnosed prior to pregnancy) and hypokalaemia (2.8 mmol/l). Subsequent tests, whilst on Nifedipine, showed a markedly raised aldosterone/renin ratio of 267 (n<25) [Aldosterone 720 ng/L;Renin 3 mu/L] (Aldosterone reference range: Supine:20190 ng/L, Ambulant 30340 ng/L; Renin reference range: Supine 230 mu/L, Ambulant 340 mu/L).
Radiological investigation revealed a small 1 cm diameter adenoma in her left adrenal gland. A provisional diagnosis of Conns syndrome was considered with a view to second trimester adrenal surgery. However, she developed fulminant pre-eclampsia necessitating emergency caesarian section delivery at 25 weeks.
Post partum, her hypertension initially controlled on spironolactone resolved and she was able to stop this agent. Her potassium level also normalised without needing supplementation. 24 hour urine samples sent during her postnatal period showed a normal aldosterone/renin ratio of 12.2 ng/mu. [Aldosterone 122 ng/L;Renin 10 mu/l]. Postural studies undertaken after 5 hours of ambulation showed a ratio of 1.7 ng/mu and the renin levels went up appropriately on standing. Moreover, her urine 18 hydroxy cortisol was normal at 372 nmol/24 hours (n=40550). Further imaging did not show any change in size of the left adrenal adenoma. She has been advised to seek pre-pregnancy counseling in the future.
Primary hyperaldosteronism is rare but a recognised cause of hypertension in pregnancy. Literature review shows a number of cases, most of who needed surgical intervention postpartum to resolve hypertension. However, in a significant number of cases, laparoscopic intervention was advocated in the second trimester for an uncomplicated pregnancy and delivery. We present a case of pregnancy induced hyperaldosteronism who was spared second trimester surgery due to the development of pre-eclampsia and who appears to have a co-existent non-functioning adrenal adenoma. Our case highlights the need to exercise caution in the interpretation of aldosterone-renin measurements in pregnancy.