Primary aldosteronism and oral contraception (OC) can both cause hypertension in young women. However, the effect of OC on the screening test for primary aldosteronism, the aldosterone to renin ratio (ARR), is not clear and has not been studied in a large cohort.
To understand how OC affects the ARR, we analysed data from the female offspring (Gen2) of women enrolled in the Raine Study, a population-based birth cohort, who had blood pressure (BP) measurements, stored blood samples for aldosterone and renin measurements, and information about OC use at age 17y and/or age 27y.
The current analyses included 484 female participants at 17y (333 OC non-users and 151 OC users) and 486 at 27y (251 OC non-users and 235 OC users). Serum aldosterone concentration was significantly higher in OC users than non-users at 17y (median 486 pmol/L vs 347 pmol/L, p<0.001). Renin concentration was significantly lower in OC-users at both 17y (13.4 mU/L vs 20.6 mU/L) and 27y (9.2 mU/L vs 11.8 mU/L), hence the ARR was significantly higher in OC-users compared to non-users at both 17y (31.5 vs 18.3) and 27y (27.3 vs 21.1). The proportion of participants with ARR > 70 pmol/mU (current threshold for PA detection) was significantly higher in OC-users at both 17y (12.6% vs 2.1%) and 27y (6.4% vs 0.4%), however, they had comparable BP to those with ARR < 70 pmol/mU. OC use at any age abolished the relationship between ARR at 17y and BP at 27y that was previously described in non-OC users1.
Overall, our data suggest that OC use can cause a false positive ARR which may lead to unnecessary investigations for primary aldosteronism. Hence, alternative contraception should be considered in women being evaluated for primary aldosteronism, especially if the initial ARR is abnormal.