Abstract
Objective Diagnosis of primary hyperaldosteronism in pregnancy is
complicated due to lack of reference ranges for aldosterone, renin and
aldosterone-to-renin ratio. We have endeavoured to establish third-trimester
reference ranges for the above-mentioned parameters.
Design & Patients We performed postural tests for aldosterone and
renin (chemiluminescence immunoassay Liason® DiaSorin Inc., Italy) in 70
healthy pregnant women (age 30.53±4.51 years), at 32.38±4.25
weeks of gestation and in 22 non-pregnant healthy women (age 33.08±8.72
years).
Results Aldosterone reference ranges were
6.51–73.97 ng/dl and
12.33–86.38 ng/dl, for supine and upright positions,
respectively and that for renin were 6.25–59.36 µIU/ml
and 11.12–82.55 µIU/ml, respectively. Aldosterone and
renin concentrations were higher in an upright position (p=0.000459 and
p=0.00011, respectively). In contrast, aldosterone-to-renin ratio was
not affected by posture (i. e.
0.497–3.084 ng/dl/µIU/ml versus
0.457–3.06 ng/dl/µIU/ml,
p=0.12), but was higher (p=0.00081) than in non-pregnant
controls. In comparison to manufacturer-provided non-pregnant reference range,
supine aldosterone concentrations increased by 556% (lower cut-off) and
313% (upper cut-off), while upright aldosterone concentrations increased
by 558% (lower cut-off) and 244% (upper cut-off). The reference
range for supine renin concentrations increased by 223% (lower cut-off)
and 48.7% (upper cut-off), while upright renin concentrations increased
by 253% (lower cut-off) and 79% (upper cut-off).
Conclusions There is an upward shift in aldosterone and renin reference
ranges in the third-trimester of pregnancy accompanied by an increase in an
aldosterone-to-renin ratio, that is not influenced by posture. It remains to be
established whether the aldosterone-to-renin ratio may be used as a screening
tool for primary hyperaldosteronism in pregnancy.
Key words
aldosterone - renin - primary aldosteronism - pregnancy - hypertension - reference range
