%0 Journal Article
%T Saline suppression testing-induced hypocalcemia and implications for clinical interpretations.
%A Parksook WW
%A Brown JM
%A Milks J
%A Tsai LC
%A Chan J
%A Moore A
%A Niebuhr Y
%A Honzel B
%A Newman AJ
%A Vaidya A
%J Eur J Endocrinol
%V 191
%N 2
%D 2024 Aug 5
%M 39073780
%F 6.558
%R 10.1093/ejendo/lvae099
%X <B>BACKGROUND: </B>Extracellular calcium critically regulates physiologic aldosterone production. Moreover, abnormal calcium flux and signaling are involved in the pathogenesis of the majority of primary aldosteronism cases.<BR><B>METHODS: </B>We investigated the influence of the saline suppression test (SST) on calcium homeostasis in prospectively recruited participants (n = 86).<BR><B>RESULTS: </B>During SST, 100% of participants had decreases in serum calcium, with 48% developing frank hypocalcemia. Serum calcium declined from 2.30 ± 0.08 mmol/L to 2.13 ± 0.08 mmol/L (P < .001) with parallel increases in parathyroid hormone from 6.06 ± 2.39 pmol/L to 8.13 ± 2.42 pmol/L (P < .001). In contrast, serum potassium and bicarbonate did not change, whereas eGFR increased and serum glucose decreased (P < .001). Lower body surface area (translating to greater effective circulating volume expansion during SST) was associated with greater reductions in (β = .33, P = .001), and absolutely lower, serum calcium levels (β = .25, P = .001). When evaluating clinically-relevant diagnostic thresholds, participants with post-SST aldosterone levels <138 pmol/L had lower post-SST calcium and 25-hydroxyvitamin D levels (P < .05), and higher post-SST parathyroid hormone levels (P < .05) compared with those with post-SST aldosterone levels >277 pmol/L.<BR><B>CONCLUSIONS: </B>SST uniformly decreases serum calcium, which is likely to be due to the combination of variable dilution, increased renal clearance, and vitamin D status. These acute reductions in bioavailable calcium are associated with lower post-SST aldosterone. Given the critical role of extracellular calcium in regulating aldosterone production, these findings warrant renewed inquiry into the validity of SST interpretations for excluding primary aldosteronism.