The Effect of Thiazide Diuretics on Urinary Prostaglandin E2 Excretion and Serum Sodium in the General Population

CONTEXT: Thiazide-induced hyponatremia is one of the most common forms of hyponatremia, but its pathogenesis is incompletely understood. Recent clinical data suggest links with prostaglandin E2 (PGE2) and a single nucleotide polymorphism (SNP) in the prostaglandin transporter gene (SLCO2A1), but it is unknown if these findings also apply to the general population. OBJECTIVE: To study the associations between serum sodium, thiazide diuretics, urinary excretions of PGE2 and its metabolite (PGEM), and the rs34550074 SNP in SLCO2A1 in the general population. DESIGN: Prospective population-based cohort study (Rotterdam Study). SETTING: General population. PARTICIPANTS: 2,178 participants (65% female, age 64 ± 8 years). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Serum sodium levels. RESULTS: Higher urinary PGE2 excretion was associated with lower serum sodium: difference in serum sodium for each two-fold higher PGE2 -0.19 mmol/l (95%CI -0.31 to -0.06), PGEM -0.29 mmol/l (95%CI -0.41 to -0.17). This association was stronger in thiazide users (per two-fold higher PGE2 -0.73 vs. -0.12 mmol/l and PGEM -0.6 vs. -0.25 mmol/l, p for interaction < 0.05 for both). A propensity score matching analysis of thiazide vs. non-thiazide users yielded similar results. The SNP rs34550074 was not associated with lower serum sodium or higher urinary PGE2 or PGEM excretion in thiazide or non-thiazide users. CONCLUSIONS: Serum sodium is lower in people with higher urinary PGE2 and PGEM excretion and this association is stronger in thiazide users. This suggests that PGE2-mediated water reabsorption regulates serum sodium, which is relevant for the pathogenesis of hyponatremia in general and thiazide-induced hyponatremia in specific.