Abstract
<title>Abstract</title> <p>Background. Calcium and phosphorus homeostasis influences vascular tone and blood-pressure regulation, yet the integrated calcium–phosphorus (Ca/P) ratio is seldom studied in essential hypertension, and prior reports rarely exclude renal or endocrine confounders or relate minerals to formally graded severity. We evaluated serum calcium, phosphorus and the Ca/P ratio and their association with hypertension severity and electrocardiographic target-organ damage. Methods. In this cross-sectional study at a tertiary centre in Chengalpattu, 171 adults with primary hypertension—after excluding renal, endocrine, secondary-hypertensive, hepatic, pregnant and supplement-using patients—underwent measurement of total calcium (colorimetric), phosphorus, and the calculated Ca/P ratio and Ca×P product. Blood pressure was graded by the ESH 2023 guideline and target-organ damage by electrocardiography. Analyses used non-parametric tests, multi-method correlation and multivariable ordinal regression, with pre-specified robustness analyses (isometric log-ratio modelling, distance correlation, E-values, specification-curve analysis and penalised regression). Results. Mean calcium was 8.88 ± 0.69 and phosphorus 3.11 ± 0.56 mg/dL; hypocalcaemia occurred in 15.2%. From grade 1 to grade 3, phosphorus fell and the Ca/P ratio rose monotonically (Jonckheere trend p < 0.001 and p = 0.0005), while calcium showed only a borderline, non-significant decline (trend p = 0.050). The Ca/P ratio correlated positively, and phosphorus negatively, with blood pressure (|ρ| 0.20–0.28). After adjustment, each unit of Ca/P more than doubled the odds of higher grade (OR 2.50, 95% CI 1.35–4.63, p = 0.003); compositional modelling pointed to overall mineral magnitude—driven by phosphorus—rather than the calcium-to-phosphorus balance, although the two coordinates were collinear and could not be cleanly separated. The effect was significant in 88% of 32 specifications (E-value ≈ 1.7). No mineral discriminated electrocardiographic left ventricular hypertrophy (AUC 0.53–0.57). Conclusions. The Ca/P ratio rises with hypertension severity, driven by declining phosphorus rather than rising calcium; total calcium was neither depressed nor severity-related, and minerals did not predict left ventricular hypertrophy. This robust but modest association warrants confirmation using ionised calcium and echocardiography.</p>