Serum phosphate and sympathetic tone in mild essential hypertension

Forty-year old, normocalcaemic men with mild essential hypertension (n = 35) had decreased serum phosphate (p less than 0.001) concomitant with elevated plasma adrenaline (p less than 0.03) and heart rate (p less than 0.001). All had unchanged serum immunoreactive parathyroid hormone concentrations compared to age-matched normotensive control men (n = 44). Serum phosphate levels correlated negatively with plasma adrenaline (p less than 0.05), plasma noradrenaline (p less than 0.05), mean blood pressure (p less than 0.001) and heart rate (p less than 0.05). Serum phosphate was significantly lowered by infusion of small amounts of adrenaline at all four infusion rates in a hypertensive group (n = 12) while a similar effect was obtained only at the two highest infusion rates in a normotensive group (n = 10). No change in serum calcium was observed in either group. Thus, hypophosphataemia appears to be inversely related to sympathetic tone in essential hypertension.