High urinary cAMP in hypertensives despite careful drug treatment--an epidemiological study from the Dalby population. The correlation between serum calcium (S-Ca), plasma parathyroid hormone (P-PTH) and hypertension was determined in a population-based, cross-sectional study of carefully treated hypertensives (n = 391; diastolic blood pressure 90.2 mmHg; 57 years) compared with normotensive controls (n = 328; diastolic blood pressure 82.1 mmHg; 57 years). Levels of urinary cyclic-adenosinemonophosphate (U-cAMP), but not of plasma cAMP (P-cAMP), were higher (P less than 0.001) in hypertensives than in controls. This was the case regardless of the type of drug treatment and the blood pressure level that was reached. U-cAMP correlated with adrenaline in multivariate analyses. S-Ca levels were higher (P less than 0.001) and S-Mg levels were lower (P less than 0.001) in hypertensives than in controls. This was not explained by thiazide treatment. Thus, despite 'adequate' blood pressure reduction, substantial differences in S-Ca, S-Mg and U-cAMP still exist between hypertensives and normotensive controls. 