disturbed calcium metabolism may play an important role in the patho - physiology of essential hypertension . ionized calcium ( ca ) acts as an intracellular second messenger in excitation - contraction coupling in vascular smooth muscle ( vsm ) cells . the free intracellular calcium concentration determines the tension in vsm cells , thereby contributing to peripheral vascular resistance ( pvr ) . zidek et al . also found an increased intracellular calcium activity in normotensive subjects with a familial hypertensive disposition in comparison with normotensives without family history of htn . three extracellular calcium fractions : ionized , protein - bound , and complexed calcium are in equilibrium with one another in the serum . ionized calcium ( ca ) is the physiologically active form whereas protein - bound calcium is apparently inactive . the function of complexed calcium , which is bound to small anions such as bicarbonate , citrate , phosphate , and lactate , is uncertain . treatment of htn is multi - dimensional comprising of dietary modification , weight reduction , regular exercise , and medication . the calcium channel blockers ( ccbs ) namely nifedipine , amlodipine , diltiazem , verapamil , etc . , form one of the mainstay treatments in htn because they considerably reduce the morbidity and mortality in htn and coronary artery disease . ccbs block the voltage - gated calcium channels in vsm cells resulting in vasodilatation and decrease in peripheral resistance . since ccbs act on sarcolemma and reduce the entry of ca from extracellular fluid ( ecf ) to intracellular fluid ( icf ) , it is assumed that the serum ( extracellular ) calcium levels may be altered in hypertensive individuals who are on ccbs . this study may give an insight into the role of deranged calcium homeostasis in htn . a total of 31 individuals including 19 hypertensive patients and 12 normotensive subjects in the age group of 3570 years and belonging to both genders attending the out - patient department of general medicine were enrolled into the study after taking written informed consent and approval from institutional ethics committee . hypertensive patients were grouped into two : those who were on ccbs ( n = 9 ) and those who were on antihypertensive medication other than ccbs ( n = 10 ) . systolic blood pressure ( sbp ) more than 140 mmhg and/or diastolic blood pressure ( dbp ) more than 90 mmhg with or without previous diagnosis of hypertension were included in hypertensive group . subjects with sbp less than 140 mmhg , dbp less than 90 mmhg , and without previous diagnosis of hypertension were considered normotensive . individuals on supplementation with calcium and vitamins including vitamin d were excluded from the study . subjects with history of diabetes mellitus , ischemic heart disease , retinopathy , neuropathy , and nephropathy were also excluded . the blood pressure ( bp ) was measured in the right arm of the subject in sitting position using sphygmomanometer ( diamond company , pune , india ) after adequate relaxation . sbp and dbp were recorded , pulse pressure ( pp ) and mean arterial blood pressure ( mabp ) calculated . ionized calcium ( ca ) was measured by accucare calcium arsenazo iii kit ( lab - care diagnostics pvt . ltd . at a neutral ph , ca forms a complex with arsenazo iii , the color intensity of which is directly proportional to the concentration of calcium in the sample . statistical analysis was performed using spss version 13.0 ( spss inc . , il , usa ) and origin pro version 8.0 ( origin lab , ma , usa ) . differences between the groups were analyzed using analysis of variance ( anova ) followed by tukey honest significant difference ( hsd ) post hoc test . the blood pressure ( bp ) was measured in the right arm of the subject in sitting position using sphygmomanometer ( diamond company , pune , india ) after adequate relaxation . sbp and dbp were recorded , pulse pressure ( pp ) and mean arterial blood pressure ( mabp ) calculated . ionized calcium ( ca ) was measured by accucare calcium arsenazo iii kit ( lab - care diagnostics pvt . ltd . , sarigam , india ) according to manufacturer 's instructions . at a neutral ph , ca forms a complex with arsenazo iii , the color intensity of which is directly proportional to the concentration of calcium in the sample . , il , usa ) and origin pro version 8.0 ( origin lab , ma , usa ) . levene statistic was performed to test the homogeneity of variances . differences between the groups were analyzed using analysis of variance ( anova ) followed by tukey honest significant difference ( hsd ) post hoc test . nevertheless , in patients on ccb treatment , serum ca is more compared with patients on antihypertensive medication other than ccb but these differences are statistically not significant [ figure 1 ] . spearman 's correlation between htn and serum calcium levels is not significant ( p = 0.18 ) . demographic and test parameters of the participants differences in serum calcium levels between normotensives and hypertensives serum ca levels in different groups htn is a multi - factorial disorder in which various physiological mechanisms participate to elevate bp . many hypotheses were proposed about the possible mechanisms underlying essential htn including derangements in serum electrolytes and water balance . the present study shows no significant difference in serum calcium in hypertensive group compared with normotensive group which is consistent with the findings of kosch et al . however the results are contradictory with that of others who reported a significant decrease in serum calcium in patients with essential htn compared with normotensive subjects . serum calcium levels were significantly decreased in both males and females with essential htn and their first - degree relatives when compared with the normotensive controls . also reported reduced calcium in males with elevated dbp . in the present study the serum calcium levels did not correlate with the levels of bp . serum calcium was found to be significantly correlated with sbp only among those under the age of 40 years . abnormal cellular ion transport resulting in altered membrane control over intracellular calcium may be related to essential htn . changes in magnesium levels may contribute to altered cell membrane calcium binding in essential htn . the free intracellular calcium concentration determines the tension in vsm cells , and thus peripheral vascular resistance . increased serum calcium is observed in hyperparathyroidism , vitamin d intoxication , multiple myeloma and some neoplastic diseases of bone . decreased serum calcium is observed in hypoparathyroidism , vitamin d deficiency , steatorrhea , nephrosis , and nephritis . alternations in intracellular calcium are thought to be involved in the common pathway mediating the secretion and action of many hormones , including the pressor action of catecholamines and angiotensin ii . 25 dihydroxy vitamin d , levels of plasma renin activity , circulating ionized calcium contribute to the pathophysiology of essential htn . the effects of abnormal calcium and calcium regulating hormone levels may extend to the bp control centers of the central nervous system ( cns ) , particularly the nucleus tractus solitarius . hypertensive patients on ccb have serum calcium levels more than those on antihypertensive medications other than ccb , although the difference is statistically not significant .