Parathyroid hormone suppression by intravenous calcitriol: role of phosphate, calcium, race and diabetes.
BACKGROUND
Parathyroid hormone (PTH) suppression in patients with end-stage renal disease (ESRD) undergoing maintenance hemodialysis is achieved largely by the use of intravenous calcitriol. Aspects of the utility and efficacy of this therapy remain controversial. It is debated whether oral versus intravenous therapy is more effective. Most existing studies examine the effect of calcitriol in isolation, without adjusting for other factors that might influence PTH levels. Thus, the simultaneous role of factors such as dosing, control of serum calcium and phosphorus, and demographic variables such as age, sex, race, and duration of ESRD is not well understood.


METHODS
We examined the relationship between the administration of calcitriol and PTH suppression in a cohort of hemodialysis patients at a large urban dialysis facility over a period of 30 months. Hemodialysis patients (n = 155) who received at least 3 months of treatment in this facility were included.


RESULTS
Using a time sensitive multiple linear regression modeling technique, we found that second and subsequent PTH levels were positively correlated with black race (P < 0.0001) and serum phosphate (P < 0.03) and strongly negatively correlated with serum calcium (P< 0.0001) and diabetes (P< 0.0039). Drug dose (in micrograms per kilogram per month) was weakly negatively correlated (P < 0.04). Unlike previous studies, we adjusted for the simultaneous confounding influence of demographic and laboratory variables, as well as for drug dose normalized for body weight.


CONCLUSIONS
This analysis suggests that calcitriol therapy in hemodialysis patients is adversely affected by higher phosphate levels and needs to account for such patient characteristics as race and diabetes and such laboratory variables as calcium and phosphate control. Finally, as has been recently suggested by others, the patient's race may require us to aim for different PTH target levels with therapy.
Kant
K Shashi
KS
Department of Internal Medicine, University of Cincinnati College of Medicine, Ohio 45267-0585, USA. shashi.kant@uc.edu
Cook
E Francis
EF
Duncan
Heather
H
Freyberg
Ron
R
D000465:Algorithms; D044383:Black People; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D003920:Diabetes Mellitus / Q000378:metabolism*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D010281:Parathyroid Hormone / Q000096:biosynthesis*; D010710:Phosphates / Q000378:metabolism*; D006435:Renal Dialysis; D012737:Sex Factors; D013997:Time Factors; D044465:White People
D002120:Calcium Channel Agonists; D010281:Parathyroid Hormone; D010710:Phosphates; D002117:Calcitriol; D002118:Calcium