The serum @ ( OH ) D concentration was the primary outcome , and serum calcium , parathyroid hormone ( PTH ) , @,@-dihydroxyvitamin D -LSB- @,@ ( OH ) D -RSB- , @,@-dihydroxyvitamin D -LSB- @,@ ( OH ) D -RSB- , the ratio of @,@ ( OH ) D to @ ( OH ) D , vitamin D-binding protein , and free @ ( OH ) D were exploratory outcomes .