Calcitriol increases renal tubular reabsorption of calcium which reduces the loss of calcium in the urine.

骨化三醇可以增加肾钙的重吸收，减少尿钙。

25-hydroxy-vitamin D then travels to the kidneys, where the enzyme 1-alpha-hydroxylase converts it to 1,25 hydroxy-vitamin D, or calcitriol, which is the active form of vitamin D.

之后25-羟维生素D被运送至肾脏，在1-α-羟化的作用下被转化为1,25-二羟维生素D，即骨化三醇，它是维生素D的活性。

The parathyroid hormone gets the bones to release calcium, and gets the kidneys to reabsorb more calcium so it's not lost in the urine as well as synthesize calcitriol also known as 1,25-dihydroxycholecalciferol also known as active vitamin D.

甲状旁腺激素作用于骨骼使其释放钙离子，也作用于肾脏而增加钙的重吸收，这样钙就不会随尿液排出；以及用于合成骨化三醇，也称为1,25-二羟基胆钙化固醇，又叫活性维生素D。