PTH is produced in the parathyroid gland, while calcitriol is made in the kidney.

甲状旁腺产甲状旁腺激，肾脏产骨三醇。

The amount of calcium and circulation is mainly regulated by two hormones parathyroid hormone(PTH) and calcitriol.

钙含量和循环主要受甲状旁腺激（PTH）和骨三醇两种激调节。

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D被运送至肾脏，在1-α-羟酶的作用下被转为1，25-二羟D，即骨三醇，它是D的活性形式。

At the same time, it stimulates production of calcitriol which promotes absorption of calcium in the small intestine, while also increases reabsorption in the kidney.

同时，它刺激骨三醇产，促进小肠对钙的吸收，同时也增加肾脏重吸收。

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；以及用于合成骨三醇，也称为1，25-二羟基胆钙固醇，又叫活性D。