Overview of PTH

By Donna Swartzendruber, MSN, RN, CNN

What is PTH?

PTH stands for parathyroid hormone. If you are on dialysis, you will recognize it as one of your routine blood tests. This hormone is made by your parathyroid glands. These small glands are located behind the thyroid gland in your neck. 

The key purpose of the parathyroid glands is to keep the calcium and phosphorus in the blood at a constant, normal level. If, for example, the blood calcium becomes low, the parathyroid gland will respond by secreting more PTH. This extra PTH then will pull calcium from the bones, correcting the low blood level. This give-and-take response works well until kidney failure begins to occur. 

What happens to PTH when kidneys fail?

There are several reasons why an increase in PTH is common with kidney failure. As blood phosphorus levels rise, so do PTH levels. Second, the diseased kidney cannot activate vitamin D. Without activated vitamin D, calcium cannot be absorbed from your intestines into your blood. When the blood calcium level drops, the parathyroids respond by producing more PTH. Hyperparathyroidism (an enlargement of the glands) often develops. Then, even more PTH is produced.

What are the signs and symptoms of hyperparathyroidism (enlarged, overactive parathyroids)?

  • PTH levels become high.
  • Bones weaken. This may cause bone pain and fractures.
  • Calcification of tissues and organs can occur throughout the body. The lungs, heart, blood vessels, joints and skin may be affected.

How can these problems be avoided?

  • Keeping your phosphorus below 5.5 is one key way to decrease problems. Both diet and phosphate binders can help.
  • Medications with vitamin D can be given. Zemplar®, Hectorol®, and calcitriol are medications that are often used. A medication called Sensipar® is also available. It works directly on the parathyroid to decrease PTH production. It comes as a pill and is taken at home.

Can my PTH level ever be too low?

A normal PTH level is 10-65 pg/mL. As kidney function declines, PTH level gradually increases. For a person on dialysis, if the intact PTH is less than 100 pg/ml, this is known as adynamic bone disease (or low bone turnover). Bone weakening and bone fractures are again common. Low bone turnover may happen if the parathyroid glands become overly suppressed with vitamin D medication, such as Zemplar or Hectorol.

About Donna Swartzendruber

Donna Swartzendruber, MSN, RN, CNN, is an Education Project Specialist and a member of DaVita’s Clinical Education Team.