Results from KDOQI guidelines, parathyroid hormone (PTH) level within target range is 150-300pg/ml. Both lower PTH levels and higher PTH levels were associated with higher risk of all-cause mortality. However, in out of target range, it is still unknown which mortality higher. so, in this prospective, observational clinical trial study. the investigators will observe the mortality and cardiovascular incidence rate between SHPT(>800pg/ml) and low serum PTH levels(<60pg/ml). Both two groups of patients will receive a reasonable treatment according to the suggestions in K/DOQI guidelines.

It is common that the abnormalities in parathyroid hormone (PTH) levels appear in patients with moderate and advanced chronic kidney diseases (CKD). CKD-mineral and bone disorder (CKD-MBD), manifested by the serum calcium (Ca), phosphorus (P), and parathyroid hormone (PTH) levels, and other abnormalities such as vitamin D metabolism and bone turnover etc, contribute to the increased morbidity and mortality in patients on maintenance dialysis.

Results from KDOQI guidelines, indicated that an increased mortality risk was associated with high parathyroid hormone (PTH) levels, if the PTH levels >600pg/ml, it means severe secondary hyperparathyroidism, it have been shown to contribute to alterations of arterial structure and function and associated with cardiovascular (CV), calcifications, CV events, and death.

In most patients, SHPT can be successfully controlled by dialysis and supplements of calcium and vitamin D. but Results from several studies, the severe secondary hyperparathyroidism can't be control by medical treatment or hemodialysis, about 15% of patients after 10 years and 38% of patients after 20 years of dialysis need parathyroidectomy. total parathyroidectomy(tPTX) is the best Surgical approach. tPTX seems to be associated to a lower relapse rate but higher percentage of hypoparathyroidism. But it may cause the patient in low parathyroid hormone status.

It is well known that at present, a high proportion of patients receiving dialysis therapy have relatively low serum PTH levels. In parallel, the observation that CV calcifications are more prevalent in patients undergoing dialysis who have low serum PTH levels than in those with normal or moderately elevated levels, in association with low-turnover bone disease, this condition favors mineral deposition in vascular and other soft tissues instead of bone. Results from several studies, all of them reported an increase in CV mortality risk in patients with low PTH levels.

Nonetheless, consistent evidence associating Compare SHPT with low serum PTH levels which mortality rate is higher in patients undergoing dialysis is still lacking. so, in this prospective, observational clinical trial study. the investigators will observe the mortality and CV incidence rate between SHPT and low serum PTH levels. the investigators detect the iPTH levels of all the patients in the investigators' blood purification center. The patients whose iPTH are Less than 300pg/ml and more than the 800pg/ml are chosen to involve in this study. According to PTH levels The patients will be divided into two groups. Both two groups of patients will receive a reasonable treatment according to the suggestions in K/DOQI guidelines. Then, all of the patients will be followed for 24 months to compare the rate of cardiovascular and cerebrovascular events and mortality in each group.

Inclusion Criteria:

1. patients with age between 18-75 years.
2. patients in hemodialysis, whose iPTH is below 300pg/ml or above 800pg/ml.

Exclusion Criteria:

1. primary or tertiary hyperparathyroidism(hyperparathyroidism after kidney transplantation).
2. pregnant or lactating woman.
3. patients with severe liver disease and abnormal blood clotting mechanism.
4. patients with chronic wasting disease.
5. patients whose concurrent illnesses,disability,or geographical residence would hamper attendance at required study visit.

1. patients with age between 18-75 years.
2. patients in hemodialysis, whose iPTH is below 300pg/ml or above 800pg/ml.