The goal of this observational study or clinical trial is to learn about the effect of neutrophil gelatinase-associated lipocalin (NGAL) on vascular calcification in maintenance hemodialysis patients with secondary hyperparathyroidism (SHPT). The main question it aims to answer is: the predictive effects of blood NGAL level on the efficacy of palicalcitol in the treatment of SHPT and the adverse reactions of vascular calcification progression. Participants will be treated with palicalcitol, followed up and undergo routine series of Chronic Kidney Disease-Mineral and Bone Disorder associated tests before and after treatment.

1. Sample size calculation: Because there was no previous study on the change of blood NGAL level in MHD patients with palicalcitol; refer to the NGAL changes before and after parathyroidectomy :N=12 NGAL715.84(578.73, 988.14)ng/mL before and 688.42(660.00, 760.26)ng/mL 4-7 days after surgery (p=0.071, paired T-test). According to the 20% loss rate; The sample size is finally determined to be 80 cases.
2. Patients: maintenance hemodialysis patients with secondary hyperparathyroidism (SHPT).
3. Palicalcitol injection
4. Follow-up The patients are followed up for 1 year.
5. Statistical methods All statistical tests are conducted by two-sided test, and the first type of error is 0.05 (α value) to determine the statistical significance of the difference. Quantitative data includ efficacy, laboratory test indicators, such as the number of cases, mean, median, standard deviation and range description. Qualitative data includ comorbidities, described in terms of frequency, composition or percentage. Statistical test: The parameter test method is preferred. If the data distribution differs greatly from the requirements of testing the hypothesis, the non-parameter test method will be used. Patients will be divided into two groups according to circulating NGAL levels before treatment; the clinical characteristics, changes of NGAL level, the efficacy of palicalcitol (changes of iPTH) and the main adverse reactions (increased blood calcium and phosphorus, progress of vascular calcification) are compared between two groups. T test or rank sum test are used for difference test. The correlation between blood NGAL level, VC score and CKD-MBD assay indexes is analyzed by pair-wise correlation and logistic multivariate regression.

Inclusion criteria:

• Chronic kidney disease (CKD) maintenance hemodialysis patients with secondary hyperparathyroidism (SHPT), iPTH>300pg/ml
• Age 18-65 years old
• Haven't used anti-PTH agents within 3 months
• Signed informed consent

Exclusion criteria:

• Allergic to vitamin D or similar drugs
• Vitamin D poisoning
• Expected survival is less than one year
• Acute inflammations, active liver disease, tumor, hospitalization within 3 months
• Fractures, major trauma or operations within 3 months.