The Effects of Vitamin D and Calcium Supplementation to Parathyroid Hormone in CHB Patients Treated With Tenofovir Disoproxil Fumarate

Hepatitis B virus is a global public health problem. This infection leads to chronic hepatitis, cirrhosis and liver cancer. According to past statistics, infection with hepatitis B virus is a common cause of hepatocellular carcinoma about 60% in East-Asia and Africa and about 20% in Western countries. About 350-400 million people are infected worldwide. Infection with hepatitis B virus is also an important factor of death in 1million patients per year.

Nucleot(s)ide is an antiviral drug that can reduce the number of viruses, reduce the risk of HCC, regress hepatic fibrosis and reduce death from Hepatitis B viral infection. Nowadays, the recommendation of nucleot(s)ide prefers Tenofovir disoproxil fumarate (TDF), Tenofovir Alafenamide (TAF) and Entecavir (ETV) than Lamivudine, Adefovir and Telbivudine due to high potency and low resistance rate Tenofovir disoproxil fumarate (TDF) is one of nucleotide analogue that inhibits reverse transcriptase in HBV replication process. However, long-term TDF therapy may have side effects especially nephrotoxicity. The proposed mechanisms of nephrotoxicity of TDF are cumulative of TDF at proximal tubule of kidney leads to mitochondrial toxicity, downregulation of sodium-phosphorus cotransporter, sodium/ hydrogen exchanger 3 and aquaporin 2, decreased endothelial nitric oxide-synthase (eNOS) and renal vasoconstriction results in tubulopathy in renal proximal tubule, increase of phosphate loss in urine and increase od serum creatinine.

Moreover, TDF also affects to decrease bone mineral density (BMD) that related with renal phosphate loss, loss of osteoblast function, high parathyroid hormone level regardless of vitamin D level and high fibroblast growth factor 23 (FGF23) leads to worsen in bone mineralization Vitamin D has a protective effect and indicate for osteoporosis treatment. The chronic hepatitis B infected patients with vitamin D deficiency may have a poor prognosis in hepatic fibrosis and high HBV DNA level. Previous studies in human immunodeficiency virus (HIV) infected patients who treated with TDF containing regimen antiretroviral therapy, in vitamin D supplement group had a statistic significance of low parathyroid hormone level and better in bone mineral density regardless of initial vitamin D level. Therefore, the main objective of this study is to evaluate the vitamin D and calcium supplement to patients with hepatitis B who have taken TDF, in parathyroid hormone level, bone mineral density, renal function and renal phosphate loss compared to patients who have no vitamin D and calcium supplement.