PTH abnormalities in chronic kidney disease

Uremic condition creates an oxidative stress environment which affects different organs of the body including skeletal system. Uremic toxins have inhibitory effects on osteoblasts and osteoclasts functions (۱,۲). A complex interaction among gut, kidney, bones and parathyroid glands involve in bone metabolism and calcium–phosphorous hemostasis. Parathyroid hormone (PTH), vitamin D and its receptors, fibroblast growth factor-۲۳ (FGF۲۳), and calcium-sensing receptors are different arms of this metabolic pathway (۳). With considering the critical role of kidneys in excretion of calcium and phosphate, thus abnormalities in bone turnover are inevitable in chronic kidney diseases (CKD) (۴).Hyperphosphatemia, hypocalcemia, deficiency of ۱, ۲۵(OH) vitamin D, skeletal resistance to vitamin D, and reduced expression of calcium sensing receptors all lead to secondary hyperparathyroidism in CKD patients (۵). Low serum ۲۵(OH) D level, which is a common finding (۸۰% of cases) in CKD (۶) - is an important factor in stimulating PTH secretion by parathyroid glands.Despite few data available about prevalence of low serum PTH levels in CKD, some new reports suggest occurrence of over suppression of PTH glands and hypoparathyroidism in CKD populations (۷-۹). A new study in a large population of adults with different stages of CKD reported low serum PTH in ۱۸% of cases with CKD stage ۵, with higher frequency in peritoneal dialysis patients (۳۱.۳%) (۷). High doses of vitamin D analogs and calcium‑based phosphate binders may induce over suppression of PTH release.An extended study by Akizawa et al (۸) involving ۸۱۸۸ hemodialysis and ۱۲۰۷ peritoneal dialysis patients treated in ۶۵ hospitals or clinics in Japan reported absolute (intact PTH levels <۶۰ pg/mL) and relative (intact PTH levels ۶۰-۱۶۰ pg/mL) hypoparathyroidism in ۳۱% and ۳۳.۴% of hemodialysis and ۳۱.۳% and ۳۱.۴% of peritoneal dialysis patients respectively. Naseri recently (۹) found hypoparathyroidism as a predominant PTH abnormality (۵۸.۷%) in children and young adults on dialysis. Thus, more attention to this aspect of parathyroid hormone abnormality is required.

کلیدواژه ها:

Fibroblast growth factor-۲۳ ، Chronic kidney disease ، Parathyroid hormone