Influence of Serum Biochemistry on Bone and Kidney Phenotypes in Subjects With Symptomatic Primary Hyperparathyroidism

Abstract

OBJECTIVETo analyze the abnormalities in serum parathormone (PTH)-25-hydroxy-vitamin D (25-OHD) axis and calcium phosphate homeostasis in symptomatic PHPT patients having bone disease, nephrolithiasis and impaired renal function (IRF) at diagnosis. METHODSConsecutive adults (>18 years) with diagnosed symptomatic PHPT were enrolled in the retrospective study. Relevant clinical, biochemical and imaging parameters were recorded.RESULTSAdult patients with symptomatic PHPT were identified (N=60, age 45.2±14.4 years, 45 females). Predominant phenotypes were bone disease (osteoporosis and/or clinical fractures, n=42, 70%) and nephrolithiasis (n=24, 40%). Compared to patients with nephrolithiasis only (subgroup C, n=7) and simultaneous bone disease/nephrolithiasis (subgroup D, n=17), patients with isolated bone disease phenotype (subgroup B, n=25) had significantly higher alkaline phosphatase (AlP) and lower 25-OHD levels at presentation. Patient subgroups with nephrolithiasis had higher serum calcium levels and lower effective glomerular filtration rate (eGFR) at presentation. PTH was not significantly different among these subgroups. Patients with IRF (eGFR <60 ml/min per 1.73 m2, n=17) in our cohort had significantly higher serum calcium, phosphate, PTH levels and nephrolithiasis rates. Presence of nephrolithiasis, higher calcium x phosphate product (IRF: 36.2 ± 10.7 versus no IRF: 26.2 ± 5.7 mg2/dl2) and increased PTH levels were independently associated with IRF at diagnosis.CONCLUSIONSWhile PHPT patients with isolated bone disease were found to have lower 25-OHD and higher AlP levels independent of PTH levels; PTH was found to be an independent predictor of impaired renal function at diagnosis.