U- Shaped Association of Serum Parathyroid Hormone and Cognitive Dysfunction in Maintenance Haemodialysis Patients

Primary hypo- or hyperparathyroidism may present with cognitive dysfunction (CODY). Parathyroid disorders commonly occur in end-stage renal disease (ESRD) patients treated with maintenance haemodialysis (MHD) and may contribute to the accelerated cerebrovascular atherosclerotic calcification and neuropsychologic disorders prevalent in them. The relationship between serum intact parathyroid hormone (S.iPTH) and cognitive function in these patients remains to be fully explored.

Seventy-two stable ESRD patients (39 males, median age 50y) treated with thrice-weekly low-flux MHD for >6 months were tested by Montreal cognitive assessment-basic version (MoCA-B), geriatric depression scale- short form and pre-dialysis assessment of S.iPTH, vitamin D3, alkaline phosphatase, urea, creatinine, calcium, phosphorus and haemoglobin.

CODY and depression occurred in 51.4% and 65.3% of patients, respectively. A quadratic inverted U-shaped curve provided the best fit for the relation between S.iPTH and MoCA-B score (P=0.019). In the adjusted model, older age, lower haemoglobin, and higher S.iPTH predicted worse cognitive function.

CODY and depression are prevalent but largely unrecognized problems in older adult MHD patients. Short, easy-applicable neuropsychologic screening tests should help detection and management of these problems. Both markedly increased and relatively suppressed (but supranormal) S.iPTH levels are associated with CODY in them. This U-shaped association underscores the need to maintain some degree of secondary (adaptive) hyperparathyroidism. Calcium-based phosphorus binders and calcimimetics should be used cautiously in MHD patients to avoid overzealous suppression of PTH secretion which may disturb the bone-vascular axis and promote early vascular dementia. Large-scale prospective studies are needed to define the target S.iPTH range.