Vitamin D and the kidneys: a fascinating relationship

José Gilberto Henriques Vieira
J. Bras. Patol. Med. Lab. 2015;51(5):282-283
DOI:10.5935/1676-2444.20150045

ABSTRACT

Rocha and Andriolo(5) publish, in this number of Jornal Brasileiro de Patologia e Medicina Laboratorial (JBPML), interesting data on the biochemical profile of a group of Brazilian patients with end-stage renal disease in the pre-transplant period and three months after a successful procedure. Their very interesting findings confirm and stress several characteristics of this group of patients. First, normal renal function achieved after successful transplantation tends to normalize serum levels of phosphate and parathyroid hormone (PTH), even considering the short-time (three months) follow-up. Longer observation times may have shown lower PTH levels. Another very interest observation is their data on vitamin D: most of the patients, based on their 25(OH)D levels, were deficient pre- and post-transplant. Pre-transplant levels of 1,25(OH)2D are low due to the loss of 1-alpha-hydroxylase activity of renal tubular cells as well as the decline in glomerular filtration, since the delivery of precursor 25(OH)D depends on a complex megalin-associated vitamin D-binding protein transport(6). The finding of low 25(OH)D levels in most of the patients may not be surprising, because in the Brazilian population with normal renal function the incidence of vitamin D deficiency is more usual than it would be expected(7). As the authors point out, patients with end-stage renal disease have several other reasons to be vitamin D deficient. The implications of a low substrate in the deficiency of 1,25(OH)2D is an interesting point, especially when 25(OH)D is extremely low, as in one of the patients studied. The post-transplantation remarkable increase in 1,25(OH)2D levels denotes the recovery of normal renal function and is implicated in the tendency toward normalization of PTH function.Read more…