Is Parathyroid Hormone a Uremic Toxin?

Abstract

While there are many metabolic compounds that accumulate in uremic sera as a result of protein breakdown and the inability of the kidneys to excrete them, it is also evident that various hormonal imbalances occur in uremic animals and man. That one or more hormonal abnormalities may be the cause or major contributor to many of the manifestations of the uremic syndrome is plausible. One of the major hormonal imbalances in uremia is the elevation of the blood levels of parathyroid hormone (PTH). This is due to at least 2 factors. First, there is marked hyperplasia of the parathyroid glands in uremia, and as a consequence increased secretion of PTH. Second, the kidney is a major organ involved in the clearance and degradation of PTH; therefore, with the reduction in renal functioning mass, there would be greater accumulation of PTH and its fragments in blood for any given level of PTH secretion. Available data provide strong support for the notion that PTH is a major uremic toxin since many of the manifestations of the uremic syndrome may be related to or produced by the excess PTH in the blood of the uremic patients. The pertinent evidence for the hypothesis that PTH is a uremic toxin is reviewed.