Endocrine Abstracts

Hypophosphataemia is a common mineral metabolic abnormality affecting 2-3% of all hospital in patients and up to 34% of ICU patients. The causes are numerous. Over the last two decades following the identification of Fibroblast growth factor-23 (FGF-23) as the phosphaturic hormone responsible for Autosomal Dominant Hypophosphataemic Rickets (ADHR) in 2000 there has been an explosion in the understanding of phosphate homeostatic physiology and disorders of phosphate homeostasis. In this brief presentation I will provide an overview of hypophosphataemia, a structured approach to considering the causes of hypophosphataemia, review the physiology of phosphate homeostasis and go through a suggested approach to the investigation of this problem. I also aim to demystify the tubular maximum reabsorption of phosphate (TmP) / GFR test including a, hopefully fairly simple, description of the TmP/GFR test, when and how to perform it and how to interpret it. Finally, I will cover specific situations such as measuring FGF-23 in renal failure and the merits of using the C terminal vs the intact FGF-23 assays.