Importance of Recognizing Renal Tubular Disorders as a Cause of Bone Hypomineralization and Fractures in Adults.

Renal tubular disorders are often overlooked causes of acquired or inherited bone hypomineralization and fragility fractures in adults. The proximal tubule reabsorbs glucose, phosphate, low-molecular-weight proteins, amino acids, bicarbonate, and much of the sodium, potassium, chloride, and calcium. The distal nephron-the thick ascending limb of the loop of Henle, the distal convoluted tubule, and the collecting duct-regulates urine concentration and dilution, maintains acid-base balance via urinary proton secretion, and controls electrolytes, including sodium, potassium, magnesium, and calcium. Tubular defects may cause hyperphosphaturia (high urinary phosphate), hypercalciuria (high urinary calcium), or chronic metabolic acidosis (renal tubular acidosis, RTA). These changes weaken bone mineralization, disrupt bone turnover, and raise the risk of muscle weakness and fractures. This review summarizes acquired and genetic tubulopathies linked to hyperphosphaturia, hypercalciuria, and RTA and outlines a practical diagnostic approach for outpatients with bone fragility and suspected renal tubulopathy.