How does the kidney handle calcium?
- Approximately 60% of the serum calcium is ionized or complexed and freely filtered by the glomerulus. The kidney reabsorbs 98% of the filtered calcium passively throughout the nephron.
- Sixty percent of the reabsorption occurs in the proximal convoluted tubule, 30% in Henle’s loop, and 10% in the distal tubule. Furosemide impairs calcium reabsorption in Henle’s loop and increases urinary calcium excretion.
- Thiazide diuretics impair distal tubule reabsorption of sodium, thereby increasing intracellular negativity and calcium reabsorption. Parathyroid hormone (PTH) increases distal tubular calcium reabsorption by enhancing calcium channel activity.
