The kidneys are paired organs that filter blood to remove metabolic waste products, regulate fluid and electrolyte balance, maintain acid-base homeostasis, and produce hormones including erythropoietin and active vitamin D. They process approximately 180 liters of filtrate daily, reabsorbing 99% while excreting 1-2 liters as urine.
Kidneys filter blood through nephrons (glomerulus → proximal tubule → loop of Henle → distal tubule → collecting duct), selectively reabsorbing water, electrolytes, glucose, and amino acids while excreting urea, creatinine, uric acid, and excess ions. They regulate calcium reabsorption in response to PTH, activate vitamin D to calcitriol, produce erythropoietin in response to hypoxia, and regulate blood pressure via the renin-angiotensin-aldosterone system. They also excrete ammonia from protein metabolism and maintain pH by excreting H+ or HCO3-.
Kidney dysfunction is common in metabolic syndrome, diabetes, and chronic inflammation. Kidneys are vulnerable to oxidative stress, AGEs, and inflammatory cytokines. Chronic low-grade inflammation can lead to glomerular damage and progressive loss of function. Kidney health is critical for detoxification, blood pressure regulation, and mineral homeostasis. Support includes adequate hydration, reduction of acid load, management of blood sugar and blood pressure, and reduction of nephrotoxic substances.
- Filter 180 liters of blood daily, producing 1-2 liters of urine
- Show median 100-150 Y+ (fetal) cells in microchimerism studies
- PTH stimulates calcium reabsorption in the kidney
- Activate vitamin D to calcitriol (1,25-dihydroxyvitamin D)
- Produce erythropoietin in response to hypoxia to stimulate red blood cell production
- Excrete ammonia from protein metabolism and maintain acid-base balance
- Can be damaged by chronic inflammation, oxidative stress, AGEs, and metabolic toxins
- Reduced cell number in liver, kidney, and pancreas occurs with fetal glucocorticoid exposure
- Parathyroid hormone — PTH stimulates calcium reabsorption in kidney tubules
- Calcium — kidneys reabsorb calcium from filtrate in response to PTH
- Vitamin D — kidneys convert 25-OH vitamin D to active calcitriol (1,25-OH2 D)
- erythropoietin — kidneys produce EPO in response to hypoxia
- renin — kidneys secrete renin to regulate blood pressure and fluid balance
- ammonia — kidneys excrete ammonia from protein metabolism
- urea — kidneys filter and excrete urea as the primary nitrogen waste product
- pH regulation — kidneys maintain acid-base balance by excreting H+ or HCO3-
- Type 2 Diabetes — diabetes causes diabetic nephropathy and progressive kidney damage
- AGEs — advanced glycation end-products accumulate in and damage kidney tissue
- chronic inflammation — chronic inflammation drives glomerular damage and kidney disease
- Liver — works with liver in detoxification; both organs vulnerable to metabolic stress
- pancreas — liver, kidney, and pancreas all show reduced size with fetal glucocorticoid exposure
- metabolic syndrome — metabolic syndrome increases risk of chronic kidney disease
- hypertension — kidneys regulate blood pressure via RAAS; hypertension damages kidneys
- Microchimerism — kidneys contain detectable fetal cells (Y+ cells) from pregnancy
- blood-brain barrier — unlike brain, kidneys are highly permeable and vulnerable to bloodborne toxins
- Cortisol — fetal cortisol exposure reduces kidney development and cell number
- oxidative stress — kidneys are vulnerable to oxidative damage from high metabolic activity
- dehydration — kidneys concentrate urine to conserve water during dehydration
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