Question

Which function of kidneys explains why hypocalcemia often develops in advanced kidney disease?

Group of answer choices

Renin production

Reabsorption of glucose

Activation of calcitriol

Mineral storage

EPO production

Answer 1

- Activation of calcitriol.

- Mineral storage.

Explanation:

- Hypocalcemia (low levels of calcium ions in the blood) in advanced kidney disease is mainly due to deceased production of calcitriol and electrolyte imbalance like hyperphosphatemia (increased levels of phosphate ions in the blood).

- Calcitriol (1,25 dihydroxy vitamin D3) is the active form of vitamin D3. It is synthesized in the kidneys by the conversion of 25-hyroxy vitamin D3 into 1,25 dihydroxy vitamin D3 in the proximal convoluted tubules of the nephrons of kidneys. Calcitriol helps in absorption of dietary calcium from the small intestines into the blood. It also helps in the reabsorption of calcium ions from the tubules of the kidneys thus reducing the excretion of calcium through urine.

- In advanced kidney disease, there is decreased synthesis of calcitriol in the kidneys which decreases the absorption of calcium from the small intestines as well as reduces the renal tubular reabsorption of calcium thus causes hypocalcemia.

- Normally, there is phosphate excretion through the kidneys but in advanced kidney disease phosphates are not excreted out which causes accumulation of phosphates leading to hyperphosphatemia. Phosphates inhibits calcium reabsorption in the kidneys. Thus, hyperphosphatemia due to advanced kidney diasease causes decreased reabsorption of calcium which leads to hypocalcemia.

Other options:

- Renin production is related to blood pressure regulation as renin causes production of angiotensin 2 and aldosterone. Angiotensin 2 helps in blood pressure regulation and aldosterone cuases sodium reabsorption from the tubules of the kidneys.

- Glucose has no direct effect on hypocalcemia. Altered glucose metabolism states like diabetes mellitus which causes sustained hyperglycemic can lead to advanced kidney diasease. Diabetes mellitus is one of the leading causes of advanced kidney diasease and renal failure.

- EPO (erythropoetin) is a hormone produced in the cells of proximal convoluted tubules of nephrons in the kidneys. It stimulates the process of erythropoesis (red blood cells production).