A kidney tubule disease in which cells of the DCT had fewer receptors for parathyroid hormone might cause: Calcification of soft tissues Hypercalcemia Hypocalcemia Parathyroid glands to secrete less PTH Decreased calcium excretion through urine
The correct answer and explanation is:
Correct Answer: Hypocalcemia
In a kidney tubule disease where the distal convoluted tubule (DCT) cells have fewer receptors for parathyroid hormone (PTH), the body would struggle to maintain normal calcium levels. PTH plays a vital role in regulating calcium by acting on bones, kidneys, and the intestines. In the kidneys, especially in the DCT, PTH promotes calcium reabsorption back into the bloodstream. When PTH binds to its receptors on DCT cells, it triggers a series of events that increase calcium channels and transporters, enhancing calcium uptake and reducing calcium lost in the urine.
If the DCT cells have fewer receptors for PTH, this response is weakened. As a result, the kidneys would fail to reabsorb enough calcium from the filtrate, and more calcium would be excreted in the urine. This loss of calcium leads to a decrease in the amount of calcium in the blood, a condition known as hypocalcemia.
Hypocalcemia can cause a range of symptoms such as muscle cramps, tingling in the fingers, and even cardiac issues if not corrected. The body responds to low calcium levels by increasing the secretion of PTH in an effort to restore balance. However, if the receptors are not functioning properly, even high levels of PTH cannot correct the problem through kidney action alone.
Other options like hypercalcemia or decreased calcium excretion through urine do not occur in this condition because the defect lies in the kidney’s inability to respond to PTH, not in overactivity. The parathyroid glands would not secrete less PTH in this situation; rather, they might secrete more in response to the falling calcium levels. Therefore, hypocalcemia is the most accurate consequence of having fewer PTH receptors in the DCT.