Question

Parathyroid hormone

A. enhances the body's ability to retain calcium.
B. increases the body's rate of potassium excretion.
C. enables glucose to enter cells.
D. signals osteoblasts to release calcium from bones.

Answer 1

Parathyroid hormone primarily enhances the body's ability to retain calcium by increasing kidney reabsorption, stimulating osteoclasts to release calcium from bones, and promoting the synthesis of calcitriol for better absorption in the digestive tract.

Step-by-step explanation:

Parathyroid hormone (PTH) plays a crucial role in regulating calcium balance in the body. It is produced by the parathyroid glands in response to low levels of calcium in the blood. When calcium ion levels are low, PTH performs several functions to increase these levels:

1. It enhances reabsorption of calcium by the kidneys, reducing calcium excretion in the urine and increasing blood calcium levels.
2. PTH stimulates osteoclast activity which breaks down bone, releasing calcium into the bloodstream.
3. It stimulates the synthesis of calcitriol (active form of vitamin D) by the kidneys, which in turn enhances calcium absorption from the digestive tract.

Therefore, the correct answer is A, as PTH enhances the body's ability to retain calcium.