Final answer:
PTH and calcitonin regulate blood calcium levels, with PTH increasing levels by stimulating bone resorption, and calcitonin decreasing them by inhibiting osteoclast activity. Vitamin D, activated by PTH, is essential for calcium absorption from food, and inadequate intake of either nutrient can increase the risk of osteoporosis.
Step-by-step explanation:
The regulation of blood calcium levels involves several hormones, with parathyroid hormone (PTH) and calcitonin playing significant roles. Firstly, PTH is secreted by the parathyroid glands in response to low blood Ca2+ levels, leading to increased bone resorption by osteoclasts, enhanced calcium reabsorption in the kidneys, and elevated dietary calcium absorption in the intestines, partly through its role in activating vitamin D (calcitriol). Conversely, calcitonin, which is produced by the thyroid gland, generally acts to lower blood calcium levels by inhibiting osteoclasts and stimulating bone deposition.
Regarding vitamin D, it is indeed an essential component in the regulation of calcium since it aids in the absorption of calcium from food. Without sufficient vitamin D, the body cannot efficiently absorb dietary calcium, increasing the risk of calcium deficiency and potentially leading to issues like osteoporosis. Furthermore, a marginal intake of calcium can also increase the risk of developing osteoporosis, as inadequate calcium levels may lead to bone demineralization over time.