By disintegrating bone matrix, osteoclasts release calcium into the circulation. B parathyroid hormone is the correct answer. Calcium levels are regulated by parathyroid hormone, which acts on bone cells, the small intestine, and the kidneys. Parathyroid hormone increases renal reabsorption of calcium in the kidney and promotes entry of calcium into the bones to form new bone.
Osteoclasts are in charge of resorbing bone matrix and releasing essential minerals, such as calcium, back into the circulation. When blood calcium levels are low, they are boosted by parathyroid hormone. Osteoblasts construct bone matrix and then develop into osteocytes, which protect bone tissue.
Parathyroid hormone, in combination with calcitriol produced in the kidney under the effect of PTH, regulates calcium release from bone. Increase in serum calcium levels activates calcitonin which has a direct inhibitory effect on the parathyroid gland. Parathyroid hormone also plays an important role in regulating the amount of calcium that is absorbed by the intestine through the action of its receptor present on the surface of intestinal cells.
Calcium channels are proteins in cell membranes that control the flow of calcium into and out of cells. There are three main types of calcium channels: voltage-dependent, ligand-gated, and receptor-operated. Voltage-dependent calcium channels (VDCC) allow sodium ions to enter cells along with calcium ions. The voltage across the cell membrane is required for the channel to open. Once activated, VDCCs remain open for several seconds or minutes before closing. Ligand-gated calcium channels are sensitive to small molecules called neurotransmitters that are released from nerve terminals during synaptic transmission. When a neuron communicates with another neuron or with other cells within the body, it releases glutamate which opens these channels resulting in the influx of calcium. Receptor-operated calcium channels are located on the surface of some cells such as muscle cells where they regulate the contraction and relaxation of these cells.
When the serum calcium level drops, the parathyroid glands produce PTH into the blood, which instructs bone cells (osteoclasts) to release calcium from the bone surfaces. The osteoclasts then degrade the bone so that it can be replaced with new bone that will contain greater amounts of calcium.
The body also releases calcitonin during these changes in calcium balance. Calcitonins are a group of hormones that include salmon calcitonin which has been used successfully to prevent and treat pain caused by osteoporosis. Source: National Institute of Diabetes and Digestive and Kidney Diseases
Calcitonins inhibit the activity of osteoclasts and promote the absorption of calcium by the bones. Thus they reduce the amount of bone loss and increase the amount of bone formation. However, they do not appear to have any effect on the number of fractures due to osteoporosis. Source: Uptodate.com
When calcium levels in the blood are low, the parathyroid gland secretes parathyroid hormone. This hormone stimulates effector organs (the kidneys and bones). Calcium is not eliminated in the urine by the kidneys. Rather, it is reabsorbed from them into plasma vessels.
Calcium is an essential element for healthy bone growth. It plays a key role in bone matrix production and tissue mineralization. The body normally removes all of the calcium that it uses. However, if this process is exceeded, then the serum calcium level will decrease due to removal of excess calcium by the liver and storage as calbindin-D9K in the intestine and other tissues. Serum calcium levels can also be elevated when too much calcium enters the bloodstream which cannot be removed due to impaired renal function. In such cases, hypercalcemia results.
People with vitamin D deficiency may have higher rates of osteoporosis. Vitamin D helps your body absorb calcium. Therefore, people who do not produce enough vitamin D may need more calcium to protect against osteoporosis. Also, people who lose muscle mass when they become sick or older may have lower levels of calcidiol, the active form of vitamin D. They may need more calcium to build strong bones and reduce their risk of fracture.
High levels of calcium in the blood can cause kidney damage.