What happens in bone when blood calcium levels decrease when blood calcium levels increase?
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Calcium is an important mineral that our bodies need to keep us healthy. Having cancer can affect the amount of calcium in the body. Nearly all the calcium in the body is stored in bone tissue. A small amount circulates in our blood and other body fluids. There is also some inside our cells. We need calcium to: We need to get calcium from our diet. Foods which contain calcium include: The level of calcium in the blood is normally between 2.1 mmol per litre and 2.6 mmol per litre. But remember that blood levels can vary a little from person to person. You might need treatment if your calcium level goes above or below these levels. Our bodies absorb calcium from the food we eat through the lining of the bowel. The calcium is stored in our bones. The body controls the amount of calcium in the bloodstream very carefully. When blood levels of calcium fall too low, the bones release calcium into the blood. The amount of calcium the bowel absorbs from food increases and the kidneys get rid of less calcium through the urine. The opposite happens if blood levels of
calcium get too high. There are 3 hormones in the body that play an important role in keeping the correct balance of calcium in the blood. These are:
 Blood calcium levels that are too high or too low can cause serious problems. Having too much calcium in the blood is called hypercalcaemia. This is pronounced hyper-kal-seem-ia. Not having enough calcium is called hypocalcaemia. This is pronounced hypo-kal-seem-ia. The main causes of hypercalcaemia include:
A low calcium level is rare in people with cancer. The main causes of having a low level of calcium in the blood include:
Learning Outcomes
Hormonal Control of Blood Calcium LevelsRegulation of blood calcium concentrations is important for generation of muscle contractions and nerve impulses, which are electrically stimulated. If calcium levels get too high, membrane permeability to sodium decreases and membranes become less responsive. If calcium levels get too low, membrane permeability to sodium increases and convulsions or muscle spasms can result. Figure 1. Parathyroid hormone (PTH) is released in response to low blood calcium levels. It increases blood calcium levels by targeting the skeleton, the kidneys, and the intestine. (credit: modification of work by Mikael Häggström) Blood calcium levels are regulated by parathyroid hormone (PTH), which is produced by the parathyroid glands, as illustrated in Figure 1. PTH is released in response to low blood Ca2+ levels. PTH increases Ca2+ levels by targeting the skeleton, the kidneys, and the intestine. In the skeleton, PTH stimulates osteoclasts, which causes bone to be reabsorbed, releasing Ca2+ from bone into the blood. PTH also inhibits osteoblasts, reducing Ca2+ deposition in bone. In the intestines, PTH increases dietary CA2+ absorption, and in the kidneys, PTH stimulates reabsorption of the CA2+. While PTH acts directly on the kidneys to increase Ca2+ reabsorption, its effects on the intestine are indirect. PTH triggers the formation of calcitriol, an active form of vitamin D, which acts on the intestines to increase absorption of dietary calcium. PTH release is inhibited by rising blood calcium levels. Hyperparathyroidism results from an overproduction of parathyroid hormone. This results in excessive calcium being removed from bones and introduced into blood circulation, producing structural weakness of the bones, which can lead to deformation and fractures, plus nervous system impairment due to high blood calcium levels. Hypoparathyroidism, the underproduction of PTH, results in extremely low levels of blood calcium, which causes impaired muscle function and may result in tetany (severe sustained muscle contraction). The hormone calcitonin, which is produced by the parafollicular or C cells of the thyroid, has the opposite effect on blood calcium levels as does PTH. Calcitonin decreases blood calcium levels by inhibiting osteoclasts, stimulating osteoblasts, and stimulating calcium excretion by the kidneys. This results in calcium being added to the bones to promote structural integrity. Calcitonin is most important in children (when it stimulates bone growth), during pregnancy (when it reduces maternal bone loss), and during prolonged starvation (because it reduces bone mass loss). In healthy nonpregnant, unstarved adults, the role of calcitonin is unclear. Hormonal Regulation of GrowthHormonal regulation is required for the growth and replication of most cells in the body. Growth hormone (GH), produced by the anterior portion of the pituitary gland, accelerates the rate of protein synthesis, particularly in skeletal muscle and bones. Growth hormone has direct and indirect mechanisms of action. The first direct action of GH is stimulation of triglyceride breakdown (lipolysis) and release into the blood by adipocytes. This results in a switch by most tissues from utilizing glucose as an energy source to utilizing fatty acids. This process is called a glucose-sparing effect. In another direct mechanism, GH stimulates glycogen breakdown in the liver; the glycogen is then released into the blood as glucose. Blood glucose levels increase as most tissues are utilizing fatty acids instead of glucose for their energy needs. The GH mediated increase in blood glucose levels is called a diabetogenic effect because it is similar to the high blood glucose levels seen in diabetes mellitus. Figure 2. Growth hormone directly accelerates the rate of protein synthesis in skeletal muscle and bones. Insulin-like growth factor 1 (IGF-1) is activated by growth hormone and also allows formation of new proteins in muscle cells and bone. (credit: modification of work by Mikael Häggström) The indirect mechanism of GH action is mediated by insulin-like growth factors (IGFs) or somatomedins, which are a family of growth-promoting proteins produced by the liver, which stimulates tissue growth. IGFs stimulate the uptake of amino acids from the blood, allowing the formation of new proteins, particularly in skeletal muscle cells, cartilage cells, and other target cells, as shown in Figure 2. This is especially important after a meal, when glucose and amino acid concentration levels are high in the blood. GH levels are regulated by two hormones produced by the hypothalamus. GH release is stimulated by growth hormone-releasing hormone (GHRH) and is inhibited by growth hormone-inhibiting hormone (GHIH), also called somatostatin. A balanced production of growth hormone is critical for proper development. Underproduction of GH in adults does not appear to cause any abnormalities, but in children it can result in pituitary dwarfism, in which growth is reduced. Pituitary dwarfism is characterized by symmetric body formation. In some cases, individuals are under 30 inches in height. Oversecretion of growth hormone can lead to gigantism in children, causing excessive growth. In some documented cases, individuals can reach heights of over eight feet. In adults, excessive GH can lead to acromegaly, a condition in which there is enlargement of bones in the face, hands, and feet that are still capable of growth. Try ItContribute!Did you have an idea for improving this content? We’d love your input. Improve this pageLearn More What happens in bone when blood calcium levels increase?In most cases, the excess calcium in your blood was leached from your bones, which weakens them. This can cause bone pain and muscle weakness. Brain. Hypercalcemia can interfere with how your brain works, resulting in confusion, lethargy and fatigue.
What happens when the blood calcium level decreases?The calcium level in blood can be moderately low without causing any symptoms. If levels of calcium are low for long periods, people may develop dry scaly skin, brittle nails, and coarse hair. Muscle cramps involving the back and legs are common.
What increases blood calcium levels and decreases blood calcium levels?PTH also helps control the levels of phosphorus (a mineral) and vitamin D (a hormone) in your blood and bones. You have four pea-sized parathyroid glands located behind your thyroid gland. Whereas parathyroid hormone increases blood calcium levels, calcitonin decreases blood calcium levels.
What happens to bones when calcium is low?A lifelong lack of calcium plays a role in the development of osteoporosis. Low calcium intake contributes to diminished bone density, early bone loss and an increased risk of fractures. Eating disorders. Severely restricting food intake and being underweight weakens bone in both men and women.
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