In humans, there are three calcium-regulating hormones that play crucial roles in regulating calcium levels in the body and maintaining healthy bones. These hormones are parathyroid hormone, calcitriol and calcitonin. Parathyroid hormone stimulates bone formation and resorption and maintains calcium levels in the body. Calcitriol, produced from vitamin D, encourages the intestines to absorb enough calcium and phosphorus and also has a direct effect on bones. Calcitonin is responsible for inhibiting bone breakdown and protecting the body from abnormally high levels of calcium.
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Paratormonio (PTH)
The parathyroid glands are four small glands located near the thyroid in the neck. They produce one of the human calcium-regulating hormones, parathyroid hormone (PTH), which precisely controls the level of calcium in the blood. The parathyroid glands are very sensitive to even small changes in the concentration of calcium in the blood and therefore play an important role in the process.calcium regulation. When a drop in blood calcium levels is detected, the parathyroid glands increase PTH secretion. PTH tells the kidneys to conserve calcium. It also stimulates the production of another hormone, calcitriol, which increases the absorption of calcium in the intestine. PTH also acts on the bones and increases the transfer of calcium from the bones to the blood.
Excessive secretion of PTH, one of the human calcium-regulating hormones, is known as hyperparathyroidism. Excess PTH, for example, from a parathyroid-secreting tumor, can lead to bone loss. In addition to bone resorption, PTH stimulates bone formation and makes bones stronger when the hormone is given intermittently in small amounts. Recent treatments ofosteoporosisare based on this characteristic of PTH.
Another hormone called PTH-related protein has recently been identified. Under normal circumstances, this hormone regulates bone and cartilage formation in the developing fetus. In people with certain types of cancer, a condition known as malignant hypercalcemia occurs due to overproduction of PTH-related protein, which acts like PTH and causes excessive bone breakdown and abnormally high levels of calcium in the blood.
Calcitriol
Also known as 1,25-dihydroxyvitamin D, this is one of the human calcium-regulating hormones. It is a derivative of vitamin D. Enzymes in the kidneys and liver produce this hormone, which affects many different tissues and organs. The main function of calcitriol is to increase the absorption of calcium and phosphorus from the intestine and make these minerals available to the skeleton. Vitamin D is not an essential dietary element and can be produced in the skin from cholesterol by exposure to ultraviolet light (sunlight); So it's not technically a vitamin. However, insufficient exposure to sunlight can lead to low levels of vitamin D, which must be supplemented through dietary sources.
The need for dietary vitamin D has increased recently. Deficiencies of this vitamin have become more common as people spend more time indoors and cover up outdoors to avoid sunburn. People who live in northern latitudes are particularly prone to vitamin D deficiency because the sun's rays are not strong enough in these parts of the world for the skin to produce enough vitamin D. Vitamin D is linked to calcium-regulating hormones in humans.
Lack of vitamin D in the body leads to poor bone mineralization and a condition known as rickets or osteomalacia (in children and adults respectively). Rickets is associated with bone pain and a characteristic bowing of the legs and other bony deformities. Osteomalacia is associated with an increased tendency to fracture. Vitamin D supplementation can restore bone calcium and reduce bone loss.
calcitonin
In addition to parathyroid hormone and calcitriol, calcitonin is the third human calcium-regulating hormone. It is produced in the thyroid gland (by cells other than those that produce thyroid hormones). Calcitonin inactivates osteoclasts and prevents bone breakdown. Calcitonin plays an important role in bone development and calcium regulation at a young age. In adults, the effects of this hormone are temporary. A very high or very low calcitonin level in an adult does not cause problems with blood calcium levels or bone strength. However, it is possible to use this hormone as a medicine to treat bone diseases.
sex hormones
In addition to the three hormones regulating calcium in humans - PTH, calcitriol and calcitonin - sex hormones such as estrogen and testosterone play important roles in regulating skeletal growth and maintaining bone mass and strength. Estrogen and testosterone affect bone health in both men and women. The increase in bone formation or growth spurt during puberty is supported by sex hormones. Cartilaginous plates at the ends of long bones elongate these bones, leading to the dramatic increase in height normally seen during puberty. By late adolescence, high concentrations of sex hormones lead to closure of the epiphyseal growth plates and replacement of cartilage by bone at these sites. This stops growth after puberty.
estrogen
Similar to calcium-regulating hormones in humans and their effects on the skeleton, estrogen stimulates the formation of new bone. It also acts on osteoclasts to inhibit bone loss at different stages of life. In women going through menopause, the level of estrogen in the body decreases significantly. This is why menopause is associated with a rapid loss of bone mass. Hormone replacement therapy (HRT) with exogenous estrogen is given to women going through menopause to prevent this age-related bone loss. However, the use of HRT is controversial because this therapy is associated with an increased risk of breast cancer, cardiovascular disease and blood clots.
Testosterone
Calcium-regulating hormones in humans affect bone through calcium regulation. Testosterone plays an important role in skeletal growth by acting directly on the bones. Testosterone also stimulates muscle growth, which puts pressure on the bones and thus stimulates bone formation. Fat cells convert testosterone to estrogen, allowing testosterone to serve as the body's source of estrogen. Estrogen is important for bone health in both men and women. In fact, circulating estrogen hormone levels are higher in older men than in older (postmenopausal) women.
Other hormones involved in bone health
growth hormones
In addition to the three human calcium-regulating hormones and sex hormones, other hormones also play an important role in regulating skeletal growth. One such hormone is growth hormone, which is produced by the pituitary gland in the brain. Growth hormone stimulates the liver to produce and release large amounts of insulin-like growth factor, or IGF-1, into the circulation. In addition to the liver, the hormone IGF-1 is also produced locally in bones and some other tissues, also under the regulation of growth hormone. Furthermore, growth hormone also has a direct effect on bone (unlike IGF-1).
The skeletal growth seen during puberty is accelerated by growth hormone. Inolder people, production of growth hormone and IGF-1 decreases, which is why the ability to replace resorbed bone or rapidly form new bone decreases with age. Although growth hormone and IGF-1 stimulate both bone formation and bone resorption, they act primarily on bone-forming cells, resulting in increased bone mass.
thyroid hormones
In addition to calcium-regulating hormones in humans, hormones produced by the thyroid affect bones because they increase the energy produced by all cells in the body, including bone cells. This increased energy production leads to increased bone formation and resorption. Lack of thyroid hormones in childhood leads to growth disorders. Abnormally high levels of thyroid hormones in the blood can lead to excessive bone loss and a weak skeleton. Additionally, it is believed that TSH, or thyrotropin, a pituitary hormone that regulates the production of thyroid hormones, can also directly affect bones.
cortisol
Cortisol, a hormone produced by the adrenal glands, is vital for regulating the body's metabolism. It plays a crucial role in the body's ability to handle injury and stress. The effects of cortisol on the skeleton are complex. Although small amounts of cortisol are necessary for normal bone development, when present in large amounts, cortisol blocks bone growth. Along with calcium-regulating hormones in humans, it is one of the hormones that affect bones.
Glucocorticoids (synthetic cortisol) are used to treat conditions such as arthritis and asthma. Prolonged use of these drugs can cause bone loss due to increased bone breakdown and decreased bone formation. Therefore, prolonged treatment with high doses of glucocorticoids can put a person at high risk of fracture.
Insulin
In addition to the calcium-regulating hormones mentioned above in humans, several other hormones circulating in the bloodstream also affect the skeleton. Insulin plays an important role in bone growth. In people with insulin deficiency, there is an impaired response to other factors that stimulate bone growth. Leptin, a recently discovered hormone produced by fat cells to regulate energy balance, is thought to affect the skeleton.
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