How is calcium regulated in the body

Hyperparathyroidism results from an overproduction of PTH, which leads to excessive amounts of calcium being removed from bones and introduced into blood circulation. This may produce 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 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. Learning Objectives Explain how blood calcium levels are regulated by parathyroid hormone. Key Points The parathyroid hormone PTH , secreted by the parathyroid glands, is responsible for regulating blood calcium levels; it is released whenever blood calcium levels are low.

When blood levels of calcium get too high, the thyroid gland is stimulated to release calcitonin Figure 6. All of these actions lower blood levels of calcium. When blood calcium levels return to normal, the thyroid gland stops secreting calcitonin.

Calcium homeostasis, i. Hypocalcemia can result in problems with blood coagulation, muscle contraction, nerve functioning, and bone strength. Hypercalcemia can result in lethargy, sluggish reflexes, constipation and loss of appetite, confusion, and coma. Calcium homeostasis is controlled by PTH, vitamin D, and calcitonin and the interactions of the skeletal, endocrine, digestive, and urinary systems.

An individual with very low levels of vitamin D presents themselves to you complaining of seemingly fragile bones. Explain how these might be connected. Describe the effects caused when the parathyroid gland fails to respond to calcium bound to its receptors. Skip to content Learning Objectives By the end of this section, you will be able to: Describe the effect of too much or too little calcium on the body Explain the process of calcium homeostasis.

Chapter Review Calcium homeostasis, i. Review Questions. Critical Thinking Questions 1. To maintain a normal level of calcium in blood without weakening the bones, people need to consume at least 1, to 1, milligrams of calcium a day.

The level of calcium in blood is regulated primarily by two hormones:. The two halves lobes of the gland are connected When the calcium level in blood decreases, the parathyroid glands produce more parathyroid hormone.

When the calcium level in blood increases, the parathyroid glands produce less hormone. Parathyroid hormone does the following:.

Stimulates bones to release calcium into blood. Causes the kidneys to excrete less calcium in urine. Stimulates the digestive tract to absorb more calcium. Causes the kidneys to activate vitamin D , which enables the digestive tract to absorb more calcium. Calcitonin is produced by cells of the thyroid gland. It lowers the calcium level in blood by slowing the breakdown of bone, but only slightly. Too little calcium in the blood is called hypocalcemia Hypocalcemia Low Level of Calcium in the Blood In hypocalcemia, the calcium level in blood is too low.

A low calcium level may result from a problem with the parathyroid glands, as well as from diet, kidney disorders, or certain drugs. Too much calcium in the blood is called hypercalcemia Hypercalcemia High Level of Calcium in the Blood In hypercalcemia, the level of calcium in blood is too high.