Question

Calcium plays a very important role in the formation of bones. Write on the role of endocrine glands and hormones responsible for maintaining calcium homeostasis.

Answer 1

Calcium homeostasis:

Homeostasis refers to the mechanisms present in a body that maintains the constant internal environment of the body. The concentration of calcium in the blood is maintained by two hormones: Parathyroid hormone and thyrocalcitonin.

Role of parathyroid hormone:

Parathyroid hormone released from the parathyroid glands plays a role in maintenance of calcium-phosphorus balance in the blood. It increases the calcium ions in the blood in the following ways:-

• Bone demineralisation: Stimulating the release of calcium from bones
• Absorption of calcium ions from the digested food
• Reabsorption of calcium ions from the renal tubules

Role of calcitonin:

Calcitonin is released in response to the increased level of $C{a}^{2+}$ ions in the blood. It is an antagonist of parathyroid hormone. It lowers the level of blood $C{a}^{2+}$ by the following ways:-

• Inhibiting the release of $C{a}^{2+}$ from the bones by limiting the activities of osteoclasts
• Limiting the absorption of calcium from the digested food after a certain level
• Increased excretion of calcium ions via urine

Antagonistic hormones:

Both calcitonin and parathyroid hormones act as antagonists in regulating blood calcium levels.