Parathyroid gland are two pairs of pea shaped organs in human body. The parathyroid hormone secreted  by this gland is essential for regulating calcium and phosphate balancing in blood. This hormone prevents the collagen synthesis and bone resorption. The malfunctioning of parathyroid gland causes hypoparathyroidism and hyperparathyroidism.

Hypoparathyrodism

This is due to the hypo secretion of parathyroid hormone . this is occurs due to the damage of parathyroids .this is will leads to the deficiency of calcium ions in blood. This will affect the depolarization of neurons .this will leads to difficulty in muscle movements .this situation is also named as hypocalcaemic tetany.

Hyperparathyroidism

This is due to the hyper secretion of parathyroid hormone. The blood calcium ions increased. That is the re absorption of calcium ions from bones increased. This will weakens the bones and it easily fractured. Due to de-mineralization the bone many deformed. In severe cases it is known as osteitis fibrosa cystica. This is a situation , the destroyed bones are replaced by cavities that contain fibrous tissue.