Hyperparathyroidism
The parathyroid glands are four small glands located in the neck which produce parathyroid hormone, a hormone involved in the regulation of calcium and phosphate levels. Overactivity of one or more of the glands results in excessive parathyroid hormone production.
Hyperparathyroidism may be:

• primary - caused by problems in the glands themselves and leads to high levels of calcium in the blood (hypercalcaemia) or
• secondary - caused by low levels of calcium in the body.

Paget's Disease In this condition the normal bone remodelling process, in which new bone tissue gradually replaces older bone tissue, becomes disrupted. The new bone formed may become weak and misshapen, leading to pain and increased risk of fractures.