Definition of Pseudohypoparathyroidism:

Pseudohypoparathyroidism is a genetic disorder that is similar to hypoparathyroidism, but which results from the body's lack of response to parathyroid hormone rather than decreased production of the substance.

Causes, incidence, and risk factors:

The parathyroid glands help control calcium use and removal by the body. They do this by producing parathyroid hormone, or PTH. PTH helps control calcium, phosphorus, and vitamin D levels within the blood and bone.

Persons with pseudohypoparathyroidism produce the right amount of PTH, but the body is "resistant" to its effect. This causes low blood calcium levels and high blood phosphate levels.

Pseudohypoparathyroidism is caused by abnormal genes. All forms of pseudohypoparathyroidism are very rare.

Type Ia is inherited in an autosomal dominant manner. That means only one parent needs to pass you the defective gene in order for you to develop the condition. The condition causes short stature, round face, and short hand bones, and is also called Albright's hereditary osteodystrophy.

Type Ib involves resistance to PTH only in the kidneys. Type Ib is less understood than type Ia. Type II is very similar to type I in its clinical features, but the events that take place in the kidneys are different.

Type II pseudohypoparathyroidism also involves low blood calcium and high blood phosphate levels, but persons with this form do not develop the physical characteristics seen in those with Type Ia.

All forms of pseudohypoparathyroidism are very rare.