Describe the causes and clinical importance of hyperplasia.

Hyperplasia is of two types:

A. Physiologic hyperplasia

B. Pathologic hyperplasia.

Physiologic hyperplasia:

Physiologic hyperplasia due to the action of hormones or growth factors occurs in several circumstances: when there is a need to increase functional capacity of hormone sensitive organs; when there is need for compensatory increase after damage or resection.

So physiologic hyperplasia may be

• Hormonal: proliferation of the glandular epithelium of the female breast at puberty and during pregnancy.
• Compensatory: Liver regeneration after donation of a lobe of liver.

Pathologic hyperplasia:

Most forms of pathologic hyperplasia are caused by excessive or inappropriate actions of hormones or growth factors acting on target cells.

1. Endometrial hyperplasia
2. Benign prostatic hyperplasia
3. Hyperplasia is a characteristic response to certain viral infections, such as papillomaviruses, which cause skin warts and several mucosal lesions composed of masses of hyperplastic epithelium.