Hyperplasia

Hyperplasia (or "hypergenesis") is a general term for an increase in the number of the cells of an organ or tissue causing it to increase in size. It may be due to any number of causes including (but not limited to) increased demand, chronic inflammatory response, hormonal dysfunctions, or neoplasia.

Hyperplasia may be harmless and occur as a result of increased demand on a particular tissue. An example of this would be when the breast starts to lactate as a response to pregnancy, when the cells divide and increase in number in order to be prepared for breastfeeding.

Hyperplasia may also be induced artificially by injecting hormones such as IGF-1 and human growth hormone. Perhaps the most interesting and potent effect IGF has on the human body is its ability to cause hyperplasia, which is an actual splitting of cells. Hypertrophy is what occurs during weight training and steroid use and is simply an increase in the size of muscle cells. With IGF use, one is able to cause this hyperplasia which actually increases the number of muscle cells present in the tissue. Weight training and, more dangerously, anabolic steroid use enables these new cells to mature in size and strength. In addition, animal tests have shown that stretching a muscle can trigger hyperplasia though this phenomenon has yet to be confirmed in humans.

Hyperplasia may also occur abnormally, and is associated with a variety of clinical diseases.

Some of the more commonly-known clinical forms of hyperplasia, or conditions leading to hyperplasia, are:

• Congenital adrenal hyperplasia.
• Polycystic ovary syndrome. The amenorrhea/oligomenorrhea associated with this syndrome results in hyperplasia of the endometrium, or inner lining of the uterus. If left untreated, this can lead to endometrial cancer. Hyperestrinism produces the glandular and stromal proliferation in endometrium. There are three types of endometrial hyperplasia: simple hyperplasia (cystic hyperplasia), adenomatous (complex) hyperplasia and atypical adenomatous (complex atypical) hyperplasia. These types are associated with variable risk of malignant change. To the naked-eye, the endometrium is thicker. Under the microscope, in simple hyperplasia, the proliferated epithelium is normal-appearing (columnar, unistratified or cuboidal, if the glands are cystic-dilated - cystic "Swiss cheese" hyperplasia) 1. This type has no increased risk of malignancy. The complex hyperplasia is characterized by crowded and irregular glands. There is a low risk of malignant transformation (10%). Complex atypical hyperplasia of endometrium, also called intraendometrial neoplasia, presents architectural and cytological atypia in a reduced stroma. There is a higher risk of malignant transformation (about 25% after three years).
• Benign prostatic hyperplasia, also known as prostate enlargement.
• Hyperplasia of the breast. Types of breast hyperplasia are:
  • benign ductal or lobular hyperplasia - increased growth in size and/or number of cells in breast ducts or lobes, but generally does not indicate an increased risk of breast cancer
  • atypical ductal or lobular hyperplasia - increased growth in size and/or number of cells in breast ducts or lobes that develops in an unusual pattern, and can indicate an increased risk of breast cancer. A regular follow-up program is recommended.
  • lobular carcinoma in situ, or LCIS - a form of atypical lobular hyperplasia where the cell changes in the lobes are very unusual. It presents a risk of breast cancer in the future. A regular follow-up program is highly recommended; also, a specialist may wish to discuss the option of surgery with a woman having this form of breast hyperplasia.
• Focal epithelial hyperplasia (also known as Heck's disease). This is a wart-like growth in the mucous tissues of the mouth or, rarely, throat that is caused by certain sub-types of the human papillomavirus (HPV). Heck's disease has not been known to cause cancer.
• Sebaceous hyperplasia - a condition where small yellowish growths develop on the skin, usually on the face. This condition is neither contagious nor dangerous.