Hyperplasia is used to describe the body building extra cells in organs or tissue. This process can be completely normal, or at least not malignant, as in sebaceous hyperplasia, which causes skin cells to develop small yellow growths on the face. Perhaps the most benign form is the growth of the breasts during breastfeeding. Several forms of hyperplasia are a bit more complex, and may necessitate treatment. These include enlargement of the prostate, inflammation of the uterus, and congenital adrenal hyperplasia.

Congenital adrenal hyperplasia results from improper amounts of testosterone and estrogen, which cause marked differences in the development of sexual organs. These differences may be present either at birth or when children begin to develop secondary sexual characteristics. There are many different forms of congenital adrenal hyperplasia, but in overview, this disease can lead to malformed genitalia, ambiguous genitalia, early growth, early puberty or no onset of puberty, and infertility.

In the most serious form of congenital adrenal hyperplasia, the child has an abnormal 21st chromosome. This disease manifests immediately after birth, with nausea so severe that many children die by their second week of life. Supplementing or blocking certain hormones to produce natural growth and development of the sex organs can address less severe forms.

Inflammation of the uterus can be caused by hyperplasia of the endometrium, the lining of the uterus. This condition can be benign and cause no problems, but it may also be considered precancerous and require careful follow-up with a gynecologist. Several subtypes of hyperplasia of the endometrium exist.

Simple hyperplasia without atypia, or cystic hyperplasia, produces more cells in the endometrium, but does not change the cells. In moderate hyperplasia without atypia, the cells themselves have enlarged, but are still considered normal cells. These two types have about a 4% risk of developing into uterine cancer.

When simple or moderate hyperplasia presents with atypia, the cells that grow in the endometrium are not normal. In simple hyperplasia, the abnormal cells are not cancerous, but there is an 8% chance they will lead to uterine cancer. Moderate or complex hyperplasia is most indicated in causing uterine cancer, when cells are abnormal. About 25% of women with this type of hyperplasia will develop cancer.

Benign prostatic hyperplasia, or enlargement of the prostate, is non-cancerous. It can be uncomfortable, causing slowed urine stream, stopping and starting of urine, frequent need to urinate, or smaller than normal urine streams. Depending upon the severity of the condition, patients may be carefully monitored by doctors or given medications that help to shrink the prostate. In severe cases, surgery may be necessary.

Some enlargement of the prostate is expected in men as they age. Doctors generally examine the prostate to rule out prostate cancer. When there is no presence of cancer, the most common diagnosis is benign prostatic hyperplasia, which in most cases requires minimal if any treatment.