N
Nipple-sparing mastectomy
A procedure used to treat breast cancer in which the breast tissue is removed while the skin over the breast and the nipple are spared; an option used only when the breast tissue beneath the nipple and areola are free of cancer cells.
Nitric oxide
A colorless toxic gas formed by the oxidation of nitrogen; often used in medications to treat erectile dysfunction and other conditions because of its chemical signaling functions.
Nocturia
Excessive nighttime urination.
Non-obstructive coronary artery disease
A heart disease in which a coronary artery is obstructed by less than 50 percent.
Non-scalpel vasectomy
A minimally invasive vasectomy in which a surgeon cuts and seals the tubes that transport sperm cells during ejaculation without making an incision.
Non-seminoma tumor
A type of cancer that begins in cells that form sperm or eggs.