pronucleus A cell nucleus with a haploid (halved) set of chromosomes—23 chromosomes in humans—that results from division (meiosis) of a germ cell. The male pronucleus is the sperm nucleus after it has entered the ovum at fertilization but before fusion with the female pronucleus. Similarly, the female pronucleus is the nucleus of the ovum before…
pronator foot type A type of foot that rolls far inward during the weight-bearing phase of the stride. This type of foot is characterized by a very low or flat arch. Heavier people often have feet of this type.
promoter In molecular biology, a site on DNA to which the enzyme RNA polymerase can bind to initiate the transcription of DNA into RNA.
prominent vertebra The seventh cervical (neck) vertebra, which has a long spinous process that projects out from the back of its vertebral body.
prolactinoma A benign tumor (called an adenoma) of the pituitary gland. Prolactinomas produce an excessive amount of the hormone prolactin. Prolactinomas are the most common type of pituitary tumor. Symptoms of prolactinoma are caused by pressure of the tumor on surrounding tissues or by excessive prolactin in the blood (hyperprolactinemia). Treatment may involve medications and/or…
prolactin A hormone secreted by the pituitary gland that stimulates lactation (milk production). It also has many other functions, including essential roles in the maintenance of the immune system. Abnormally high prolactin can delay puberty, interfere with ovulation in women, decrease libido in men, and decrease fertility. Elevated prolactin (hyperprolactinemia) may be due to a…
prokaryote An organism whose cells lack a discrete nucleus and other special subcellular compartments. Bacteria and viruses are prokaryotes. Humans are not prokaryotes, but rather eukaryotes.
progressive Increasing in scope or severity, advancing, or going forward. For example, a disease that is progressive is worsening.
prognostic Pertaining to the prognosis, the outlook for the patient.
prognosis The forecast of the probable outcome or course of a disease; the patient’s chance of recovery.
prognathism An overly prominent jaw. Prognathism may cause no problems or be associated with dental problems. Prognathism is characteristic of some diseases, such as acromegaly.
progestin Any one of a group of steroid hormones that have the effect of progesterone. See also progesterone.