Glossary

Paracrine
A cell's signaling of other cells by secreting a chemical that interacts with the receptors on nearby cells.
Parathyroid Glands
Small endocrine glands in the neck whose sole function is to regulate the body's calcium level for the proper functioning of the nervous and muscular systems.
Parathyroid Hormone (PTH)
Hormone secreted by the parathyroid glands and the most important endocrine regulator of calcium and phosphorus concentration in extracellular fluid.
Paricalcitol
19-nor-1, 25-dihydroxyvitamin D2. A noncalcemic vitamin D analogue that is used in the treatment of secondary hyperparathyroidism.
Parkinson's Disease (PD)
Motor system disorder which results from the loss of dopamine-producing brain cells.
Peptide hormone
Hormone belonging to a class of peptides that are secreted into the blood stream and have endocrine functions in living animals.
Peptides
Family of short molecules formed from the linking of various α-amino acids.
Peripheral Nervous System (PNS)
Contains only nerves, connects the Central Nervous System (brain and spinal cord) to the rest of the body. Composed of two major subdivisions: the Somatic Nervous System and Autonomic Nervous System.
Pharmacological dose
The minimum dose needed to make a drug medically effective in treating an illness.
Pharmacology
The scientific study of drugs and their effects, especially in the treatment of disease.
Phosphorus
Mineral macronutrient essential to all lifeforms. Phosphorus has a role in many bodily functions such as intracellular energy transfer, regulation of many biochemical processes, catalytic activity of enzymes, and oxygen dissociation from hemoglobin. The backbones of DNA and RNA are composed of phosphorus bound to sugars.
Physiological dose
The minimum dose needed to produce a physiological effect in the body.
Physiology
The normal mechanical, physical, and biochemical processes of living things.
Pituitary gland
An endocrine gland that is composed of two distinct parts: the anterior and posterior pituitary. Together these two parts secrete a battery of hormones that influence all cells and affect all physiologic processes within the body.
Pleomorphic
Occurring in various distinct forms, multi-functional.
Polychlorinated Biphenyls (PCBs)
Organic compounds that have been shown to be carcinogenic, adversely impacting the environment and human health. Although a ban was placed on their production in the 1970s, PCBs are still present in the environment.
Polymorphism
A small genetic change, or variation, that can occur within a person's DNA sequence.
Prehormone
A glandular secretory product that is a precursor of a hormone but has little or no inherent biological potency itself.
Prime
The Prospective Epidemiological Study of Myocardial Infarction.
Prodifferentiation
The process of cell maturation and self-definition through the acquisition of additional individual characteristics.
Prohormone
Any substance that can be converted to a hormone.
Prolactin (PRL)
Peptide hormone primarily associated with lactation.
Prostate-specific antigen (PSA)
A protein produced by normal prostate cells that plays an important role in fertility.
Proteolysis
Digestion of proteins by cellular enzymes (called proteases) or by intramolecular digestion.
PubMed
PubMed is a service of the U.S. National Library of Medicine that includes over 16 million citations from Medline and other life science journals for biomedical articles dating back to the 1950s.