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progesterone (prōjĕsˈtərōnˌ), female sex hormone that induces secretory changes in the lining of the uterus essential for successful implantation of a fertilized egg. A steroid, progesterone is secreted chiefly by the corpus luteum, a group of cells formed in the ovary after the follicle ruptures during the release of the egg cell. If fertilization does not take place, the secretion of progesterone decreases and menstruation occurs. If fertilization does occur, progesterone is secreted during pregnancy by the placenta and acts to prevent spontaneous abortion; the hormone also prepares the mammary glands for milk production. Progesterone is also synthesized from cholesterol in the cortex of the adrenal gland where it is a precursor for the synthesis of other steroids including testosterone. Synthetic compounds with progesteronelike activity have been developed that, along with estrogen, are used in oral contraceptives.
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A steroid hormone produced in the corpus luteum and placenta. The hormone has an important physiological role in the luteal phase of the menstrual cycle and in the maintenance of pregnancy. In addition, progesterone produced in the testis and adrenals has a key role as an intermediate in the biosynthesis of androgens, estrogens, and the corticoids (adrenal cortex steroids). See Androgen, Cholesterol, Estrogen, Menstruation, Steroid, Sterol

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



in humans and vertebrate animals, a female sex hormone. Chemically, progesterone is a steroid that is synthesized in the body from cholesterol. It is an intermediate in the biosynthesis of all steroid hormones and can form in any tissues that secrete these hormones. Its structural formula is

In humans and higher animals, progesterone is primarily synthesized in the corpus luteum of the ovaries; the luteinizing hormone of the pituitary gland regulates its production. In the blood, progesterone mainly occurs in complexes with proteins.

By interacting with estriadol, another female hormone, progesterone regulates the estrous cycle in mammals and the menstrual cycle in humans. In the preovulatory phase of the sex and reproductive cycles in women, the daily production of progesterone occurs principally in the adrenal cortex and measures 1 to 3 mg. In the postovulatory phase, as much as 20 to 30 mg of progesterone are produced, principally in the corpus luteum. Progesterone produces changes in the uterine mucosa, which prepare the uterus for the implantation of the fertilized egg. When fertilization does not occur, the corpus luteum atrophies and the secretion of progesterone decreases. During a normal pregnancy, the placenta participates in the required daily production of as much as 200 to 250 mg of progesterone. Progesterone suppresses the activity of the smooth musculature of the uterus and thus prevents spontaneous abortion of the fetus; it also inhibits the ovulation of new follicles. The concentration of progesterone in the uterus decreases at the end of pregnancy, which serves as one of the trigger mechanisms of childbirth.

In medicine, progesterone and its synthetic derivatives (generally called progestins, or gestagens) are used to treat various disturbances of pregnancy and the ovarian cycle; they are also used in combination with estrogens as contraceptives. Derivatives of progesterone that act as repellents have been discovered in some insects. Flowering plants have also been found to produce progesterone.

In 1934, A. Butenandt contributed to the discovery of the chemical structure of progesterone.


Savchenko, O. N. Gormony iaichnika i gonadotropnye gormony. Leningrad, 1967.
Heftmann, E. M. Biokhimiia steroidov. Moscow, 1972. (Translated from English.)


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


C21H30O2 A steroid hormone produced in the corpus luteum, placenta, testes, and adrenals; plays an important physiological role in the luteal phase of the menstrual cycle and in the maintenance of pregnancy; it is an intermediate in the biosynthesis of androgens, estrogens, and the corticoids.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


a steroid hormone, secreted mainly by the corpus luteum in the ovary, that prepares and maintains the uterus for pregnancy. Formula: C21H30O2
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
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To determine which female hormone deficiencies and excesses are causing female-related disorders, and which hormone supplements to provide as a treatment, I recommend physicians train their skills in recognizing the differences in actions and deficiency signs and symptoms between estrogens and progesterone.