|Melt. point||126°C (259°F)|
|Bioavailability||prolonged absorption, half-life approx 25-50 hours|
|Protein binding||96 percent-99 percent|
|Metabolism||hepatic to pregnanediols and pregnanolones|
|Half life||34.8-55.13 hours|
|Pregnancy cat.||B (USA)|
Progesterone is a steroid hormone in mammals that is involved in the female menstrual cycle, pregnancy (supporting gestation), and embryogenesis. The term progesterone also is used for natural or synthetic steroids that have a progesterone-like action on the body (Blakemore and Jennett 2001).
Progesterone belongs to a class of sex hormones called progestogens. Progesterone is the main progestogen produced in ovaries, particularly in the second half of the menstrual cycle after the occurrence of ovulation and the formation of a corpus luteum by the empty follicle (Blakemore and Jennett 2001). It is synthesized in the initial steps in the biosynthetic pathway involving the conversion of cholesterol to the sex steroids testosterone (an androgen) and estradiol (an estrogen), among others. It also is a precursor in the conversion to cortisol and aldosterone.
In addition to impacts on the reproductive system, progesterone also has impacts on the nervous system, immune system, skeletal system, thyroid function, and numerous other body functions. Human creativity has utilized natural progesterone and many synthetic analogues in many medical applications.
Progesterone is a steroid hormone. A steroid is any of a group of natural or synthetic, fat-soluble, organic compounds belonging to the class of lipids and characterized by a molecular core of four fused rings totaling 17 carbon atoms: Three six-carbon rings and one five-carbon ring fused together. The type of steroid is determined by the three-dimensional configuration and the type of additional side chains and rings.
Steroid hormones are steroids that act as hormones. Hormones are chemical messengers secreted by cells (including tissues and organs) in one part of a multicellular organism to travel to and coordinate the activities of different cells. An enormous range of chemicals are used for this type of cell-to-cell communication, including peptides (chains of amino acids) and steroids.
Progesterone is a type of progestogen, a subset of sex steroids, with androgens and estrogens being the other major sex steroids. Simply defined, progestogens (or progestagens) are a class of hormones that produce effects similar to progesterone. Progestoges that are synthetic are often referred to as progestins.
Like other steroids, progesterone consists of four interconnected cyclic hydrocarbons. Progesterone contains ketone and oxygenated functional groups, as well as two methyl branches. Like all steroid hormones, it is hydrophobic. This is mostly due to its lack of very polar functional groups. Progesterone has the chemical formula C21H30O2.
Progesterone was first isolated from hamster ovaries by Willard Myron Allen, who co-discovered it with his anatomy professor, George Washington Corner, at the University of Rochester Medical School. Allen first determined its melting point, molecular weight, and partial molecular structure. He also gave it the name Progesterone, derived from PROGEstational STERoidal ketONE. An avid mathematician, Allen recognized that the molecular weight of progesterone is 100 x π = 314 dalt.
Progesterone, like all other steroid hormones, is synthesized from pregnenolone, a derivative of cholesterol. This conversion takes place in two steps. The 3-hydroxyl group is converted to a keto group and the double bond is moved to C-4, from C-5.
Progesterone is the precursor of the mineralocorticoid aldosterone. Likewise, after conversion to 17-hydroxyprogesterone, another natural progestogen, it is a precursor of cortisol and androstenedione. Androstenedione can be converted to testosterone, an androgen, and to the estrogen's estrone, and estradiol.
In general, two sex hormones play a role in the control of the menstrual cycle in humans: Estradiol and progesterone. While estrogen peaks twice, during follicular growth and during the luteal phase, progesterone remains virtually absent prior to ovulation, but becomes critical in the luteal phase and during pregnancy. Many tests for ovulation check for the presence of progesterone.
Progesterone has been called "the hormone of pregnancy" because of its critical role in supporting the endometrium (uterine lining) and hence the survival of the conceptus (Bowen 2000). In humans, increasing amounts of progesterone are produced during pregnancy:
The placenta of all mammals produce progesterone but the quantity varies significantly (Bowen 2000). In some species, such as human, horses, sheep, and cats, sufficient progesterone is produced by the placenta that the ovaries and corpora lutea can be removed after establishment of the placenta without loss of the pregnancy (Bowen 2000). In others, such as cattle, pigs, goats, and dogs, luteal progesterone is essential throughout gestation because the placental secretions are not sufficient (Bowen 2000).
In general, levels are relatively low during the preovulatory phase of the menstrual cycle, rise after ovulation, and are elevated during the luteal phase. In women, progesterone levels tend to be less than 2 ng/ml prior to ovulation, and greater than 5 ng/ml after ovulation. If pregnancy occurs, progesterone levels are maintained at luteal levels initially. With the onset of the luteal-placental shift in progesterone support of the pregnancy levels start to rise further and may reach 100-200 ng/ml at term. Whether a decrease in progesterone levels is critical for the initiation of labor has been argued and may be species-specific. After delivery of the placenta and during lactation, progesterone levels are very low.
Progesterone levels are relatively low in children and postmenopausal women (NIH 2007). Adult males have levels similar to those in women during the follicular phase of the menstrual cycle.
Progesterone exerts its action primarily through the intracellular progesterone receptor, though a distinct, membrane bound progesterone receptor has recently been discovered.
It has a number of physiological effects, often regulatory, especially of the effects of estrogen. Estrogen often induces a multiplication of progesterone receptors.
Progesterone has many roles relating to the development of the fetus:
The fetus metabolizes placental progesterone in the production of adrenal mineralo- and glucosteroids.
Progesterone, like pregnenolone and dehydroepiandrosterone, belongs to the group of neurosteroids that are found in high concentrations in certain areas in the brain and are synthesized there.
Neurosteroids affect synaptic functioning, are neuroprotective, and affect myelinization (Schumacher et al. 2004). They are being investigated for their potential to improve memory and cognitive ability.
Progesterone as a neuroprotectant affects regulation of apoptotic genes.
Progesterone's effect as a neurosteroid works predominantly through the GSK-3 beta pathway, as an inhibitor. (Other GSK-3 beta inhibitors include bipolar mood stabilizers, lithium, and valproic acid.)
The use of progesterone and its analogues have many medical applications—both to address acute situations, and to address the long-term decline of natural progesterone levels. Because of the poor bioavailability of progesterone when taken orally, many synthetic progestins have been designed. However, the roles of progesterone may not be fulfilled by the synthetic progestins which in some cases were designed solely to mimic progesterone's uterine effects.
Progesterone is poorly absorbed by oral ingestion unless micronized and in oil, or with fatty foods; it does not dissolve in water. Products such as Prometrium, Uteregestan, Minagest, and Microgest are, therefore, capsules containing micronized progesterone in oil. Generally this is peanut oil, which may cause serious [allergy|[allergic reactions]] in some people, but compounding pharmacies, which have the facilities and licenses to make their own products, can use alternatives.
Vaginal and rectal application is also effective, with products such as CRINONE and PROCHIEVE bioadhesive progesterone vaginal gels (the only progesterone products FDA-approved for use in infertility and during pregnancy) and Cycff, which is progesterone in cocoa butter in the form of pessaries. Progesterone can be given by injection, but because it has a short half-life the injections need to be daily. Implants, for a longer period, are also available. Marketing of progesterone pharmaceutical products, country to country, varies considerably, with many countries having no oral progesterone products marketed, but they can usually be specially imported by pharmacies through international wholesalers.
"Natural progesterone" products derived from yams, do not require a prescription. Wild yams contain a plant steroid called diosgenin, which the human body cannot metabolize into progesterone. Diosgenin can only be chemically processed into progesterone in labs.
Note that oral birth control pills do not contain progesterone but a progestin.
Since most progesterone in males is created during testicular production of testosterone, and most in females by the ovaries, the shutting down (whether by natural or chemical means), or removal, of those inevitably causes a considerable reduction in progesterone levels. Previous concentration upon the role of progestagens (progesterone and molecules with similar effects) in female reproduction, when progesterone was simply considered a "female hormone," obscured the significance of progesterone elsewhere in both sexes.
The tendency for progesterone to have a regulatory effect, the presence of progesterone receptors in many types of body tissue, and the pattern of deterioration (or tumor formation) increasing in later years when progesterone levels have dropped, is prompting widespread research into the potential value of maintaining progesterone levels in both males and females.
|Hormones and endocrine glands - edit|
Hypothalamus: GnRH - TRH - CRH - GHRH - somatostatin - dopamine | Posterior pituitary: vasopressin - oxytocin | Anterior pituitary: GH - ACTH - TSH - LH - FSH - prolactin - MSH - endorphins - lipotropin
Thyroid: T3 and T4 - calcitonin | Parathyroid: PTH | Adrenal medulla: epinephrine - norepinephrine | Adrenal cortex: aldosterone - cortisol - DHEA | Pancreas: glucagon- insulin - somatostatin | Ovary: estradiol - progesterone - inhibin - activin | Testis: testosterone - AMH - inhibin | Pineal gland: melatonin | Kidney: renin - EPO - calcitriol - prostaglandin | Heart atrium: ANP
Adipose tissue: leptin, adiponectin
Target-derived NGF, BDNF, NT-3
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