Progestins: Compounds that interact with PROGESTERONE RECEPTORS in target tissues to bring about the effects similar to those of PROGESTERONE. Primary actions of progestins, including natural and synthetic steroids, are on the UTERUS and the MAMMARY GLAND in preparation for and in maintenance of PREGNANCY.Progesterone Congeners: Steroidal compounds related to PROGESTERONE, the major mammalian progestational hormone. Progesterone congeners include important progesterone precursors in the biosynthetic pathways, metabolites, derivatives, and synthetic steroids with progestational activities.Promegestone: A synthetic progestin which is useful for the study of progestin distribution and progestin tissue receptors, as it is not bound by transcortin and binds to progesterone receptors with a higher association constant than progesterone.Medroxyprogesterone Acetate: A synthetic progestin that is derived from 17-hydroxyprogesterone. It is a long-acting contraceptive that is effective both orally or by intramuscular injection and has also been used to treat breast and endometrial neoplasms.Norethindrone: A synthetic progestational hormone with actions similar to those of PROGESTERONE but functioning as a more potent inhibitor of ovulation. It has weak estrogenic and androgenic properties. The hormone has been used in treating amenorrhea, functional uterine bleeding, endometriosis, and for contraception.Estrogen Replacement Therapy: The use of hormonal agents with estrogen-like activity in postmenopausal or other estrogen-deficient women to alleviate effects of hormone deficiency, such as vasomotor symptoms, DYSPAREUNIA, and progressive development of OSTEOPOROSIS. This may also include the use of progestational agents in combination therapy.Receptors, Progesterone: Specific proteins found in or on cells of progesterone target tissues that specifically combine with progesterone. The cytosol progesterone-receptor complex then associates with the nucleic acids to initiate protein synthesis. There are two kinds of progesterone receptors, A and B. Both are induced by estrogen and have short half-lives.Medroxyprogesterone: (6 alpha)-17-Hydroxy-6-methylpregn-4-ene-3,20-dione. A synthetic progestational hormone used in veterinary practice as an estrus regulator.Norgestrel: A synthetic progestational agent with actions similar to those of PROGESTERONE. This racemic or (+-)-form has about half the potency of the levo form (LEVONORGESTREL). Norgestrel is used as a contraceptive, ovulation inhibitor, and for the control of menstrual disorders and endometriosis.Norpregnadienes: Pregnadienes which have undergone ring contractions or are lacking carbon-18 or carbon-19.Norprogesterones: Progesterones which have undergone ring contraction or which are lacking carbon 18 or 19.Levonorgestrel: A synthetic progestational hormone with actions similar to those of PROGESTERONE and about twice as potent as its racemic or (+-)-isomer (NORGESTREL). It is used for contraception, control of menstrual disorders, and treatment of endometriosis.Estrogens, Conjugated (USP): A pharmaceutical preparation containing a mixture of water-soluble, conjugated estrogens derived wholly or in part from URINE of pregnant mares or synthetically from ESTRONE and EQUILIN. It contains a sodium-salt mixture of estrone sulfate (52-62%) and equilin sulfate (22-30%) with a total of the two between 80-88%. Other concomitant conjugates include 17-alpha-dihydroequilin, 17-alpha-estradiol, and 17-beta-dihydroequilin. The potency of the preparation is expressed in terms of an equivalent quantity of sodium estrone sulfate.Progesterone: The major progestational steroid that is secreted primarily by the CORPUS LUTEUM and the PLACENTA. Progesterone acts on the UTERUS, the MAMMARY GLANDS and the BRAIN. It is required in EMBRYO IMPLANTATION; PREGNANCY maintenance, and the development of mammary tissue for MILK production. Progesterone, converted from PREGNENOLONE, also serves as an intermediate in the biosynthesis of GONADAL STEROID HORMONES and adrenal CORTICOSTEROIDS.Pregnenediones: Unsaturated pregnane derivatives containing two keto groups on side chains or ring structures.Estrogens: Compounds that interact with ESTROGEN RECEPTORS in target tissues to bring about the effects similar to those of ESTRADIOL. Estrogens stimulate the female reproductive organs, and the development of secondary female SEX CHARACTERISTICS. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds.Desogestrel: A synthetic progestational hormone used often as the progestogenic component of combined oral contraceptive agents.Norpregnenes: Pregnenes with one double bond or more than three double bonds which have undergone ring contractions or are lacking carbon-18 or carbon-19..Hydroxyprogesterones: Metabolites or derivatives of PROGESTERONE with hydroxyl group substitution at various sites.Contraceptives, Oral, Synthetic: Oral contraceptives which owe their effectiveness to synthetic preparations.Contraceptives, Oral, Combined: Fixed drug combinations administered orally for contraceptive purposes.Mifepristone: A progestational and glucocorticoid hormone antagonist. Its inhibition of progesterone induces bleeding during the luteal phase and in early pregnancy by releasing endogenous prostaglandins from the endometrium or decidua. As a glucocorticoid receptor antagonist, the drug has been used to treat hypercortisolism in patients with nonpituitary CUSHING SYNDROME.Estradiol: The 17-beta-isomer of estradiol, an aromatized C18 steroid with hydroxyl group at 3-beta- and 17-beta-position. Estradiol-17-beta is the most potent form of mammalian estrogenic steroids.20-alpha-Dihydroprogesterone: A biologically active 20-alpha-reduced metabolite of PROGESTERONE. It is converted from progesterone to 20-alpha-hydroxypregn-4-en-3-one by the 20-ALPHA-HYDROXYSTEROID DEHYDROGENASE in the CORPUS LUTEUM and the PLACENTA.Norethynodrel: A synthetic progestational hormone with actions and uses similar to those of PROGESTERONE. It has been used in the treatment of functional uterine bleeding and endometriosis. As a contraceptive, it has usually been administered in combination with MESTRANOL.Hormone Replacement Therapy: Therapeutic use of hormones to alleviate the effects of hormone deficiency.5-alpha-Dihydroprogesterone: A biologically active 5-alpha-reduced metabolite of plasma PROGESTERONE. It is the immediate precursor of 5-alpha-pregnan-3-alpha-ol-20-one (ALLOPREGNANOLONE), a neuroactive steroid that binds with GABA(A) RECEPTOR.Contraceptive Agents, Female: Chemical substances or agents with contraceptive activity in females. Use for female contraceptive agents in general or for which there is no specific heading.Endometrial Hyperplasia: Benign proliferation of the ENDOMETRIUM in the UTERUS. Endometrial hyperplasia is classified by its cytology and glandular tissue. There are simple, complex (adenomatous without atypia), and atypical hyperplasia representing also the ascending risk of becoming malignant.Megestrol: 17-Hydroxy-6-methylpregna-3,6-diene-3,20-dione. A progestational hormone used most commonly as the acetate ester. As the acetate, it is more potent than progesterone both as a progestagen and as an ovulation inhibitor. It has also been used in the palliative treatment of breast cancer.Contraceptives, Oral, Hormonal: Oral contraceptives which owe their effectiveness to hormonal preparations.Intrauterine Devices, Medicated: Intrauterine devices that release contraceptive agents.Contraceptives, Oral: Compounds, usually hormonal, taken orally in order to block ovulation and prevent the occurrence of pregnancy. The hormones are generally estrogen or progesterone or both.Ethinyl Estradiol: A semisynthetic alkylated ESTRADIOL with a 17-alpha-ethinyl substitution. It has high estrogenic potency when administered orally, and is often used as the estrogenic component in ORAL CONTRACEPTIVES.Lynestrenol: A synthetic progestational hormone used often in mixtures with estrogens as an oral contraceptive.Postmenopause: The physiological period following the MENOPAUSE, the permanent cessation of the menstrual life.Endometrium: The mucous membrane lining of the uterine cavity that is hormonally responsive during the MENSTRUAL CYCLE and PREGNANCY. The endometrium undergoes cyclic changes that characterize MENSTRUATION. After successful FERTILIZATION, it serves to sustain the developing embryo.Dydrogesterone: A synthetic progestational hormone with no androgenic or estrogenic properties. Unlike many other progestational compounds, dydrogesterone produces no increase in temperature and does not inhibit OVULATION.Androstenes: Unsaturated derivatives of the steroid androstane containing at least one double bond at any site in any of the rings.Chlormadinone Acetate: An orally active synthetic progestational hormone used often in combinations as an oral contraceptive.Cyproterone Acetate: An agent with anti-androgen and progestational properties. It shows competitive binding with dihydrotestosterone at androgen receptor sites.Drug Implants: Small containers or pellets of a solid drug implanted in the body to achieve sustained release of the drug.Melengestrol Acetate: A 6-methyl PROGESTERONE acetate with reported glucocorticoid activity and effect on ESTRUS.Megestrol Acetate: Megestrol acetate is a progestogen with actions and uses similar to those of the progestogens in general. It also has anti-androgenic properties. It is given by mouth in the palliative treatment or as an adjunct to other therapy in endometrial carcinoma and in breast cancer. Megestrol acetate has been approved to treat anorexia and cachexia. (From Reynolds JEF(Ed): Martindale: The Extra Pharmacopoeia (electronic version). Micromedex, Inc, Englewood, CO, 1995)20-Hydroxysteroid Dehydrogenases: A group of enzymes that catalyze the reversible reduction-oxidation reaction of 20-hydroxysteroids, such as from a 20-ketosteroid to a 20-alpha-hydroxysteroid (EC or to a 20-beta-hydroxysteroid (EC Neoplasms: Tumors or cancer of ENDOMETRIUM, the mucous lining of the UTERUS. These neoplasms can be benign or malignant. Their classification and grading are based on the various cell types and the percent of undifferentiated cells.Menopause: The last menstrual period. Permanent cessation of menses (MENSTRUATION) is usually defined after 6 to 12 months of AMENORRHEA in a woman over 45 years of age. In the United States, menopause generally occurs in women between 48 and 55 years of age.Climacteric: Physiologic period, characterized by endocrine, somatic, and psychic changes with the termination of ovarian function in the female. It may also accompany the normal diminution of sexual activity in the male.Nandrolone: C18 steroid with androgenic and anabolic properties. It is generally prepared from alkyl ethers of ESTRADIOL to resemble TESTOSTERONE but less one carbon at the 19 position.Uterine Hemorrhage: Bleeding from blood vessels in the UTERUS, sometimes manifested as vaginal bleeding.Estrus Synchronization: Occurrence or induction of ESTRUS in all of the females in a group at the same time, applies only to non-primate mammals with ESTROUS CYCLE.Breast Neoplasms: Tumors or cancer of the human BREAST.Flurogestone Acetate: A synthetic fluorinated steroid that is used as a progestational hormone.17-alpha-Hydroxyprogesterone: A metabolite of PROGESTERONE with a hydroxyl group at the 17-alpha position. It serves as an intermediate in the biosynthesis of HYDROCORTISONE and GONADAL STEROID HORMONES.Contraceptive Agents, Male: Chemical substances or agents with contraceptive activity in males. Use for male contraceptive agents in general or for which there is no specific heading.Pregnanediones: Pregnane derivatives in which two side-chain methyl groups or two methylene groups in the ring skeleton (or a combination thereof) have been oxidized to keto groups.Algestone: A synthetic progestational dihydroxy derivative of PROGESTERONE. Its acetonide possesses anti-inflammatory properties.Receptors, Estrogen: Cytoplasmic proteins that bind estrogens and migrate to the nucleus where they regulate DNA transcription. Evaluation of the state of estrogen receptors in breast cancer patients has become clinically important.Mestranol: The 3-methyl ether of ETHINYL ESTRADIOL. It must be demethylated to be biologically active. It is used as the estrogen component of many combination ORAL CONTRACEPTIVES.Hormone Antagonists: Chemical substances which inhibit the function of the endocrine glands, the biosynthesis of their secreted hormones, or the action of hormones upon their specific sites.Pregnanolone: A pregnane found in the urine of pregnant women and sows. It has anesthetic, hypnotic, and sedative properties.Estradiol Dehydrogenases: Enzymes that catalyze the oxidation of estradiol at the 17-hydroxyl group in the presence of NAD+ or NADP+ to yield estrone and NADH or NADPH. The 17-hydroxyl group can be in the alpha- or beta-configuration. EC Excision of the uterus.Estrus: The period in the ESTROUS CYCLE associated with maximum sexual receptivity and fertility in non-primate female mammals.Pregnenolone: A 21-carbon steroid, derived from CHOLESTEROL and found in steroid hormone-producing tissues. Pregnenolone is the precursor to GONADAL STEROID HORMONES and the adrenal CORTICOSTEROIDS.Contraceptive Agents: Chemical substances that prevent or reduce the probability of CONCEPTION.Uterine Neoplasms: Tumors or cancer of the UTERUS.Steroids: A group of polycyclic compounds closely related biochemically to TERPENES. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (STEROLS), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. (From Hawley's Condensed Chemical Dictionary, 11th ed)Uterus: The hollow thick-walled muscular organ in the female PELVIS. It consists of the fundus (the body) which is the site of EMBRYO IMPLANTATION and FETAL DEVELOPMENT. Beyond the isthmus at the perineal end of fundus, is CERVIX UTERI (the neck) opening into VAGINA. Beyond the isthmi at the upper abdominal end of fundus, are the FALLOPIAN TUBES.Pregnanediol: An inactive metabolite of PROGESTERONE by reduction at C5, C3, and C20 position. Pregnanediol has two hydroxyl groups, at 3-alpha and 20-alpha. It is detectable in URINE after OVULATION and is found in great quantities in the pregnancy urine.Ovariectomy: The surgical removal of one or both ovaries.20-alpha-Hydroxysteroid Dehydrogenase: An enzymes that catalyzes the reversible reduction-oxidation reaction of 20-alpha-hydroxysteroids, such as from PROGESTERONE to 20-ALPHA-DIHYDROPROGESTERONE.Pregnanes: Saturated derivatives of the steroid pregnane. The 5-beta series includes PROGESTERONE and related hormones; the 5-alpha series includes forms generally excreted in the urine.Ovulation: The discharge of an OVUM from a rupturing follicle in the OVARY.Estradiol Antagonists: Compounds which inhibit or antagonize the biosynthesis or action of estradiol.Trenbolone Acetate: An anabolic steroid used mainly as an anabolic agent in veterinary practice.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Estradiol Congeners: Steroidal compounds related to ESTRADIOL, the major mammalian female sex hormone. Estradiol congeners include important estradiol precursors in the biosynthetic pathways, metabolites, derivatives, and synthetic steroids with estrogenic activities.Corpus Luteum: The yellow body derived from the ruptured OVARIAN FOLLICLE after OVULATION. The process of corpus luteum formation, LUTEINIZATION, is regulated by LUTEINIZING HORMONE.Ovary: The reproductive organ (GONADS) in female animals. In vertebrates, the ovary contains two functional parts: the OVARIAN FOLLICLE for the production of female germ cells (OOGENESIS); and the endocrine cells (GRANULOSA CELLS; THECA CELLS; and LUTEAL CELLS) for the production of ESTROGENS and PROGESTERONE.Danazol: A synthetic steroid with antigonadotropic and anti-estrogenic activities that acts as an anterior pituitary suppressant by inhibiting the pituitary output of gonadotropins. It possesses some androgenic properties. Danazol has been used in the treatment of endometriosis and some benign breast disorders.Menstruation: The periodic shedding of the ENDOMETRIUM and associated menstrual bleeding in the MENSTRUAL CYCLE of humans and primates. Menstruation is due to the decline in circulating PROGESTERONE, and occurs at the late LUTEAL PHASE when LUTEOLYSIS of the CORPUS LUTEUM takes place.Spermatogenesis-Blocking Agents: Chemical substances which inhibit the process of spermatozoa formation at either the first stage, in which spermatogonia develop into spermatocytes and then into spermatids, or the second stage, in which spermatids transform into spermatozoa.Dihydrotestosterone: A potent androgenic metabolite of TESTOSTERONE. It is produced by the action of the enzyme 3-OXO-5-ALPHA-STEROID 4-DEHYDROGENASE.Dimethisterone: A synthetic progestational hormone without significant estrogenic or androgenic properties. It was formerly used as the progestational component in oral sequential contraceptives.Androgens: Compounds that interact with ANDROGEN RECEPTORS in target tissues to bring about the effects similar to those of TESTOSTERONE. Depending on the target tissues, androgenic effects can be on SEX DIFFERENTIATION; male reproductive organs, SPERMATOGENESIS; secondary male SEX CHARACTERISTICS; LIBIDO; development of muscle mass, strength, and power.Contraceptives, Oral, Sequential: Drugs administered orally and sequentially for contraceptive purposes.Menstruation-Inducing Agents: Chemical compounds that induce menstruation either through direct action on the reproductive organs or through indirect action by relieving another condition of which amenorrhea is a secondary result. (From Dorland, 27th ed)Metrorrhagia: Abnormal uterine bleeding that is not related to MENSTRUATION, usually in females without regular MENSTRUAL CYCLE. The irregular and unpredictable bleeding usually comes from a dysfunctional ENDOMETRIUM.Drug Combinations: Single preparations containing two or more active agents, for the purpose of their concurrent administration as a fixed dose mixture.Gonanes: Steroids containing the fundamental tetracyclic unit with no methyl groups at C-10 and C-13 and with no side chain at C-17. The concept includes both saturated and unsaturated derivatives.3-Hydroxysteroid Dehydrogenases: Catalyze the oxidation of 3-hydroxysteroids to 3-ketosteroids.Pregnancy Maintenance: Physiological mechanisms that sustain the state of PREGNANCY.