1. Steroids: Estrogen and Progestin Jennifer Kettel Professor John Buynak CHEM 5398 March 27, 2007 Jennifer Kettel Professor John Buynak CHEM 5398 March 27, 2007

2. Introduction Estrogens Progestins Hormone Contraceptives –Combination Contraceptives –Progestin-Only Contraceptives –Emergency Contraceptives Estrogens Progestins Hormone Contraceptives –Combination Contraceptives –Progestin-Only Contraceptives –Emergency Contraceptives

3. Estrogens and Progestins Estrogens and progestins are hormones that produce many physiological actions In women, –Developmental effects (estrogens are largely responsible for pubertal changes in girls and secondary sexual characteristics) –Neuroendocrine actions involved in: Control of ovulation and the preparation of the reproductive tract for fertilization and implantation –Major Actions on: Minerals, Carbohydrates, Proteins, and Lipid Metabolism In men, effects: –Bone –Spermatogenesis –Behavior Estrogens and progestins are hormones that produce many physiological actions In women, –Developmental effects (estrogens are largely responsible for pubertal changes in girls and secondary sexual characteristics) –Neuroendocrine actions involved in: Control of ovulation and the preparation of the reproductive tract for fertilization and implantation –Major Actions on: Minerals, Carbohydrates, Proteins, and Lipid Metabolism In men, effects: –Bone –Spermatogenesis –Behavior

4. Estrogens A group of steroid hormones that readily diffuse across the cell membrane Inside the cell, they interact with estrogen receptors A group of steroid hormones that readily diffuse across the cell membrane Inside the cell, they interact with estrogen receptors EstriolEstradiolEstrone A A A DDD

5. Estrogen Synthesis Estrogen is produced primarily by developing follicles in the ovaries, the corpus luteum, and the placenta Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) stimulate the production of estrogen in the ovaries Some estrogens are also produced in smaller amounts by other tissues such as the liver, adrenal glands, and the breasts The ovaries are the principal source of circulating estrogen in premenopausal women, with estrodiol being the main secretory product In postmenopausal women, the principal circulating estrogen estrone, which is synthesized from dehydroepiandrosterone and secreted by the adrenals Estrogen is produced primarily by developing follicles in the ovaries, the corpus luteum, and the placenta Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) stimulate the production of estrogen in the ovaries Some estrogens are also produced in smaller amounts by other tissues such as the liver, adrenal glands, and the breasts The ovaries are the principal source of circulating estrogen in premenopausal women, with estrodiol being the main secretory product In postmenopausal women, the principal circulating estrogen estrone, which is synthesized from dehydroepiandrosterone and secreted by the adrenals

6. Estrogen Synthesis The most potent naturally occurring estrogen in humans for both the Estrogen Receptor alpha- and beta-mediated actions is 17beta-estradiol, followed by estrone and estriol Each estrogen contains a phenolic A ring with a hydroxyl group at carbon 3 and a beta-OH or ketone in position 17 of ring D The phenolic A ring is the principal structural feature responsible for selective, high-affinity binding to both receptors Synthesis of estrogen begins from the synthesis of androstenedione from cholesterol Androstenedione crosses the basal membrane into surrounding granulosa cells, where its converted to estrone or estradiol wither immediately or through testosterone The conversion is catalyzed by aromatase The most potent naturally occurring estrogen in humans for both the Estrogen Receptor alpha- and beta-mediated actions is 17beta-estradiol, followed by estrone and estriol Each estrogen contains a phenolic A ring with a hydroxyl group at carbon 3 and a beta-OH or ketone in position 17 of ring D The phenolic A ring is the principal structural feature responsible for selective, high-affinity binding to both receptors Synthesis of estrogen begins from the synthesis of androstenedione from cholesterol Androstenedione crosses the basal membrane into surrounding granulosa cells, where its converted to estrone or estradiol wither immediately or through testosterone The conversion is catalyzed by aromatase

7. Biosynthetic Pathway This figure shows the major metabolic intermediates in the usual synthesis of estrogen, starting with cholesterol, proceeding to pregnenolone, an androgen, and then estrogen. http://www.chemistryexplained.com/Di-Fa/Estrogen.html

8. Estrogen Receptors Estrogens exert their effects by interaction with receptors that are members of the super family of nuclear receptors The two estrogen receptor (ER) genes are located on separate chromosomes: ESR1 encodes ER-alpha and ESR2 encodes ER- beta Both ERs are estrogen-dependent nuclear transcription factors that have different tissue distributions and transcriptional regulatory effects on target genes Both ERs are ligand-activated transcription factors that increase or decrease the transcription of target genes After entering the cell by passive diffusion through the plasma membrane, the hormone binds to an ER in the nucleus In the nucleus, the ER is present as an inactive monomer bound to heat-shock proteins, and upon binding estrogen, a change in ER confirmation dissociates the heat-shock proteins and causes receptor dimerization, which increases the affinity and the rate of receptor binding to DNA Estrogens exert their effects by interaction with receptors that are members of the super family of nuclear receptors The two estrogen receptor (ER) genes are located on separate chromosomes: ESR1 encodes ER-alpha and ESR2 encodes ER- beta Both ERs are estrogen-dependent nuclear transcription factors that have different tissue distributions and transcriptional regulatory effects on target genes Both ERs are ligand-activated transcription factors that increase or decrease the transcription of target genes After entering the cell by passive diffusion through the plasma membrane, the hormone binds to an ER in the nucleus In the nucleus, the ER is present as an inactive monomer bound to heat-shock proteins, and upon binding estrogen, a change in ER confirmation dissociates the heat-shock proteins and causes receptor dimerization, which increases the affinity and the rate of receptor binding to DNA

9. Anti-estrogens and SERMs Anti-estrogens –Pure antagonists –Clomiphene is for treatment of infertility in anovulatory women –Fulvestrant is used for the treatment of breast cancer Anti-estrogens –Pure antagonists –Clomiphene is for treatment of infertility in anovulatory women –Fulvestrant is used for the treatment of breast cancer Selective Estrogen Receptor Modulators (SERMs) –Compounds with tissue-selective actions –The goal of these drugs is to produce beneficial estrogenic actions in certain tissues (ex. Brain, bone, liver) during postmenopausal hormone therapy –Tamoxifen, Raloxifen, Toremifine Selective Estrogen Receptor Modulators (SERMs) –Compounds with tissue-selective actions –The goal of these drugs is to produce beneficial estrogenic actions in certain tissues (ex. Brain, bone, liver) during postmenopausal hormone therapy –Tamoxifen, Raloxifen, Toremifine

10. Progestins Progestins include the naturally occurring hormone progesterone, 17  -acetoxyprogesterone derivatives in the pregnane series, 19-nortestosterone derivatives (estranges), and norgestrel and related compounds in the gonane series progesterone 17  -acetoxyprogesterone 19-nortestosterone norgestrel levonorgestrel

11. Physcical Actions of Progesterone In the reproductive tract, progesterone decreases estrogen-driven endometrial proliferation and leads to the development of a secretory endometrium The abrupt decline in progesterone at the end of the cycle is the main determinant of the onset of menstruation Progesterone is very important for the maintenance of pregnancy It suppresses menstruation and uterine contractility In the reproductive tract, progesterone decreases estrogen-driven endometrial proliferation and leads to the development of a secretory endometrium The abrupt decline in progesterone at the end of the cycle is the main determinant of the onset of menstruation Progesterone is very important for the maintenance of pregnancy It suppresses menstruation and uterine contractility

12. The Progestin Receptor Unlike the ER receptor, which requires a phenolic ring for binding, the PR favors a non-phenolic ring structure There is a single gene that encodes two isoforms of the progesterone receptor (PR): PR-A and PR-B Since the ligand-binding domains of the two PR isoforms are identical, there is no difference in ligand binding However, the biological activities of PR-A and PR-B are distinct and depend on the target gene in question PR-B mediates the stimulatory activities of progesterone PR-A strongly inhibits this action of PR-B Upon binding progesterone, the heat-shock proteins dissociate, and the receptors are phosphorylated and subsequently form dimers (homo- and hetero-) that bind with high selectivity to progesterone response elements located on target genes Unlike the ER receptor, which requires a phenolic ring for binding, the PR favors a non-phenolic ring structure There is a single gene that encodes two isoforms of the progesterone receptor (PR): PR-A and PR-B Since the ligand-binding domains of the two PR isoforms are identical, there is no difference in ligand binding However, the biological activities of PR-A and PR-B are distinct and depend on the target gene in question PR-B mediates the stimulatory activities of progesterone PR-A strongly inhibits this action of PR-B Upon binding progesterone, the heat-shock proteins dissociate, and the receptors are phosphorylated and subsequently form dimers (homo- and hetero-) that bind with high selectivity to progesterone response elements located on target genes

13. Anti-progestins Anti-progestin, first discovered in 1981, is mifepristone, used to terminate pregnancy In the presence of progesterone, mifepristone acts as a competitive receptor antagonist for both progesterone receptors When administered in the early stages of pregnancy, mifepristone causes decidual breakdown by blocking uterine progesterone receptors, which leads to detachment of the blastocyst, decreasing hCG production Anti-progestin, first discovered in 1981, is mifepristone, used to terminate pregnancy In the presence of progesterone, mifepristone acts as a competitive receptor antagonist for both progesterone receptors When administered in the early stages of pregnancy, mifepristone causes decidual breakdown by blocking uterine progesterone receptors, which leads to detachment of the blastocyst, decreasing hCG production Mifepristone

14. Hormonal Contraceptives

15. Brief History At the beginning of the 20 th century, European scientists (Beard, Prenant, and Loeb) developed the concept that secretions of the corpus luteum suppressed ovulation during pregnancy By the 1930s, scientists had isolated and determined the structure of the steroid hormones and found that high doses of androgens, estrogens or progesterone inhibited ovulation At the beginning of the 20 th century, European scientists (Beard, Prenant, and Loeb) developed the concept that secretions of the corpus luteum suppressed ovulation during pregnancy By the 1930s, scientists had isolated and determined the structure of the steroid hormones and found that high doses of androgens, estrogens or progesterone inhibited ovulation

16. History cont. In June 1957, the FDA approved Enovid 10mg for menstrual disorders Later, in May 1960, the FDA approved Enovid for contraceptive use Although the FDA approved this drug for contraceptive use, it was not available to married women in all states until 1965 and unmarried women in all states until 1975 In June 1957, the FDA approved Enovid 10mg for menstrual disorders Later, in May 1960, the FDA approved Enovid for contraceptive use Although the FDA approved this drug for contraceptive use, it was not available to married women in all states until 1965 and unmarried women in all states until 1975

17. Types of Hormonal Contraceptives

18. Combination Contraceptives This type is the most frequently used in the United States, which contain both an estrogen and a progestin The theoretical efficacy is 99.9% Ethinyl estradiol (a synthetic estrogen) and mestranol are the estrogens most frequently used Levonorgestrel is the most common progestin used worldwide Currently, this type of contraceptives have lowered doses of estrogen (“low-dose”) This type is the most frequently used in the United States, which contain both an estrogen and a progestin The theoretical efficacy is 99.9% Ethinyl estradiol (a synthetic estrogen) and mestranol are the estrogens most frequently used Levonorgestrel is the most common progestin used worldwide Currently, this type of contraceptives have lowered doses of estrogen (“low-dose”)

19. Forms of Combination Contraceptives The Pill The Patch Vaginal Ring The Pill The Patch Vaginal Ring

20. Combination Contraceptives Mechanism of Action –Act by preventing ovulation –Measurements of plasma hormone levels indicate that LH and FSH levels are suppressed –The mid-cycle surge of LH is absent –Endogenous steroid levels are diminished –Thus, ovulation does not occur –The multiple actions of estrogens and progestins on the hypothalamic-pituitary-ovarian axis during the menstrual cycle and the efficacy of these agents all contribute to the blockade of ovulation Mechanism of Action –Act by preventing ovulation –Measurements of plasma hormone levels indicate that LH and FSH levels are suppressed –The mid-cycle surge of LH is absent –Endogenous steroid levels are diminished –Thus, ovulation does not occur –The multiple actions of estrogens and progestins on the hypothalamic-pituitary-ovarian axis during the menstrual cycle and the efficacy of these agents all contribute to the blockade of ovulation

21. Progestin-Only Contraceptives They contain progestins only, termed “mini pills” Slightly less effective, with 99% efficacy Forms –Pills –Injectables Their effectiveness is thought to be due largely to a thickening of cervical mucus, which decreases sperm penetration and impairs implantation They contain progestins only, termed “mini pills” Slightly less effective, with 99% efficacy Forms –Pills –Injectables Their effectiveness is thought to be due largely to a thickening of cervical mucus, which decreases sperm penetration and impairs implantation

22. Emergency Contraceptives The FDA has approved two preparations PLAN-B includes 2 doses of levonorgestrel separated by 12 hours (progestin-only) PREVEN is a 2 pill dose of a high-dose oral contraceptive (levonorgestrel and ethinyl estradiol) separated by 12 hours The first dose of these drugs should be taken 72 hours after intercourse The FDA has approved two preparations PLAN-B includes 2 doses of levonorgestrel separated by 12 hours (progestin-only) PREVEN is a 2 pill dose of a high-dose oral contraceptive (levonorgestrel and ethinyl estradiol) separated by 12 hours The first dose of these drugs should be taken 72 hours after intercourse PLAN B

23. Emergency Contraceptives Multiple mechanisms are likely to contribute to the efficacy of these agents, however, the exact mechanism is unknown These mechanisms include: –Ovulation is inhibited or delayed, alterations in endometrial receptivity for implantation –Interference with functions of the corpus luteum that maintain pregnancy –Production of a cervical mucus that decreases sperm penetration –Alterations in tubular transport of sperm, egg, or embryo –Effects on fertilization Emergency contraceptives do not interrupt pregnancy after implantation Multiple mechanisms are likely to contribute to the efficacy of these agents, however, the exact mechanism is unknown These mechanisms include: –Ovulation is inhibited or delayed, alterations in endometrial receptivity for implantation –Interference with functions of the corpus luteum that maintain pregnancy –Production of a cervical mucus that decreases sperm penetration –Alterations in tubular transport of sperm, egg, or embryo –Effects on fertilization Emergency contraceptives do not interrupt pregnancy after implantation

24. Side Effects Many side effects were found to be dose dependent, hence the development of the current low-dose preparations Side effects include: –Cardiovascular effects (hypertension, myocardial infarction, hemorrhagic stroke, venous thrombosis) –Breast, Hepatocellular, and Cervical Cancers –Endocrine and Metabolic effects Currently, its found that the low-dose preparations pose minimal health risks in women who have no predisposing risk factors Many side effects were found to be dose dependent, hence the development of the current low-dose preparations Side effects include: –Cardiovascular effects (hypertension, myocardial infarction, hemorrhagic stroke, venous thrombosis) –Breast, Hepatocellular, and Cervical Cancers –Endocrine and Metabolic effects Currently, its found that the low-dose preparations pose minimal health risks in women who have no predisposing risk factors

25. Male Birth Control? Current research and development is in various stages, some which include –A male version of “the pill” –A male hormonal contraceptive implanted under the skin –A drug which interferes with the maturation of sperm in the epididymis –Plugs that block the vas deferens Current research and development is in various stages, some which include –A male version of “the pill” –A male hormonal contraceptive implanted under the skin –A drug which interferes with the maturation of sperm in the epididymis –Plugs that block the vas deferens