Block 9 - L2-L4 Flashcards
What are the physiological effects of estrogen on female reproduction?
Regulation of menstrual cycle and ovulation
What are the physiological effects of estrogen on female puberty?
Development and maturation of secondary sexual characteristics
What are the physiological effects of estrogen on electrolyte and fluid balance?
Increases Na and H2O retention
What are the physiological effects of estrogen on the CNS?
Increases sense of well-being and enhances cognition
What are the physiological effects of estrogen on blood vessels?
Increases vasodilation
What are the physiological effects of estrogen on blood coagulation?
Increases coagulation and clotting factors
What are the physiological effects of estrogen on blood lipids?
Increases HDL and lowers LDL
What are the physiological effects of estrogen on bone?
Decreases bone resorption, maintains BMD, helps close epiphysis
What is the MOA of estrogen?
- Estrogen binds ER in the cytosol (unbinds from SHBG and diffuses into the cell prior to this)
- ER undergoes conformational changes and forms dimers
- ER dimers translocate into the nucleus and bind to target promoters (ERE - estrogen response element)
- Promoter-bound, ligand-activated ER receptors recruit transcriptional co-factors and modulate target gene expression
List the natural endogenous estrogens in order of potency.
Most potent: estradiol (E2)
Middle potency: estrone (E1)
Least potent: estriol (E3)
When are the three natural endogenous estrogens most abundant?
E2 - reproductive years
E1 - menopause
E3 - pregnancy
Where is E2 produced?
Ovary (most), adipose tissue, adrenal glands, liver, breast, neurons
Where is E1 produced?
Ovary, adipose tisue
Where is E3 produced?
Secreted from placenta and adrenal gland (not ovary), also a metabolite of E2 and E3 in the liver
What is the role of aromatase (CYP19A1) in the production of estrogens?
Aromatase converts Androstendione to Estrone (E1) and Testosterone to Estradiol (E2). These are converted to Estriol (E3) in the liver and placenta.
What converts E1 to E2 and E2 to E1?
17-beta-HSD
How is estrogen biosynthesis regulated?
Negative feedback via Estrogen and Inhibin
Discuss different administrations of E2.
- Significant first pass effect after oral administration (low oral bioavailability)
- Metabolized in liver to E1 and E3
- Major effect on liver (clotting factors, lipids, etc.)
- Transdermal preparations avoid first pass effect (lower risk of thrombosis and stroke)
How is oral bioavailability of synthetic estrogens improved?
Modifications - conjugated estrogens, estrogen esters, esterified estrogens
Discuss CYP metabolism of estrogens.
Extensively metabolized by CYP 1A2, 2C9, 3A4
inducers of CYP3A4 - St. John’s Wort, carbamazepine, phenobarbital decrease estrogen levels
How are Phase II estrogen conjugates excreted?
Urine and bile (undergo enterohepatic recirculation, explaining extensive hepatic actions)
List the 4 estrogen preparations and formulations for clinical use.
- Ethinylestradiol (EE)
- Conjugated equine estrogens (CEE - Premarin)
- Esterified estrogens (EE)
- Estrogen esters
What are the clinical uses of estrogen?
- Hormone replaceent therapy for post-menopausal women (+/- progestin)
- Component of oral contraceptive pill
- Treatment of primary hypogonadism
- Primary ovarian insufficiency
Discuss risk of endometrial cancer in estrogen hormone replacement therapy.
When the uterus present, estrogen along has a 6.3x increased risk of developing endometrial cancer. This risk is removed in the presence of a progestin.
Discuss treatment of primary hypogonadism (Turner’s syndrome, etc.) with estrogen.
Used at ~11-13 years to promote development of secondary sexual characteristics, promote optimal growth and prevent osteoporosis; progestin needed to prevent endometrial hyperplasia, gonadotropin treatment required to rescue fertility
What is menopause?
Natural process of aging involving permanent cessation of the menstrual cycle (12 months after last period) due to oocyte depletion (sharp decrease in ovarian production of estrogen and progesterone)
What is the mean age of onset of menopause and the age range?
51 y/o (45-60 y/o)
What are other causes of menopause?
Gynecological surgery (hysterectomy, endometrial ablation), premature ovarian failure (idiopathic, autoimmune, PCOS)
When do symptoms of menopause occur?
~4 years prior to the final menstrual cycle
What are the signs and symptoms of menopause?
Irregular menstrual cycles Vasomotor responses (hot flashes) - most common Sleep disturbances Mood swings/depression Vaginal dryness and atrophy Sexual dysfunction Cognitive decline (memory loss/ability to concentrate) Joint pain
What are long term consequences of estrogen deficiency?
Increased bone loss
Increased risk fo CVD
Skin changes
What is the goal of hormone replacement therapy for treatment of menopausal symptoms?
Provide relief of symptoms, especially vasomotor symptoms, vaginal dryness and atrophy, mood lability/depression, and joint pains
Treatment to prevent chronic effects of estrogen deficiency is no longer recommended due to increased risk of AE
What are the benefits to various routes of estrogen therapy?
Transdermal E2 - lower risk of VTE, stroke, hypertriglyceridemia
Oral - more favorable lipid effect (increases HDL)
Vaginal - if primary treatment is for GU symptoms
Why is progestin added to various treatments with estrogen?
Prevent endometrial hyperplasia when a uterus is present
Discuss the duration of estrogen therapy.
No more than 5 years or beyond the age of 60 y/o
What are the contraindications of estrogen?
Prior history of or high risk for (BRCA1+, etc.) breast cancer, CHD, stroke, history of endometrial cancer, liver disease, history of thromboembolic disease, history of genital bleeding, heavy smoking (increased stroke risk)
What are the AE of estrogen?
- Increased risk of endometrial cancer
- Increased risk of thromboembolic disease
- Increased risk of gallbladder disease (increased hepatic secretion of cholesterol)
- Post-menopausal uterine bleeding
- Fullness/tenderness of breast
- Severe migraines
- Increased risk of dementia (if taking estrogen >65 y/o)
What do estrogen do in breast cancer?
If ER+, increases growth of the tumor
What are SERMs (selective estrogen receptor modulators)?
ER ligands that exhibit mixed agonist/antagonist activity in a tissue-specific fashion; act as ER antagonists in some tissues and partial agonists in others
List the SERMs.
- Tamoxifen
- Raloxifene
- Clomiphene
What are the sites of action for Tamoxifen?
Antagonist - breast tissue
Partial agonist - endometrium, bone
What are the sites of action for Raloxifene?
Antagonist - breast tissue, endometrium
Partial agonist - bone
What are the sites of action for Clomiphene?
Antagonist - hypothalamus, AP, uterus, vagina
Partial agonist - ovaries
What is the MOA of SERMs?
Bind directly to the ligand binding site of the ER and compete for binding with endogenous E2; induce a different conformation in the ER compared to E2; different conformations bind to distinct subsets of tissue-specific transcriptional co-factors and thereby activate distinct patterns of gene expression
What are the indications of Tamoxifen?
- Primary prevention in women at high risk of breast cancer
- Adjuvant therapy of women ER+ early, locally-advanced, and metastatic breast cancer
- Treatment of male gynecomastia
True or false - Tamoxifen resistance can occur.
True (both intrinsic and acquired)
What are the AE of Tamoxifen?
- Hot flashes (ER antagonism in CNS)
- Increased risk of thromboembolic events
- Increased risk of endometrial cancer (agonist effect)
What are the indications of Raloxifene?
- Treatment of osteoporosis in post-menopausal women due to E2 deficiency (activates ER in bone)
- Primary prevention of breast cancer in high risk patients
Why would Raloxifene be used instead of Tamoxifen in prevention of breast cancer?
Raloxifene is not associated with increased risk of endometrial cancer, but it is about 75% as effective
What are the AE of Raloxifene?
Hot flahses, increased risk of thromboembolic events (less than tamoxifen), leg cramps
What is the indication of Clomiphene?
Female infertility due to anovulation (PCOS, etc.)
What is the MOA of Clomiphene?
Antagonizes ER in the hypothalamus and AP, prevents negative feedback, promotes increased expression of GnRH, gonadotropins, FSH, LH, increases follicular development; improves ovulatory and pregnancy rate
What are the AE of Clomiphene?
Hot flashes Multiple pregnancy (only rarely leads to ovarian hyperstimulation syndrome)
What is the selective estrogen receptor degrader (SERD)?
Fulvestrant
What is the MOA of Fulvestrant?
Binds to ER, inducing an abnormal conformation that results in the subsequent degradation of the ER protein; acts as a pure anti-estrogen (no agonist activity)
What are the indications of Fulvestrant?
Treatment of ER+ advanced/metastatic breast cancer in post-menopausal women with disease progression following prior anti-estrogen therapy (tamoxifen, etc.)