Sex steroids Flashcards
What is the mechanism of action of sex steroids ?
Both oestrogens and progesterones act by influencing gene transcription. The receptors are in the cytoplasm or in the cell nucleus bound to heat shock proteins.
Heat shock proteins dissociate when hormone bunds and receptor hormone complex is transported into nucleus to produce transcription
How does the combined oral contraceptive pill provide contraception?
Suppression of FSH release to prevent development of follicles in ovary.
This means that production of oestradiol is impaired
This impairs mid cycle LH surge which is needed for ovulation to occur.
How does the progesterone only pill provide contraception?
Produces asynchronous development of endometrium with stromal thinning so it makes it harder for a fertilised ovum to implant. It also slows fallopian tube motility and makes cervical mucus thicker and more acidic.
When is use of the COCP contraindicated?
Thromboembolitic disorders
Hypertension
Ischaemic heart disease
Breast cancer, cervical cancer
What are the side effects of COCPs and POPs?
Thromboembolism
Ischaemic heart disease
Increase in BP
Increased risk of breast cancer and cervical cancer
Increase in HDL, decrease in LDL and increase in TGs
Cholestatic jaundice
What are the adverse drug reactions of COCPs and POPs?
Antibacterials (enzyme inducers)- rifampicin and rifabutin
Antidepressants- st johns wort
Anticonvulsants (enzyme inducing) eg carbamazepine
Antiretrovirals
Why are sex steroid hormones given for menopause?
Oestrogens are given at a much lower dose to reduce symptoms of post menopausal hormone deficiency.
What can happen if HRT is given to a woman with a uterus for a few weeks without progesterone also?
In what situations can oestrogen be given alone?
Cystic hyperplasia can occur
Oestrogen can be given alone if the woman has had a hysterectomy.
What are the major side effects of HRT?
Increased risk of breast cancer Increased risk of stroke Breast pain, abdominal leg cramps Nausea and vomiting Headache, dizziness Increased risk of venous thromboembolism
What is the mechanism of action of clomiphene?
Inhibits oestrogen binding to its receptor in the anterior pituitary so inhibits negative feedback, results in increased FSH and LH expression= so can promote ovulation.
What is the mechanism of action of tamoxifen?
Binds to oestrogen receptor in breast tissue and blocks oestrogen stimulated myoepithelial cell division. Also causes ovulation induction.
What is the mechanism of action of the anti progestin- mifepristone?
Partial agonist to progesterone receptor, so inhibitsprogesterone action. Sensitises uterus to prostaglandins so used for medical termination of pregnancy and induction of labour.
What is the mechanism of action and use of the anti androgen cyproterone?
Weak progestogenic effect. Partial agonist at progesterone receptor. Used to treat advanced prostate cancer.
What is the mechanism of action of the SERM raloxifene?
Protects against osteoporosis. Reduces risk of invasive breast cancer, has oestrogenic effects of bone, lipid metabolism and blood coagulation.
No proliferative effects on endometrium and breast.
