Lecture 32 Flashcards
What are the common features of oral contraceptives?
Contain analogues of the sex steroids progesterone and estrogen
Provide effective, tolerable and reversible preventing of pregnancy
Theoretical failure rate of <2% Actual failure rate between 3-5% due to lack of compliance
Used by more than 100 million women worldwide
What are the aims of oral contraceptives?
Aim is to prevent pregnancy
Switch of pituitary gland hormones driving ovulation
Make the uterus non-receptive to implantation of fertilised egg
What are the fertility regulating hormones?
Gonadotrophin releasing hormone Follicle stimulating hormone Luteinizing hormone Progesterone Estrogen
What is the role of the Hypothalamin-Pituitary-gonadal axis in a womens fertility cycle?
The hypothalamus releases Gonadotropin releasing hormone which causes follicle stimulating hormone and luteinizing hormone to be released by the pituitary gland resulting in estrogen and progesterone being released by the ovaries
What is the cycle of fertility hormones?
Follicle stimulating hormone increases gradually as does the Estradiol until a sudden, rapid peak of luteinizing hormone is released along with a peak of follicle stimulating hormone during ovulation
THere is then a large increase in progesterone while estradiol has a slightly lower peak and the other hormones decrease to a very low level
What is the relationship between oral contraceptives and the hypothalamic-pituitary-gonadal axis?
Oral contraceptives alter this axis by extending the biological half lives of some hormones through the use of synthetic hormones so the pill can be taken only once per day
As the pill is taken by those who are not ill, the lowest possible dose is used to try and prevent adverse effects
What are the two types of oral contraceptives?
Combined Oral Contraceptives which contain estrogen and a progestin and are the most common
Progestin only contraceptives which are less common
What are the common components of combined oral contraceptives?
Contain both a progestin and estrogen
The estrogen is usually ethinyl estradiol while the progestin varies from 2nd generation norethisterone etc and 3rd generation desogestrel etc
The menstruation period is carried out by dummy pills that are taken near the end of the cycle
Compliance is key with a 12 hour window for a missed pill
What are the different types of combined oral contraceptives?
Monophasic where each tablet contains a constant dose of estrogen and progestin through out the monthly cycle
Biphasic where the estrogen is constant but the progestin is increased in the second half of the monthly cycle
Triphasic where the dose of estrogen is higher in the middle of the cycle or remains constant and progestin increases in three steps during the monthly cycle
What are progestin only contraceptives?
The mini pill sometimes used as high doses of estrogen have been associatedwith cardiovascular events
Suitable for women who cannot take estrogen due to breastfeeding or previous cardiovascular conditions
Slightly less effective than combination pills taken every 24 hours without a break and only a 3 hour compliance window
What is the mechanism of action of progestin only contraceptives?
They prevent ovulation and thicken the cervical mucus to prevent entry of sperm to uterus
reduce the motility of the fallopian tubes to inhibit passage of the sperm towards the egg
Thin endometrium to prevent implantation of the embryo
What is the mechanism of action of estrogen?
Prevents release of FSH by acting as a negative feedback on the anterior pituitary suppressing the development of ovarian follicle
Inhibits development of uterine lining to discourage implantation
Alters co-ordination of contractions of cervix, uterus and fallopian tubes to hinder fertilization and implantation
What is the mechanism of action of progestin?
Inhibits secretion of LH and FSH through negative feedback and suppresses ovulation
Increases the thickness of cervical mucus to decrease sperm motility
Inhibits development of uterine lining to discourage implantation
Alters co-ordination of contractions of cervix, uterus and fallopian tubes to hinder fertilization and implantation
What are the common side effects of combined oral contraceptives?
Headache, mood changes, depression Fluid retention, weight changes Nausea, vomiting Menstrual cramps, breakthrough bleeding These side effects can usually be avoided by changing to a different type of combined oral contraceptive
What are the serious side effects of combined oral contraceptives?
Possible small increased risk of breast cancer
Hypertension
Increased risk of cardiovascular disease such as deep vein thrombosis, pulmonary embolism, stroke and myocardial infarction
These risks are very, very low however and in fact some of them like deep vein thrombosis there is a smaller increase in risk when taking the pill than there would be if the women became pregnant
