Endocrinology 2nd December 2016 Control of Fertility: Hormonal contraception Role of gonadotrophins: · Maturation of follicles · Control of ovulation · Formation of corpus luteum Endocrine role of the ovary · Oestrogens, progesterone, inhibin Contraception Block sperm transport to ovum · Natural methods, coitus interrupts · Barrier methods · Chemical spermicides (NOT alone!) Prevention of ovulation - prevent that one egg from being released and that is effective contraception · Oral contraceptives - great route as it is convenient and you just put one dose in; if you have a reaction you can stop taking, with injections you don't have the ability to do that, the dose lasts a long period of time. o Combined o Progesterone only · Implants - cannot reverse · IUDs · Depot injections · Blockage of implantation - there will be no baby, as there could be the egg and sperm meet, but the fertilised egg may not implant into the uterine wall - abortion is deciding to remove the baby, if there is inhibiting of implantation that is contraception o IUD (Intrauterine device - can also contain hormones) · Emergency contraception o "Morning after pill" prevents implantation and it is not effective after implantation · (NOT an abortifacient) The HPG When give the hormones from the outside, we are imitating the negative feedback mechanisms - we are trying to prevent the HPG cycle Have progesterone in the system and it will stop you from ovulating, as it is involved in maintenance of pregnancy.
2nd December 2016 Endocrinology Effects of EXOGENOUS gonadal steroids Development of oral contraceptives 1920s: Observation that ovarian extracts could be used in the control of fertility. Physiological mechanism known: · Pregnant women do not ovulate · Persistence of corpus luteum causes infertility Progesterone interferes with ovulation (animal studies) 1930s: Potent oral oestrogen synthesised, ethinyloestradiol (synthetic progesterone and mimic its actions). Progesterone synthesised from a steroid found in Mexican yams. 1951: synthesis of norethisterone, an orally active progesterone analogue (that's the one we want). If you take progesterone consistently, the woman won't bleed - falling levels of progesterone is natural and allows for the shedding of the uterine wall. Trials of progesterone Stopping progesterone treatment causes a withdrawal bleed - to change the lining of the uterine wall · NOT a "real" period! 21 days with 7 day break so we produce a break for the menstrual bleed: good response & regular bleeding. But when a purified progesterone used there is an increase in pregnancy rate & menstrual disturbance; it wasn't just progesterone in the first drug! "Impurity" in the previous dirty progesterone was identified as an oestrogen Combined oral contraceptives (COCs) > Causes of side effects Must remember to take it, otherwise you can get pregnant First COC in USA late 1950s, in UK in 1961 · Efficacy quickly established Association with cardiovascular disease quickly became apparent: (venous thrombo-embolism). Associated with the oestrogen component and rapidly reduced the concentration of it in the COC OESTROGEN component of COC responsible · Original