Oral contraception ovulation inhibition

A low dosage of progestin ( mini-pill ) is used, in the form of medroxyprogesterone acetate, which is active at a very low dose. The mini-pill does not inhibit ovulation, but rather interferes with the endometrium and the cervical mucus. The use of this pill prevents most of the side effects of oral contraception, specifically nausea, water retention, and in some cases thrombophlebitis. However, a lower success rate and other frequent side effects have reduced the widespread acceptance of this preparation. Nevertheless, the mini-pill has a role to play in certain specific situations. For example, in an uncommon form of epilepsy called catamenial epilepsy, female patients will experience seizures at particular times during their menstrual cycle, reflecting the fact that seizure focus is stimulated by estrogens but inhibited by progestins. In such women, the mini-pill may afford not only birth control but also improved seizure control. 

Both of these compounds have potent estrogenic activity (inhibit ovulation) and are widely used as oral contraceptives. They are synthesized from the natural estrogen, estrone, by the following reaction ... 

Use of Hormones to Alter Normal Endocrine Function. Because of the intrinsic control mechanisms in the endocrine system, administration of exogenous hormones can often affect the normal release of hormones. This fact can be exploited in certain situations to cause a desired change in normal endocrine function. For instance, oral contraceptives containing estrogen and progesterone inhibit ovulation by inhibiting the release of LH and FSH from the anterior pituitary. 

The ovulation-inhibiting component of many oral contraceptive pills is a compound known as ethynyloestradiol, and this compound too is made by an alkynyllithium addition to the female sex hormone... 

Combined oral contraceptives (COCs) are helpful, especially when prostaglandin inhibition fails. COCs are thought to relieve dysmenorrhoea by inducing endometrial thinning and inhibiting ovulation, resulting in low levels of uterine prostaglandins. 

Q7 Combined oral contraceptives contain synthetic oestrogens and progestogens which inhibit FSH and LH release. These compounds inhibit both ovulation and the secretory phase of endometrial growth. Since they are inhibitors of ovulation, they are able to diminish the symptoms of dysmenorrhoea and premenstrual syndrome, which both appear to be related to the menstrual cycles in which ovulation occurs. 

Combined oestrogen-progestogen oral contraceptives have been extensively used since 1956. The principal mechanism is inhibition of ovulation (4, above) through inhibition of gonadotrophin secretion from the h3 othalamus. In addition the endometrium is altered, so that implantation is less likely (7, above) and cervical mucus becomes more viscous and impedes the passage of the spermatozoa (5, above). 

Oral dirithromycin reduced the mean ethinylestradiol 24-hour AUC and increased its oral clearance in women using an oral contraceptive (3). However, since there was no effect on inhibition of ovulation, the clinical importance of this interaction may be negligible. 

Currently, the most effective method to prevent conception is by oral steroid hormone treatment (Figure 34-9) to inhibit or modify the cyclic changes in endogenous reproductive hormones. Two effective types of oral contraceptives are used with proven success one to prevent ovulation, the other to prevent implantation. 

Oral contraceptives decrease free testosterone levels by increasing sex hormone-binding globulin, leading to a decrease in sebum production, and they inhibit the ovarian production of androgens by suppressing ovulation. 

---