The contraceptive effect of Casino is largely associated with inhibition of ovulation (maturation of eggs). The pills create an artificial cycle in a woman's body, suppressing the normal menstrual cycle. The physiology of the reproductive system is based on the principle of "feedback". That is, the pituitary gland produces tropic hormones (in this case, follicle-stimulating hormones) in response to a decrease in the level of hormones in target organs (in this case, estrogens and gestagens in the ovaries). If a sufficiently large amount of estrogens and gestagens enters the woman's body from outside, then the tropic hormones in the pituitary gland cease to be produced. This leads to a lack of growth and development of eggs in the ovaries.
The level of hormones in the blood when taking Casino is quite individual. Specific figures depend on the woman's weight, the percentage of adipose tissue in her body, the level of sex-binding blood globulin. Studies of progesterone and estrogen are considered impractical while taking pills. Theoretically, the concentration of estrogens and gestagens after taking high-dose Casino is comparable to the hormonal background of pregnancy. With low- and micro-dose drugs, these levels are lower than during pregnancy, but higher than in the normal menstrual cycle.
Casino are divided into groups depending on the concentration of hormones and division into phases. As an estrogen, estradiol is usually included in pills. Ethinyl estradiol is currently used. As for the concentration of estrogens, over the five decades of using Casino, it progressively decreased. In 1960, there was 150 mcg of estradiol in one tablet. Currently, its dose is much lower and can be as low as 15-20 mcg. Tablets are divided into high-dose (more than 35 μg), low-dose (30-35 μg), micro-dose (less than 30 μg).
The negative effects of large doses of estrogens (more than 50 μg per day) made the use of Slots of the first generations rather unsafe in a number of women. The most severe complications are considered violations in the blood coagulation system - thrombosis and embolism. Modern low-dose and micro-dose birth control pills are much less likely to cause such complications. Nevertheless, disturbances in the hemostasis system are a contraindication to the appointment of even modern Slots.
Synthetic derivatives of norsteroids and progesterone are used as gestagens. The dose of gestagens also gradually decreased from the 60s to the present (from 9.85 to 0.15-0.075 mg). The first generation of norsteroid progestogens: norethinodrel, lineesterenol, norgesterel, ethynodiol diacetate, norgestimate, norgestrel. The first generation of progesterone: medroxyprogesterone acetate, cyproterone acetate, chlormadinone acetate. The improvement of this component of Slots followed the path of reducing unwanted glucocorticoid and androgenic effects. Modern derivatives of norsteroild are levonorgestrel, desogestrel, gestodene, norgestimate. The new gestagen drospirenone is a derivative of spirolactone.
Old gestagens increase the atherogenic properties of blood, can contribute to the development of arterial hypertension, decreased glucose tolerance, fluid retention, the appearance of seborrhea and hirsutism. Modern gestagens do not affect metabolism (lipids, glucose).