How do contraceptives use hormones to prevent pregnancy?

Contraceptives use hormones to prevent pregnancy by inhibiting ovulation and altering the uterine lining and cervical mucus.

Hormonal contraceptives, such as the pill, patches, injections, and implants, primarily work by releasing synthetic versions of the female hormones oestrogen and progesterone. These hormones play a crucial role in the menstrual cycle and fertility. The synthetic hormones in contraceptives mimic the natural hormones in the body, tricking the body into thinking it's already pregnant, which prevents ovulation, the release of an egg from the ovaries.

The synthetic oestrogen in contraceptives works to stop the pituitary gland from producing follicle stimulating hormone (FSH) and luteinising hormone (LH). FSH is responsible for the growth and maturation of the egg in the ovaries, while LH triggers the release of the mature egg. By inhibiting the production of these hormones, ovulation is prevented, thus eliminating the possibility of fertilisation.

The synthetic progesterone, also known as progestin, thickens the cervical mucus, making it difficult for sperm to enter the uterus and reach any egg that may have been released. Furthermore, progestin also thins the lining of the uterus, making it less likely for a fertilised egg to attach and develop.

In addition to preventing ovulation and making it harder for sperm to reach an egg, hormonal contraceptives also alter the natural menstrual cycle. The steady levels of synthetic hormones prevent the mid-cycle hormone surge that would normally lead to ovulation. Instead, the hormone levels remain relatively constant, leading to a predictable withdrawal bleed (often mistaken for a period) when the hormones are stopped or reduced, depending on the type of contraceptive used.

In summary, hormonal contraceptives use a combination of synthetic oestrogen and progesterone to prevent ovulation, alter the uterine lining and cervical mucus, and regulate the menstrual cycle, thereby preventing pregnancy.