Puberty is a time of significant growth and physical changes. It usually starts between eight and 13 years old for females and between nine and 14 years old for males.
The start of menstrual periods and the development of the breast are the main changes in females. These are controlled by hormones, mainly oestrogen.
Endocrine Disrupting Chemicals (EDCs) can interfere with the normal function of hormones and may have an impact on puberty and breast development.
Starting menstrual periods early (before 10 years old) and developing breasts early (before eight years old) have been linked with an increased risk of breast cancer.
Studies have shown that girls are now starting puberty at a younger age than girls who were born in the 1970s. With puberty starting at a younger age, the exposure to oestrogen throughout life is lengthened. Prolonged exposure to oestrogen is believed to increase breast cancer risk.
So far, studies looking at EDC effects on the age at puberty have been inconclusive. More research is needed to explore the link between EDC exposure, and puberty and how this may affect breast cancer risk.
Oral contraceptives are a type of medicine that prevents pregnancy by stopping the release of eggs from the ovaries.
The combined contraceptive pill (“the pill”) contains two synthetic hormones, oestrogen and progestogen. Progestogen is a man-made form of the hormone progesterone. The “mini-pill” contains only progestogen.
Studies have shown that taking the combined contraceptive pill (“the pill”) slightly increases breast cancer risk. This risk is no longer evident 10 years after use has stopped.
Other studies suggest that progestogen-only oral contraceptives (“mini-pill”), may not be associated with breast cancer risk, however, a study from 2023 has shown a small increase in risk.
Other types of hormonal contraceptives include patches and vaginal rings, which use both oestrogen and progestogen. Injections, implants and intrauterine devices (IUDs, such as the Mirena coil) contain only progestogen.
Fewer studies have looked at the link between these types of contraceptives and breast cancer risks. However, the risks for some of these (progestogen-only) may be similar to those associated with oral contraceptives.
For more details and references, please see our Critical Windows of Susceptibility for Breast Development science review.
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