4-Methylbenzylidene camphor is an ultraviolet light blocker used in cosmetics and sunscreen preparations that also has estrogenic activities. It has estrogenic activity in fish and in mammals, binding competitively to estrogen receptors and stimulating transactivation. In addition to reducing receptor sensitivity to estradiol, 4-MBC directs dose-dependent changes in the expression of estrogen receptor subtypes, progesterone receptor, and androgen receptor. This results in changes in reproductive organ and brain development in both males and females. When applied topically, it is absorbed systemically and can be detected in urine.
