[Lotus]

Antagonism between estrogen and androgen hormone action is elegantly exemplified by the sexual dimorphism of breast development; full mammary gland growth and maturation occurs in females due to the dominance of estrogen action and does not occur in males due to the dominance of androgen action. Perturbations of sex-specific hormone levels can cause abnormal breast development in males and females. This also occurs at the receptor level, whereby the mammary gland fails to develop in females lacking a functional estrogen receptor α (ERα) and fully develops in males lacking a functional androgen receptor (AR).