I am not a biology student, just a curious person. To be specific, I'm talking about female humans. I know that it might apply to other mammals.

What controls the size of breasts?

I have heard about progesterone hormone.

  • Is it just progesterone?

  • Are there any other factors?

  • I have seen a movie in which couple talks about breast size increases after sex. Is it true?

Can somebody give more info on this?

  • $\begingroup$ Prolactin may be a good candidate. $\endgroup$
    – nico
    Mar 23, 2013 at 18:53

2 Answers 2


The known factors seem to be mainly oestrogen and genetic (although I haven't been able whatsoever to find detail on what genes):

Manning et al (1997): Breast asymmetry and phenotypic quality in women. Evolution and Human Behavior, 17 (2): 129–143.

Our data support the thesis that mammotropic hormones, particularly estrogen, are harmful because they suppress the immune system. Heavy women with high levels of body fat produce more estrogen and, therefore, bigger breasts. However, more estrogen leads to an increase in breast asymmetry. Women with “good genes” are able to produce symmetric breasts despite the presence of large quantities of estrogen. Large and symmetric breasts are therefore honest signals of high phenotypic quality in women.


The first signs of breast growth begin as a girl reaches her teens. The fat in the connective tissues starts to accumulate when the ovaries begin to secrete (express) estrogen. The breasts will then grow. Also, the duct system begins to grow. These breast changes often occur at the same time as pubic hair and armpit growth.

After menstruation and ovulation, maturing begins in the breasts with the formation of secretory glands near the milk ducts. With the development of many glands, lobules, and breasts that continue to mature and grow, the duct system and breasts also continue to develop. Each woman's breast growth rate is different. In the end it's estrogen and the amount of fat that accumulate in the breast, that are largely responsible for the size of the breasts.

  • 1
    $\begingroup$ You've been busy! Unfortunately this doesn't seem to provide any new information and most of it is not actually answering the original question. Please focus on providing high quality answers rather than quantity. $\endgroup$
    – tyersome
    Dec 24, 2021 at 2:11

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