The body has its own unique way of balancing levels of estrogen as and when needed. For example, estrogen levels need to increase for the endometrial wall to thicken, and they are at their peak just before ovulation. For successful ovulation to occur, estrogen levels need to taper drastically.
If this does not occur, the ovum is not released and it remains within the ovary. This leads to many complicated health issues, including infertility.
Then there's estrogen and weight control. Distribution of body fat is gender-specific. Females having fat depots around their thighs, hips, and butts, and males have more visceral fat. After menopause, however, there is redistribution of fat, and women tend to accumulate more fat around the middle.
The risk of obesity is significantly lower in women than men — in premenopausal women, that is. But after menopause, these risks increase and are similar to the male obesity risk. This is because estrogen has an influence on the formation of fatty tissue and adipose metabolism (fat metabolism).
This is because estrogen production is carried out in the adipose tissue, which starts a vicious cycle within females after menopause. Estrogen imbalance produces more adipose tissue, and this adipose tissue produces more estrogen.
Last but not least, there's the connection between estrogen and cancer — specifically, breast cancer and uterine cancer. Since estrogens are responsible for the thickening of the endometrium, they have a cell-proliferating effect. If they show this effect on other parts of the body, their activity leads to the development of cancers.
The relation of estrogen and breast cancer is also dependent upon weight. Obese post-menopausal women tend to be more at risk of developing breast cancer than women with normal weight.
Excess body fat (greater than 28 percent) is also one of the causes of a condition called "estrogen dominance," which can increase the risk of breast cancer among other issues like decreased sex drive, breast swelling and tenderness, mood swings, and further weight gain.