By Rut Gómez de Segura (Gynaecologist – Reg. No. 28/2908776).
Estrogens are hormones commonly associated with femininity. However, their role goes far beyond influencing the development of sexual characteristics. They participate in key aspects of female fertility, such as regulating the menstrual cycle, triggering ovulation, and preparing the uterus for pregnancy.
In fertility treatments, maintaining a proper estrogen balance is essential for ensuring that the endometrium becomes receptive and ready to host the embryo — a fundamental step for achieving pregnancy.
Estrogens are a group of sex hormones mainly produced in the ovaries, though smaller amounts can also be synthesized in the adrenal glands and adipose tissue. Within this group, estradiol is the most active and plays the most significant role in female fertility.
During the first half of the menstrual cycle, estradiol levels gradually increase as the ovarian follicles mature. This rise stimulates endometrial growth, making it thicker and richer in blood vessels. Proper endometrial preparation is crucial to allow successful embryo implantation when the time comes.
In fertility treatments such as in vitro fertilization (IVF), estrogens have a key function: preparing the uterus to receive the embryo. During ovarian stimulation, estrogen levels are carefully monitored, as they indicate how the body is responding to treatment.
Later, in the endometrial preparation phase, especially during frozen embryo transfer cycles, estradiol is administered in a controlled manner to reproduce the hormonal conditions of a natural cycle. If ovarian stimulation develops properly and estrogen levels are optimal, the endometrium acquires the required thickness and structure for embryo implantation. Conversely, if levels are too low, the endometrial lining may remain thin or unreceptive, reducing the chances of success.

The role of estrogens extends beyond fertility. They contribute to bone density maintenance, cholesterol regulation, mood balance, and cardiovascular health. When estrogen levels decline, such as during menopause or in certain hormonal disorders, symptoms like:
However, excessively high estrogen levels — associated with medical conditions like polycystic ovary syndrome (PCOS) or certain hormone therapies — may also lead to hormonal imbalances, including irregular cycles or fluid retention.

A healthy diet can positively influence the natural regulation of estrogens. Some foods contain phytoestrogens — plant-based compounds with a structure similar to human estrogens — which can help maintain hormonal balance.
These include:
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