More likely than not, you’ve never even heard of being estrogen deficient because we’re so focused on thinking about estrogen as the bad guy. Yet, estrogen, along with other hormones, plays a crucial role in the menstrual cycle and fertility.

Estrogen deficiency can have profound effects on a woman's fertility, and here's how:

• Follicular Development: Estrogen is produced by the growing follicles in the ovaries during the first half of the menstrual cycle. This phase is known as the follicular phase. Adequate levels of estrogen are necessary for the proper development and maturation of the follicle. A deficiency in estrogen can hinder the development of the follicle, and thus, decrease the chances of ovulation.

• Endometrial Growth: Estrogen is responsible for the thickening of the endometrial lining in the uterus after menstruation. This thickened lining is essential for the implantation of a fertilized egg. If estrogen levels are too low, the lining may not be sufficiently prepared for implantation, reducing the chances of a successful pregnancy.

• Ovulation: The surge in estrogen levels that occurs mid-cycle triggers a surge in luteinizing hormone (LH) from the pituitary gland. This LH surge is what prompts ovulation, or the release of the mature egg from the follicle. Without adequate estrogen, this LH surge might not occur, preventing ovulation.

• Cervical Mucus Production: Estrogen stimulates the production of fertile cervical mucus. This mucus is slippery and stretchy, and it helps sperm move through the cervix to reach the egg. If estrogen levels are low, the mucus may be less abundant or of a less fertile quality, making it more difficult for sperm to reach the egg.

• Bone Health and Overall Reproductive Health: Chronic estrogen deficiency, as seen in conditions like premature ovarian insufficiency, can lead to decreased bone density and other systemic issues. While this does not directly impact fertility, the overall health of the reproductive system can be compromised, which might influence fertility indirectly.

• Luteal Phase: While the luteal phase (the second half of the menstrual cycle) is more under the influence of progesterone, estrogen plays a supportive role. Inadequate estrogen in this phase can affect the proper function and lifespan of the corpus luteum (the remnant of the follicle after ovulation), which in turn can affect progesterone production and endometrial support.