The luteal phase is the stage of a woman’s cycle beginning at the time of ovulation and ending when the menses begin. During this time, the follicle undergoes its dramatic transformation into the corpus luteum, which will secrete predominantly progesterone. The distinct shift in the hormonal climate during the luteal phase alters the structure of the endometrium, allowing the embryo to successfully implant. Without a healthy luteal phase implantation can’t happen, and so effective luteal phase defect treatment is crucial to restore healthy fertility.

There is a misconception that a follicle develops in a single menstrual cycle. Although the luteal phase typically lasts 2 weeks, ovulation and the formation of the corpus luteum are the culmination of a much longer period of preparation. The process of folliculogenesis begins around 375 days before ovulation with the recruitment of primordial follicles that have been dormant since birth.

At birth, the primordial follicles contain the oocyte surrounded by granulosa cells. Once recruited, it takes more than 300 days for a follicle to complete the preantral period, during which time granulosa cells replicate and theca cells are recruited. When these follicles finally reach the beginning of the 28-day cycle that they have been preparing for, they will compete for follicle-stimulating hormone to become the dominant follicle. During the first 2-week period of the cycle, theca cells produce androgens, and granulosa cells aromatize androgens to estrogen.

During the follicular phase, estrogen stimulates proliferation of endometrial cells. In the luteal phase, progesterone differentiates the endometrial stroma, increases glandular secretions, and changes the pattern of uterine proteins to produce an environment supportive of early embryonic development. Progesterone is also anti-inflammatory and induces relaxation of the myometrium.

Formation of the Corpus Luteum and the Luteal Phase

By the end of the follicular phase, the luteinizing hormone surge results in ejection of the oocyte and transforms the remaining follicle into the corpus luteum; small and large luteal cells are formed from theca and granulosa cells, respectively. The small luteal cells secrete small amounts of progesterone and convert cholesterol to androgens. The large luteal cells produce 6 to 8 times the progesterone of the theca cells and aromatize androgens to estrogen.

Factors Influencing Luteal Cell Function

Membranes of luteal cells are in proximity to capillaries. This provides for the high metabolism of the corpus luteum, which consumes 2 to 6 times more oxygen per unit weight than the liver, kidney, or even the heart. As you can imagine, the promotion of circulation is essential for healthy luteal cell hormone production.

Production of progesterone depends on mitochondrial function in the luteal cells and a host of hormonal factors. It also depends on availability of its precursors cholesterol and pregnenolone. Hormones that specifically support the growth or function of the corpus luteum include luteinizing hormone, growth hormone (GH), insulin-like growth factor 1, prostaglandin E2, and prostacyclin.1

Thyroid and Adrenal Function and Relationships to Progerstrone

Thyroid function is essential for development and growth of the follicle. Thyroid hormones work synergistically with follicle-stimulating hormone to develop healthy granulosa cells. Thyroid hormones have also been found to augment steroidogenesis from granulosa and large luteal cells.2

The adrenal glands produce some progesterone, which they use mainly in the synthesis of cortisol. In situations of stress where high levels of cortisol are produced by the adrenals, more progesterone is also needed as a substrate. The adrenals will then shunt additional pregnenolone down the cortisol pathway, reducing the amount available for progesterone production. This is why stress reduction and adrenal support are key for women who have luteal phase or progesterone deficiencies.

Diagnotics, Signs, and Symptoms

There are several diagnostic markers that we can use to detect luteal phase deficiencies. These include the following:

Treatments - Natural Fertility Boosters

General nutrition is important. A whole-foods diet should be practiced, including plenty of high-quality protein and avoidance of hormone disruptors. Foods rich in healthy fats such as avocados, nuts and seeds, free-range organic eggs, and extra-virgin coconut oil provide precursors for steroid hormones. Because folliculogenesis is a prolonged process, nutrition in the year before a cycle can affect the luteal phase.

Natural fertility boosters to be given during the entire cycle include the following:

Supplements to be Given in the Luteal Phase Only of the Cycle Include the Following:

If Indicated, the Following Supplements are Recommended:

A Healthy Luteal Phase Delivers

A healthy luteal phase is an essential part of a woman’s fertility with its crucial role in the implantation of the embryo and the maintenance of early pregnancy. In the naturopathic clinic, we can promote a healthier luteal phase by cultivating high-quality luteal cells from their very beginning, enhancing the factors that influence the function of the corpus luteum, and supporting optimal hormonal balance.


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