Notes on Ovary Structure and Function

Introduction to the Ovary

  • The structure of the ovary:
    • Understanding the ovary requires knowledge of its normal physiology.
    • The functional unit of the ovary is called the follicle.

The Follicle Structure

  • A follicle consists of three main components:
    • Oocyte (the egg): the female gamete.
    • Granulosa cells: surround the oocyte and are crucial for hormone production.
    • Theca cells: located outside the granulosa cells, also important for hormone production.

Hormonal Regulation

  • Key hormones involved in ovarian function:

    • Luteinizing Hormone (LH):
    • Stimulates the theca cells to produce androgens.
    • Follicle Stimulating Hormone (FSH):
    • Stimulates the granulosa cells to convert androgens to estrogens (particularly estradiol).

  • Function of estradiol:

    • It bathes the oocyte and assists in its maturation.
    • Additionally promotes the proliferative phase in the endometrium, preparing for potential implantation after ovulation.

The Menstrual Cycle Phases

  • Following ovulation, the corpus luteum forms from the residual follicle:
    • Corpus Luteum: secretes primarily progesterone post-ovulation, preparing the endometrium for implantation.
    • Can lead to a hemorrhagic luteal cyst if bleeding occurs within it, which can mimic a mass in the ovary.

Degeneration of Follicles

  • Follicles can degenerate and become cystic:
    • Most women may have one or a few degenerative follicular cysts in their ovaries.

Polycystic Ovarian Disease (PCOD)

  • A specific disorder characterized by multiple follicular cysts:
    • Caused by a hormonal imbalance with increased LH and low FSH.
    • The LH to FSH ratio is greater than 2, which is a key diagnostic indicator.
Understanding the Pathophysiology of PCOD
  • Increased LH results in:
    • High androgen levels from the theca cells.
    • Androgens lead to symptoms including hirsutism (male-pattern hair growth).
    • Conversion of androgens to estrone in adipose tissue leading to:
    • Increased levels of estrone.
    • Feedback inhibition on FSH production, reducing estrogen production by granulosa cells.
  • Consequence of the hormonal imbalance:
    • Inability of follicles to mature leads to degeneration and cyst formation, which is the classical picture of PCOD.

Clinical Presentation of PCOD

  • Common features in an ovulatory woman:
    • Obesity: associated with high estrone production.
    • Infertility: due to anovulation.
    • Oligomenorrhea: irregular menstrual cycles.
    • Hirsutism: increased male-pattern hair distribution.

Long-term Complications of PCOD

  • Patients can develop:
    • Insulin resistance leading to a risk of Type 2 diabetes mellitus after many years.
    • Increased risk of endometrial carcinoma due to high estrone levels from chronic estrogen exposure.
    • Higher lifetime estrogen exposure correlates with increased risk for endometrial carcinoma.

Conclusion of Ovary Discussion

  • Summary of non-neoplastic aspects of the ovary prepares for the next section on ovarian tumors.