The role of intraovarian regulators in the aetiology of polycystic ovarian syndrome

Hypothalamic-pituitary, ovarian and adrenal contributions to polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a prevalent heterogeneous disorder linked with disturbances of reproductive, endocrine and metabolic function. The definition and aetiological hypotheses of PCOS are continually developing to incorporate evolving evidence of the syndrome, which appears to be both multifactorial and polygenic. The pathophysiology of PCOS encompasses inherent ovarian dysfunction that is strongly influenced by external factors including the hypothalamic-pituitary axis and hyperinsulinaemia. Neuroendocrine abnormalities including increased gonadotrophin-releasing hormone (GnRH) pulse frequency with consequent hypersecretion of luteinising hormone (LH) affects ovarian androgen synthesis, folliculogenesis and oocyte development. Disturbed ovarian-pituitary and hypothalamic feedback accentuates the gonadotrophin abnormalities, and there is emerging evidence putatively implicating dysfunction of the Kiss 1 system. Within the follicle subunit itself, there are intra-ovarian paracrine modulators, cytokines and growth factors, which appear to play a role. Adrenally derived androgens may also contribute to the pathogenesis of PCOS, but their role is less defined.

Extra- and intra-ovarian factors in polycystic ovary syndrome: impact on oocyte maturation and embryo developmental competence

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common metabolic dysfunction and heterogeneous endocrine disorder in women of reproductive age. Although patients with PCOS are typically characterized by increased numbers of oocytes retrieved during IVF, they are often of poor quality, leading to lower fertilization, cleavage and implantation rates, and a higher miscarriage rate.

METHODS

For this review, we searched the database MEDLINE (1950 to January 2010) and Google for all full texts and/or abstract articles published in English with content related to oocyte maturation and embryo developmental competence.

RESULTS

The search showed that alteration of many factors may directly or indirectly impair the competence of maturating oocytes through endocrine and local paracrine/autocrine actions, resulting in a lower pregnancy rate in patients with PCOS. The extra-ovarian factors identified included gonadotrophins, hyperandrogenemia and hyperinsulinemia, although intra-ovarian factors included members of the epidermal, fibroblast, insulin-like and neurotrophin families of growth factors, as well as the cytokines.

CONCLUSIONS

Any abnormality in the extra- and/or intra-ovarian factors may negatively affect the granulosa cell-oocyte interaction, oocyte maturation and potential embryonic developmental competence, contributing to unsuccessful outcomes for patients with PCOS who are undergoing assisted reproduction.

Hyperexpression of epidermal growth factor receptors in granulosa cells from women with polycystic ovary syndrome

OBJECTIVE

To compare the localization and quantitation of epidermal growth factor (EGF) receptor in granulosa cells from women with normal and polycystic ovaries.

DESIGN

Controlled, comparative study.

SETTING

Academic research laboratory.

PATIENT(S)

Forty-two women with normal or polycystic ovaries who attended our facility for the recovery of their immature or mature oocytes or for therapeutic purposes.

INTERVENTION(S)

Patients underwent intravaginal ultrasound-guided oocyte retrieval or laparoscopic follicular aspiration with or without prior stimulation.

MAIN OUTCOME MEASURE(S)

Quantitation of EGF receptor in granulosa cells.

RESULT(S)

Granulosa cells from polycystic ovaries expressed significantly higher levels of EGF receptor than granulosa cells from normal ovaries. In contrast with patients who were treated with clomiphene citrate, those who were treated with gonadotropins showed low levels of the receptor. However, the levels of the receptor in granulosa cells were not correlated with circulating levels of LH, FSH, progesterone, or E2. Immunolabeling of EGF receptor was confined to the cell membrane of granulosa cells. This receptor was fully functional, mediating the ligand-induced inhibition of E2 production in culture.

CONCLUSION(S)

These results provide further evidence supporting a possible role of EGF/transforming growth factor-alpha in the aberration of ovarian function in polycystic ovary syndrome.