Development of the ovaries begins in intrauterine life, as early as the 3^rd weeks of gestation, primordial germ cells appear in the endoderm of yolk sac migrate along the dorsal mesentery to the urogenital ridge by amoeboid movement. As shown in Figure 2, by the 8^th weeks, the primitive germ cells undergo multiple rapid mitotic divisions and get differentiated into oogonia, number of oogonia reaches its maximum at 20^th weeks. The mitotic division gradually ceases and the majority enters into the prophase of first meiotic division are called primary oocytes. These primary oocytes are surrounded by flat cells (granulosa cells) and are called primordial follicles. At birth these oogonia get replaced by primary oocytes; hence there are no more mitotic divisions. Thus all those primordial follicles with primary oocytes in the ovary of newborn female are getting arrested in the diplotene stage prophase of first meiotic division till puberty. At puberty, now the arrested primary oocyte with surrounding follicular cells (also known as primordial follicle) gets developed into mature Graafian follicle (measures its size about 12 - 16 mm) through the development of growing follicle, primary follicle(with multilayered follicular cells) and secondary follicle (primary follicle with antrum) under the control of FSH secreted by anterior pituitary gland. The

mature Graafian follicle is spherical or ovoid in shape contains liquor folliculi. The lining of it consists of two layers, the theca cells layer and granulose cell layer [10]. Theca is responsible for the production of ovarian hormones; ie; estrogen, progesterone and sometimes extended to the production of androgens. Granulosa cells secrete a clear fluid composed of protein, known as liquor folliculi, which contains ovarian hormone estrogen. Until puberty, most primordial follicles in the ovary undergo retrogression by a process termed as follicle atresia. During reproductive age, several follicles tend to develop in each menstrual cycle. In response to FSH, small gap junctions (to provide a pathway for nutrition and metabolic interchange) develop between the granulosa cells and the oocyte. Among several follicles developing on both ovaries, one follicle grows faster than the rest and generates more FSH receptors and estrogen. The raised level of estrogen stimulates LH receptors in the theca cells as well as gives negative feedback to the anterior pituitary gland leading to progressive fall in FSH level, due to which only developed follicle remains and undergoes ovulation, rest all follicles get atrophied [27] [28].

The oogenesis process is completely different than that of a normal cycling fertile woman. During folliculogenesis, the individual conversion of the primordial follicle to primary follicle does not depend upon the gonadotropins [13] [29] [30]. Due to the functional deficiency of the endogenous action of FSH, the follicular growth is frustrated at different phases of maturation (2 - 10 mm in diameter) [5]. In the obese patient, the fat (adipose tissue) secretes leptin (also secreted by ovarian follicle), adiponectin and cytokines which interferes the insulin signaling pathways in liver and muscles which results in insulin resistance and hyperinsulinemia. Insulin stimulates the LH to cause thecal hyperplasia and secretes androgens, testosterone, and epi-androstenedione. Due to the hyperactivity of thecal cell and increase level of androgens, testosterones, and epi-androstenedione, accelerate the generation of estrogen in granulosa cells [31] [32] [33]. There is defective FSH induced aromatization of androgens to estrogens; therefore follicular microenvironment is more androgenic rather than estrogenic. Androgen also suppresses the growth of the dominant follicle and prevents apoptosis of smaller follicles which are normally destined to disappear in the late follicular phase; hence multiple immature follicles remain in the ovary. Unless there is estrogenic follicular microenvironment, follicular growth, maturation, and ovulation cannot occur. Epi-androstenedione converts to estrone in the peripheral fat, leads to a rise in estrogen and inhibin level, in turn, causing tonically elevated LH without any surge. LH surge is essential for ovulation to occur. In PCOs patient, a spike increase of LH can also cause early maturation of granulosa cells rather than the organized signaling to continue follicular development from the primary to the secondary than to graffian follicular stage [34]. Estrone level is prompted whereas estradiol remains normal, resulting in the raised ratio of estrone/estradiol.

Hyperandrogenism due to insulin resistance and hyperinsulinemia in PCOs patient occurs due to following two ways- by stimulating the synthesis of androgen from ovary along with LH [17] or by decreasing the sex hormone binding globulin (SHBG) [35]. So hyperandrogenism again lowers the level of hepatic sex hormone binding globulin, hence level of free testosterone gets raised. Clinically hyperandrogenism is primarily manifested by hirsutism, acne and male pattern alopecia [36]. Hirsutism is the male type terminal hair growth and distribution in females [37]. PCOS is a common cause of hirsutism occurring in approximately 60% of cases depending upon the race and degree of obesity [28] [36]. Hirsutism should be assessed with a standardized scoring system (Ferriman-Gallwey score) [38].

The pathogenesis is initiated from the early adolescent period; early adrenarche and early menarche are observed in a few girls. Menstrual abnormalities like oligomenorrhoea or secondary amenorrhea more than 3 months followed by menometrorrhagia are the clinical manifestation of ovarian dysfunction ie: anovulation or oligo ovulation [39]. PCOS is the most common cause of an ovulatory infertility. About 90% to 95% of women with anovulation who attends infertility clinics are diagnosed to be PCOS. But 60% of women with PCOS are found to be able to conceive within 12 months, although time to conceive is often increased [9]. In the fact that all women with PCOS are usually not entirely sterile but they do ovulate sometimes spontaneously. The ovulatory frequency has not been studied well, but few studies show that ovulation occurs in up to 32% of menstrual cycles [11]. In those with PCOS and infertility, 90% are overweight. Obesity is another independent factor which exacerbates infertility, reduces the efficacy of infertility treatment and induces a greater risk of miscarriage [39]. Currently, an active debate about the appropriate limit for body mass index for assisted reproduction therapies is going on, which gives a clear idea that in overweight women, the pregnancy success rate is reduced along with the association of risk in pregnancy [40]. Ideally, Overweight has to be optimized before conception. Age is also a factor which exacerbates infertility, so it is wise to think about family planning on time.

The diagnosis of PCOS is based on the Rotterdam criteria (Table 1). In Rotterdam,

ESHRE (European Society of Human Reproduction and Embryology)/ASRM (American Society of Reproductive Medicine), the PCOS consensus workshop group has proposed a revision of the PCOS diagnostic criteria which suggests the presence of at least two of the following criteria together with the exclusion of other etiologies (congenital adrenal hyperplasia, hyperprolactinemia, thyroid dysfunction, androgen-secreting tumors and Cushing syndrome) [21].

There is a remarkable difference between normal and polycystic ovary (Figure 3). Transvaginal ultrasound is the most widely used technique for the ultrasound assessment of PCOS. The comparison of ultrasound imaging between the normal ovary and polycystic ovary is shown in figure (Figure 4). The sonographic criteria have been subsequently modified and, therefore, the increase in ovarian volume (>10 cm³) with dense echogenic stroma due to enlargement and the

presence of multiple (12 or more) follicles each with a diameter of 2 to 9 mm sized placed peripherally along the surface of ovary giving a necklace appearance at least in one ovary [43]. It must be excluded from this rule women who use an oral contraceptive as it transforms the ovarian morphology in healthy women and probably also in women with PCO [21]. The ultrasound findings can rule out the ovarian tumor, adrenal hyperplasia or tumor and also shows endometrial hyperplasia if present. The ultrasound should preferably be performed in the early follicular phase. Laparoscopy is reserved for therapeutic purpose rather that diagnostic purpose because the diagnosis can be confirmed by ultrasound findings.

LOD is done for cases found resistant to medical therapy and who require laparoscopy for another reason (pelvic pain, adnexal mass, etc). Ovarian surface cysts are punctured up to depth 2 - 4 mm. The cysts are vaporized using monopolar cutting current. 5 - 8 punctures are made in each ovary because a larger number may favor the development of premature ovarian failure [55]. The ovarian drilling in the treatment of infertility in women with PCOS results decreased secretion of androgens and consequent reduction of peripheral aromatization of those androgens into estrone which favors the follicular growth creating estrogenic follicular microenvironment [56]. Pregnancy rates following ovarian diathermy are higher.

Clomiphene treatment should be restarted again if the patient does not regain normal ovulatory cycles after three months of ovarian drilling and the use of gonadotropins should be considered after 6 months of anovulatory cycles following the ovarian drilling procedure.

In vitro fertilization represents the third-line treatment for infertility in women with PCOS. The IVF becomes the first option in the patient with diagnosed and established bilateral tubal occlusion and/or concentration of recovered motile sperm less than or equal to 5 million. The risk of OHSS is the main complication of the high complex treatment in women with PCOS. Thus, controlled ovarian stimulation with low doses of gonadotropins is begun once the pituitary downregulation is achieved with administering of gonadotropin-releasing hormone (GnRH) analog. Exogenous gonadotropins (uFSH, rFSH, HMG) are used for ovarian stimulation. The follicular growth response is monitored by sonographic measurement of follicles, cervical mucus study, serum estradiol estimation commencing on the 8^th day of the treatment cycle. When two or more follicles are of 17 - 18 mm in diameter and level of serum Estradiol is optimum, hCG or recombinant hCG is administered to induce oocyte maturation then the oocytes are retrieved aseptically through vaginal route under ultrasonic guidance 36 hours after the hCG is given. Approximately 50,000 - 10,000 capacitated sperms are placed into the culture media containing the oocyte within 4 - 6 hours of retrieval. The egg may demonstrate the signs of fertilization (presence of two pro-nuclei in the presence of 2^nd polar body) when examined 16 - 18 hours after insemination. Only 2 - 3 fertilized ova (to prevent from multiple gestations) can be placed into uterine cavity close to fundus about 3 days after fertilization through a fine flexible soft catheter transcervically. Excess oocytes and embryos can be cryopreserved for future use. The luteal phase support to the embryo is maintained by progesterone supplement.

Treatment with metformin (insulin sensitizer) improves the metabolic syndrome by reducing all the parameters: weight, BMI (hyperinsulinemia and hyperandrogenism), BP and lipid abnormalities. Women with PCOS and hyperinsulinemia with BMI > 25 ovulate satisfactorily when clomiphene is combined with metformin. Although metformin is associated with better clinical pregnancy rates there is no evidence of better live birth rates when this drug is used alone or in combination with CC [57]. From a reproduction standpoint, there is also no benefit for its use in short (less than four weeks) or long (more than four weeks) periods prior to starting CC treatment in women with PCOS. Therefore, the use of metformin should be restricted to the treatment of glucose intolerance or type II diabetes in women with PCOS and should not be used to induce ovulation.

The effectiveness of aromatase inhibitors in the treatment of PCOS remains controversial. Although aromatase inhibitors have been used in women with PCOS as an alternative method to avoid the anti-estrogenic effect of CC on the endometrium, these compounds are not typically used in clinical practice to treat infertility in these patients. Their mechanism of action is based on reducing the peripheral conversion of androgens to estrogens in ovarian granulosa cells by blocking aromatase. Consequently, a decrease in estrogen serum levels and in its negative feedback in the hypothalamus and pituitary gland is noted, resulting in increased endogenous gonadotropin release [58]. Aromatase inhibitors are promising, and long-term studies are necessary to prove their safety.