# Soy Isoflavones and PCOS: Role in Hormonal and Metabolic Mechanisms
## 1 Introduction  
Polycystic ovary syndrome (PCOS) affects about 1 in 10 women of reproductive age, making it the most common endocrinopathy in this patient group [1, 2, 3, 4, 5]. Many women with PCOS remain undiagnosed or are misdiagnosed, and thus treatment is often delayed [5]. The importance and role of diet, functional foods, supplementation, or properly selected physical activity is also often overlooked or marginalised during the treatment of PCOS [1, 2, 3, 4, 5]. The role of soy isoflavones, an example of functional foods, is increasingly highlighted in the context of diseases and conditions, including those related to fertility, such as PCOS. Soy isoflavones are considered phytoestrogens, the active components of plants that have an affinity for oestrogen receptors [6, 7]. Depending on, among other things such as type, dose, type of oestrogen receptor they bind to, and levels of endogenous hormones, soy isoflavones can have pro-oestrogenic or anti-oestrogenic effects [8, 9, 10]. In PCOS, when oestrogen deficiency is present, soy isoflavones bind to oestrogen receptors (ER\(\theta\) and, to a lesser extent, ER\(\alpha\)), offsetting the symptoms of low endogenous oestrogen levels [11, 12]. Soy phytoestrogens also affect oestrogen levels by inhibiting the synthesisand activity of selected enzymes involved in the metabolism of both oestrogens and indrogens [11; 12; 13]. The biological activity of androgens is mainly reflected in the reduction of hyperandrogenism, which is associated with high concentrations of testosterone and dihydrotostosterone (DHT), a stronger metabolite of testosterone [13; 14; 15]. However, not all studies confirm the positive effect of soy isoflavones on testosterone, DHT, or the free androgen index [16; 17]. The significant role of soy products is also seen in the context of improving metabolic parameters (lipidogram, blood pressure, glucose and insulin levels, tissue resistance to insulin, and markers of inflammatory status). These disorders are often associated with certain PCOS phenotypes [18; 19; 20; 21; 22; 23; 24]. The scope of the effect of soy isoflavones in PCOS is therefore very wide due to the many different symptoms accompanying the syndrome, such as reproductive, dermatological, microbiotic, or metabolic disorders, as discussed in the various sections of this article [11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24]. Recently published studies indicate a link between gut microbiota and the pathogenesis and treatment of PCOS. A major role in this topic is attributed to both the involvement of soy isoflavones in modulating the composition of the host's gut microbiota and supporting its ability to convert isoflaves into forms that may support positive hormonal and metabolic effects in women with PCOS [17; 25; 26; 27].  
Therefore, the main objectives of this narrative review were (1) to review the existing literature on the relationship between soy isoflaves and their effect on hormonal and metabolic pathomechanisms associated with PCOS, (2) to analyse the potential of isoflave-microbiota interactions in modulating symptoms associated with PCOS, and (3) to indicate limitations in research and the direction of future research in this area.