Examiners use different criteria for the diagnosis of the syndrome. These are mainly: [3]

1. National Institute of Child Health and Human Development (NICHD) / National Institute of Health (NIH)
2. European Society of Human Reproduction and Embryology (ESHRE)/American Society for Reproductive Medicine (ASRM)
3. Androgen Excess Society AES criteria. 

BIOMARKERS

Figure 2. Cartoon representation of Biomarkers

Biomarkers are molecules of biological relevance found in body fluids and tissues that can indicate standard or abnormal processes or conditions. It is also used to check the body's response to the treatment of a disease or condition. [4] They can be indicators of the body's normal biological processes, pathogen invasion or relating to response to an intervention. Their importance in clinical trials has been well characterised and repeatedly shown to predict relevant clinical outcomes across various treatments and populations correctly. 

Biomarkers confirm the presence of a disease condition or can help identify future comorbidity; therefore, selecting the correct and specific biomarkers are essential in diagnosis. 

Few terms related to biomarkers:

Sensitivity: Sensitivity is the probability that the test results of the biomarker will be positive when the disease is actually present. It is a measure of the true positive that a biomarker can show for a given disease.

Specificity: Specificity is the probability that the test results of the biomarker will be negative when the disease is not present. It is a measure of the true negative that a biomarker can show for a given disease.

FEMALE REPRODUCTIVE SYSTEM

Figure 3. Diagrammatic representation of female reproductive system

Parts of the female reproductive system

. The female reproductive system is composed of 

1. Ovaries
2. Fallopian tubes
3. Uterus
4. Vagina
5. Vulva

 Adjacent structures to the uterus consisting of ovaries and fallopian tubes, constitute the adnexa.

Ovaries

1. Location: Two in number, located on the sides of the uterus.
2. Ovaries are the site of gametogenesis i.e., the production of gametes and secretion of sex hormones.
3. There are two prominent regions in the ovaries: 
   

                 1) Outer cortex: The site where follicles begin to develop.

                 2) Inner Medulla: Enriched with blood vessels and connective tissues.

4. Each ovary is about the size and shape of an almond. Eggs develop and mature in the ovaries, which are released monthly in the reproductive years.
5. In premenopausal women, the ovaries produce numerous follicles a month, with one dominant follicle maturing and undergoing ovulation.

 Fallopian Tubes

1. Fallopian tubes are the major adnexal structures. 
2. Fallopian tubes allow oocytes to travel from the ovaries into the uterine cavity. 
3. The part of each tube closest to the ovary contains fimbria: finger-like projections that help move the expelled oocyte further into the tube—the fimbria transitions into the ampulla, the part of the tube with the widest lumen. 
4. The ampulla is known as the site for fertilisation. The ampulla becomes the isthmus as the lumen narrows and projects towards the uterus.

 Uterus

1. The uterine region is divided into corpus (body) and cervix. 
2. Corpus consists of the fundus, while the inferior portion adjacent to the cervix is called the isthmus/lower uterine segment. 
3. The uterus is a layered structure primarily composed of three distinct layers: the endometrium, myometrium, and the serosa. 

         1) Endometrium: lines the uterine cavity, and its thickness and structure vary with hormonal stimulation. 

         2) Myometrium: consists of smooth muscle fibers and is the middle and thickest layer of the uterine wall. 

         3) Serosa: The outermost lining of the uterus. [6]

 Vagina

1. The vagina is a flexible, fibromuscular tubular structure extending from the vestibule to the uterine cervix. The anterior vagina lies adjacent to the posterior bladder wall, while the posterior vagina borders the anterior rectum.

Vulva 

1. The vulva describes the external female genitalia: labia majora, labia minora, clitoris, vulvar vestibule, urethral meatus, and vaginal orifice.
2. The labia majora are lateral to the labia minora, fusing anteriorly to make up the mons pubis (a layer overlying the pubic symphysis). The vulvar vestibule is the area medial to the labia minora and is the location of the urethra and vaginal openings.

CYSTS

Figure 4. Cross sectional view of ovary with cysts

What are cysts?

The morphology of cysts includes membranous sac-like pockets that contain fluids, air or other substances. These can vary in size based on various factors such as location, type of cysts, and severity of the disease. If they cause pain or discomfort or are inflated or infected, they must be treated as soon as possible, as it could get life-threatening.

What are Ovarian Cysts?

During ovulation, fluid-filled sacs known as ovarian cysts can form on one or both ovaries, and approximately 20% of women develop at least one pelvic mass in their lifetime. Functional and benign cysts are usually found, which do not need surgical intervention. However, complications such as pelvic pain, cyst rupture, blood loss, and ovarian torsion whose cause can be attributed to ovarian cysts and that require prompt management.

Risk factors for ovarian cyst formation include: [9]

1. Infertility (problems with conceiving) and issues in pregnancy
2. Hypothyroidism: Excess of thyroid hormone being released due to an overactive thyroid gland.
3. Development of fetal ovarian cysts.

What is a polycystic ovary?

Polycysts (poly meaning many; cyst) as seen in the case of Polycystic Ovarian Syndrome, and are formed due to excess androgen production. The ovaries become enlarged and are filled with multiple cysts [10].

APTAMERS

Figure 5. Representation of aptamer folding

What are aptamers?

The term ‘aptamer’ was derived from combining the Latin word ‘aptus’ (to fit) and the Greek word ‘meros’ (part). 

Aptamers are short stretch of single-stranded oligonucleotides that bind specifically to target molecules (in our case, biomarkers of PCOS). They are generally shorter than 40 nucleotides(nts), but the length can vary depending on use and design. The high specificity of aptamers to bind to biomolecules is because of the shape-forming feature of the single-stranded oligonucleotides, making them useful analogues of antibodies. 

Single-stranded RNAs can fold into multiple tertiary structures depending on their sequence, hence giving aptamers an upper edge to be molecular mimics of proteins.

In addition, aptamers are shown to have additional features, such as robustness against both reducing conditions and heat denaturation. They can even be inactivated under physiological conditions by hybridization with antisense oligonucleotides, and thus, design of an antidote molecule is quite simple and easy to make.

LIGHT-UP APTAMERS

Figure 6. Light-up aptamer

This class of aptamers is known to show fluorescence in the presence of a fluorogenic molecule.

Fluorogens are molecules free to rotate about their axis; however, when their movement is restricted, they dissipate the excess energy in the form of fluorescence or heat.

Light-up aptamers use this property of fluorogens to restrict their movement, which is shown to emit fluorescence. They have been used in tagging RNAs, thus providing a simple approach for a protein-free live-cell imaging of RNAs by fluorescence. Being composed of RNA, modulation using different techniques, such as cycles of transcriptions, selection, and reverse transcription, provides a huge advantage over GFP. Several types of well-crafted light-up aptamers include Broccoli, Spinach, Spinach2, and iSpinach.

SELEX

Figure 7. SELEX cycle

Aptamers are generated by an in vitro molecular evolution method known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX). SELEX experiments can be conducted against various target molecules or elements, such as small compounds, proteins, nanoparticles, or live cells.