The aim of the study was to investigate the changes in the clinical and biochemical parameters of adolescents on a low-carbohydrate diet in relation to their PCOS phenotype in the 3rd trimester.

Polycystic ovary syndrome (PCOS) is an endocrine-metabolic disorder characterized by menstrual irregularities, anovulation, clinical and/or biochemical symptoms of hyperandrogenism (hirsutism and/or acne), micropolycystic ovaries, and metabolic abnormalities. In addition, some clinical and laboratory phenotypic features have been defined that were not previously included in the PCOS definition criteria, but which complement the clinical picture and influence the severity and morbidity of the clinical picture. Phenotype A: HA + OD + PCOM; phenotype B: HA + OD; phenotype C: HA + PCOM and phenotype D: OD + PCOM.For adult patients, internationally recognized diagnostic criteria have been developed based on combinations of otherwise unexplained hyperandrogenism, anovulation and polycystic ovary and are covered by the Rotterdam Consensus Criteria. However, in the adolescent age group, the frequency of anovulatory cycles and associated menstrual irregularities, the frequent symptoms of hyperandrogenism and acne vulgaris in the developmental phase, the problems with testosterone measurement and the prevalence of polycystic ovarian morphology in normal adolescents complicate the diagnosis.

PCOS is a serious clinical and psychological problem for adolescent girls. Key interventions include lifestyle modification, including diet, physical activity and weight loss. These measures have been shown to alter the course of the disease in overweight and obese girls. In particular, it is known that high glycemic index carbohydrate intake and glycemic load lead to a rapid rise in blood glucose levels and increased insulin production.

It is therefore thought that reducing the amount of insulin could have a more positive effect on PCOS than the usual carbohydrates. A low-carbohydrate diet is an effective, weight-independent approach in the treatment of metabolic disorders in PCOS patients. With this in mind, this study aimed to evaluate the clinical and biochemical outcomes at month 3 after application of the low-carbohydrate diet in adolescents according to their PCOS phenotype.

Inclusion Criteria:

• at least 1 year has passed since menarche
• under 24 years old
• patients who have not received an oral contraceptive method and have given verbal and written informed consent will be included.

Exclusion Criteria:

• over 24 years old
• hyperprolactinemia, Cushing's syndrome, congenital adrenal hyperplasia, thyroid diseases
• neuromuscular, liver, pancreatic or gastrointestinal diseases
• hormonal medication such as antiandrogens, antidiabetics, glucocorticoids, insulin sensitizers or lipid regulators

The study will be conducted based on the 2018 ESHRE/ASRM guideline:

1. Oligo and/or anovulation*

2. Clinical and/or biochemical hyperandrogenism *Oligo and/or anovulation are defined as follows:

   • It is considered normal in the first year after menarche as part of the pubertal transition
   • Between 1-3 years after menarche: < 21 or > 45 days
   • 3 years after menarche - perimenopause: < 21 or > 35 days or < 8 cycles per year
   • 1 year after menarche: >90 days for each menstrual cycle
   • Absence of menstruation at the age of 15 years or 3 years after menarche.

Identification of phenotype groups:

PHENOTYPE A: HA+ OD + PCOM PHENOTYPE B: HA+OD PHENOTYPE C: HA+PCOM PHENOTYPE D: OD+PCOM.