Table 1.

Characteristics of the studies included in the systematic review and meta-analysis

Author, year (Ref)	Country	Number of participants	Age (yr) (PCOS vs. controls)	BMI (kg/m2) (PCOS vs. controls)	Sample (unit)
Hamed et al. , 2022 (25) *	Egypt	PCOS: 60 Control: 24	28.42 $\pm$ 4.34 30.13 $\pm$ 3.26	31.32 $\pm$ 4.80 25.43 $\pm$ 1.44	Serum (pg/ml)
Faeza et al. , 2023 (26) *	India	PCOS: 40 Control: 40	26.7 $\pm$ 2.6 27.1 $\pm$ 3.1	25.07 $\pm$ 0.56 27.1 $\pm$ 0.62	Serum (ng/ml)
Wang et al. , 2021 (27) *	China	PCOS: 200 Control: 150	28.5 $\pm$ 10.1 29 $\pm$ 12.1	N/A	Serum (mg/ml)
Varli et al. , 2021 (22) *	Turkey	PCOS: 41 Control: 40	27.7 $\pm$ 3.6 29.0 $\pm$ 3.7	24.8 $\pm$ 4.2 23.7 $\pm$ 5.0	Serum (mmol/L)
Ali et al. , 2021 (28) **	Iraq	PCOS: 45 Control: 40	29.3 $\pm$ 5.7 29.5 $\pm$ 5.2	30.1 $\pm$ 4.2 29.3 $\pm$ 5.1	Serum (ng/ml)
Demir et al. , 2021 (29) *	Turkey	PCOS: 44 Control: 40	26.41 $\pm$ 5.036 28.23 $\pm$ 5.09	24.07 $\pm$ 2.97 24.7 $\pm$ 3.7	Serum (ng/ml)
Taskin et al. , 2016 (18) *	Turkey	PCOS: 32 Control: 26	24.72 $\pm$ 4.30 26.85 $\pm$ 5.06	23.83 $\pm$ 3.55 22.16 $\pm$ 2.47	Serum (mmol/L)
Sahin et al. , 2015 (21) *	Turkey	PCOS: 54 Control: 48	22.2 $\pm$ 4.2 21.5 $\pm$ 4.5	30.0 $\pm$ 7.5 29.7 $\pm$ 5.6	Serum (ng/ml)
Alp et al. , 2015 (15) *	Turkey	PCOS: 55 Control: 35	25.95 $\pm$ 5.61 28.14 $\pm$ 6.76	24.03 $\pm$ 5.06 22.34 $\pm$ 3.22	Serum (ng/ml)
Binnetoglu et al. , 2014 (30) *	Turkey	PCOS: 37 Control: 28	25 $\pm$ 7.8 28 $\pm$ 6.17	25.17 $\pm$ 4.9 22.81 $\pm$ 3.6	Plasma, Serum (pg/ml)
Ademoglu et al. , 2014 (11) **	Turkey	PCOS: 55 Control: 28	25.1 $\pm$ 5.6 26.2 $\pm$ 4.9	27.4 $\pm$ 6.8 21.0 $\pm$ 2.8	Plasma, Serum (pg/ml)
Deniz et al. , 2012 (9) *	Turkey	PCOS: 30 Control: 30	23.56 $\pm$ 4.80 23.16 $\pm$ 3.66	25.03 $\pm$ 0.86 24.43 $\pm$ 0.50	Serum (ng/ml)
*Case-control study, **Cross-sectional study. BMI: Body mass index, PCOS: Polycystic ovary syndrome