Leptin levels in women with unexplained infertility: A systematic review and meta-analysis

Table 1 Main characteristics of studies included in the meta-analysis

Ref.	Region	Study design	Method	BMI (kg/m2)		Age, years		Sample size		Leptin (mean + SD), ng/mL		LH/FSH ratio
				UI	Controls	UI	Controls	UI	Controls	UI	Controls
Tafvizi and Masomi[20], 2016	Iran	Case–control	EIA	23.6 ± 0.27	23.66 ± 0.33	29.3 ± 4.2	31.03 ± 3.76	40	30	31.20 ± 2.83	24.89 ± 2.94	0.85
Al-Fartosy et al[21], 2019	Iraq	RCT	EIA	22.3 ± 3	21.7 ± 1.4	29.45 ± 6.38	30.92 ± 5.90	63	33	28.4 ± 1.3	27.2 ± 2.3	0.61
Kamyabi and Gholamalizad[22], 2015	Iran	Case-control	EIA	24.84	22.26	30	29	30	30	27.83 ± 25.29	31.27 ± 11.02	NR
Kumari et al[11]1, 2017	Indian	Case-control	EIA	24.1 ± 3.9	24.31 ± 3.19	29.53 ± 4.43	29.58 ± 4.01	120	109	68.9 ± 2.46	37.5 ± 1.84	0.85
Baig et al[23], 2019	Pakistan	Case-control	RIA	NR	NR	NR	NR	235	205	35.32 ± 0.9	37.11 ± 1.19	2.16
Demir et al[19], 2007	Turkey	PCS	RIA	25	24.5	29.3	28.9	27	30	7 ± 1	3.4 ± 1	1.17

¹The serum leptin level in the original study was measured in pg, and converted to ng using the standard method.

BMI: Body mass index; EIA: Enzyme-linked immunosorbent assay; FSH: Follicle-stimulating hormone; LH: Luteinizing hormone; NR: Not reported; PCS: Prospective comparable controlled study; RIA: Radioimmunoassay; RCT: Randomized control trial; SD: Standard deviation; UI: Unexplained infertility.