Table 1.

Summary of clinical studies on leptin levels in serum and SF of OA patients.

Author	Sample	Patients	Leptin Levels	Relation with the Disease
Dumond et al. (2003) [51]	Synovial fluid	20 OA, 2H	Detected in SF and correlated with BMI	Yes
Simopoulou et al. (2007) [46]	SF/Serum	17 OA, 5H	Significantly much higher in OA patients	Yes
Ku et al. (2009) [49]	SF	42 OA, 10H	Significantly higher in OA patients	Yes
Min et al. (2020) [45]	Serum	148 OA, 101H	Significantly higher in OA patients	Yes
Lübekke et al. (2013) [48]	SF from hip and knee	219	High leptin levels in SF were correlated with joint pain	Yes
Xiong et al. (2018) [57]	SF	13 OA, 7H	Significantly higher in OA patients than all the other groups	Yes
Kroon et al. (2019) [58]	Serum from hand and knee	6408	Leptin levels were positively associated with OA	Yes
Massengale et al. (2012) [55]	Serum from hand	2477	No significant difference between symptomatic, asymptomatic, and no hand OA	No
Yusuf et al. (2011) [54]	Serum from hand	248	Not associated with hand OA progression	No
De Boer et al. (2012) [14]	Serum from knee	172 OA, 132H	Significant difference between OA patients and control	Yes
Morales Abaunza et al. (2020) [56]	Serum from hand	44 OA, 30H	Significantly higher in patients with hand OA	Yes
Bas et al. (2014) [47]	Serum and SF from hip and knee	112 hip OA, 92 knee OA	Higher in knee OA than in hip OA joints	Yes

SF, synovial fluid; OA, osteoarthritis; H, healthy controls.