Table 13.

Studies examining enzymes of the γ-glutamyl cycle or transulphuration pathway in autism

Source	Study	Study size (Male:Female)	Cases1	Controls1	P values	Overall finding	Units of measure
Glutathione peroxidase
Plasma	Yorbik et al. 2002 [71]	45 cases, (39 M, 6 F) 41 controls, (35 M, 6 F)	270 ± 40	390 ± 80	< 0.05	low	U/L
	Söğüt et al. 2003 [72]	27 cases, (16 M, 11 F) 30 controls, (16 M, 14 F)	40.9 ± 11.3	24.2 ± 6.3	< 0.0001	high	U/L
	Al-Gadani et al. 2009 [81]	30 cases, (22 M, 8 F) 30 controls, (20 M, 10 F)	2468.8 ± 999.3	1438.5 ± 611.2	< 0.05	high	U/L
	Mostafa et al. 2010 [83]	44 cases, (30 M,14 F) 44 controls, (30 M, 14 F)	441.5 (100)2	589 (176)2	< 0.001	low	U/L
Erythrocytes	Golse et al. 1978 [63]	24 cases, (17 M, 7 F) 6 controls, (2 M, 4 F)	4.7 ± 0.29	8.45 ± 0.95	< 0.0001	low	U/g haemoglobin
	Yorbik et al. 2002 [71]	45 cases, (39 M, 6 F) 41 controls, (35 M, 6 F)	28.72 ± 2.64	38.01 ± 5.03	< 0.05	low	U/g haemoglobin
	Pasca et al. 2006 [74]	12 cases, (9 M, 3 F) 9 controls, (6 M, 3 F)	7.75 ± 0.93	7.45 ± 0.65	ns	ns	U/g haemoglobin
	Vergani et al. 2011 [84]	28 cases (21 M, 7 F) 32 controls (20 M, 12 F)			ns	ns	nmols NADPH/min/mg haemoglobin
Platelets	Golse et al. 1978 [63]	36 cases, (15 M, 21 F) 21 controls, (9 M, 12 F)	51.53 ± 1.61	46.56 ± 2.69	ns	ns	U/g platelet protein
Glutathione reductase
Plasma	Al-Yafee et al. 2011 [85]	20 cases (20 M, 0 F) 20 controls (20 M, 0 F)	70.25 ± 16.35	60.19 ± 15.42	0.052	trend high	U/L
Glutathione-s-transferase
Plasma	Al-Yafee et al. 2011 [85]	20 cases (20 M, 0 F) 20 controls (20 M, 0 F)	0.42 ± 0.18	0.73 ± 0.37	0.002	low	μmol/min/ml

ns Not significant ¹Mean ± standard deviation ² Median and interquartile range