Table I.

Control Groups and Exposed Groups Summary Statistics

	Control groups						Exposed groups
	n	n					n	n
Variable	Studies	Groups	Mean	STD	Min	Max	Studies	Groups	Mean	STD	Min	Max
Age (years)	7	7	37.64	6.09	28.80	43.90	15	17	39.43	8.81	30.50	69.00
Duration of exposure (years)	0	0					14	16	9.79	5.67	4.20	24.00
Blood lead (µg/dL)	8	8	8.30	7.60	2.10	20.90	16	18	43.27	18.06	14.28	73.53
Thyroid stimulating hormone (µU/mL)	7	7	1.40	0.78	0.50	3.02	14	16	1.89	0.89	0.51	4.10
Total thyroxine (µg/dL)	6	6	7.30	1.76	5.91	10.70	14	15	7.21	1.36	4.68	9.40
Free thyroxine (ng/dL)	6	6	1.10	1.01	0.09	2.86	11	12	1.33	0.67	0.09	2.86
Total triiodothyronine (ng/dL)	5	5	139.13	18.40	125.50	171.00	11	12	127.03	20.41	94.00	175.00
Free triiodothyonine (pg/dL)	3	3	266.92	103.25	163.64	370.13	4	5	337.88	98.87	187.01	430.00

STD: standard deviation

Min: minimum

Max: maximum