Table 1. Demographic and characteristics of studies included in the meta-analysis.

Reference (first author)	Country	Parients No		Age		Gender (male%)		Newcastle-Ottawa score
		PTX	CTRL	PTX	CTRL	PTX	CTRL	Selection	Comparability	Exposure
Ivarsson etal. 2015 [23]	Sweden	423	1234	55.2	56	48.2	50.1	***	**	**
Komaba et al. 2015 [17]	Japan	4428	4428	59.1 ± 11.6	59.3±12.3	55.8	55.7	***	**	***
Conzo et al. 2013 [20]	Italy	30	20	51.5±10.89	55±11.2	26.7	40	***	*	*
Sharma et al. 2013 [51]	US	150	1044	42.1	42.2	46.7	46.7	***	**	**
Goldstein et al 2013 [21]	Brazil	123	128	46	50	46.3	44.5	***	*	**
Iwamoto et al 2012 [16]	Japan	88	88	60.6±8.4	60.5±8.4	53.4	53.4	***	**	**
Kestenbaun et al. 2004 [24]	US	4558	4558	47.6	47.6	42.5	42.5	***	**	*
Trombetti et al. 2007 [44]	Switzerland	40	80	42.6	55	45	51	***	**	**
Ho LC et al. 2016 [45]	Taiwan	998	998	54.7	55	42.9	42.5	***	**	***
Moldovan et al. 2015 [22]	Romania	26	26	51.62±9.92	49.65±11.49	53.84	23.07	***	*	**
Li-Wedong et al 2016 [46]	China	53	92	63.1±13.8	53.8±15	56.6	70.6	***	*	*
Costa-Hong et al 2007 [18]	Brazil	50	68	52	59	43±10	45±12	**	**	*
Dussol B et al 2007[47]	France	19	32	N/A	N/A	N/A	N/A	**	**	*
Ma T-L et al 2015[48]	Taiwan	60	161	N/A	N/A	N/A	N/A	**	**	*
Lin H-C 2014[19]	Taiwan	30	23	53.3 ± 13.3	53.4 ±13.9	43	61	***	**	*

Abbreviations: PTX-parathyroidectomy, CTRL- control

*- Stars awarded for each quality item (Newcastle-Ottawa scale). For each domain, either a "star" or "no star" is assigned, with a "star" indicating that study design element was considered adequate and less likely to introduce bias. For Selection (of the exposed cohort, of the non-exposed cohort, ascertainment of exposure and outcome of interest) a maximum of four stars may be assigned. A maximum of two stars can be given for Comparability and a maximum of 3 stars can be given for Exposure (assessment of outcome, length of follow-up and adequacy offollow-up). A study could receive a maximum of nine stars.