Table 1.- Variants (SNPs) included in the PRS calculation
(Disease/Trait: Thyroid_volume)
rsID	Risk allele	Effect size
rs10917468	C	0.419
rs4338740	C	0.372
rs12045440	T	0.322
rs3813579	A	0.278
Effect size: LN(OR)

Table 2.- PRS Score distribution among populations and regions
(Disease/Trait: Thyroid_volume)
	count	mean	sd	se	lower.ci	upper.ci
Pyrenean regions
WEST	168	0.127	0.056	0.004	0.119	0.136
SOUTH	83	0.133	0.056	0.006	0.121	0.145
EAST	146	0.135	0.058	0.005	0.126	0.145
Populations
IBS	107	0.139	0.058	0.006	0.128	0.150
PIR	397	0.131	0.057	0.003	0.126	0.137

Table 3.- Pairwise t-test for PRS score among populations and regions
(Disease/Trait: Thyroid_volume)
group1	group2	n1	n2	p	p.signif	p.adj	p.adj.signif
IBS	PIR	107	397	0.2070	ns	1.000	ns
IBS	WEST	107	168	0.0878	ns	0.878	ns
IBS	SOUTH	107	83	0.4640	ns	1.000	ns
IBS	EAST	107	146	0.5810	ns	1.000	ns
WEST	SOUTH	168	83	0.4370	ns	1.000	ns
WEST	EAST	168	146	0.2130	ns	1.000	ns
SOUTH	EAST	83	146	0.7890	ns	1.000	ns
* p < .05, ** p < .01, *** p < .001

Table 4.- Chi-square test comparison of percentile counts on Pyrenean regions compared to Iberian peninsula population
(Disease/Trait: Thyroid_volume)
Percentile rank	PIR				WEST				SOUTH				EAST
	adj.std.val	p.value	sig.val		adj.std.val	p.value	sig.val		adj.std.val	p.value	sig.val		adj.std.val	p.value	sig.val
pct95	−0.900	0.368	.	white	−1.410	0.159	.	white	−0.900	0.368	.	white	−0.350	0.726	.	white
pct75.95	0.100	0.920	.	white	0.070	0.944	.	white	0.100	0.920	.	white	0.370	0.711	.	white
pct50.75	−1.340	0.180	.	white	−0.730	0.465	.	white	−1.340	0.180	.	white	−1.020	0.308	.	white
pct25.50	1.080	0.280	.	white	0.020	0.984	.	white	1.080	0.280	.	white	0.310	0.757	.	white
pct25	0.620	0.535	.	white	1.310	0.190	.	white	0.620	0.535	.	white	0.590	0.555	.	white
adj.std.val: Adjusted standardized residuals value; p.value: P value; sig.val: statistical significance, * p < .05, ** p < .01, *** p < .001; red dash to bottom: lower counts than reference; green dash to up: upper counts than reference