Differences between mean values (M  SEM) of Br, Cu, Fe, Rb, Sr, and Zn mass fraction (mg/kg, dry mass basis) in normal female thyroid of two Age Groups (AG).

Table 4: Differences between mean values (M  SEM) of Br, Cu, Fe, Rb, Sr, and Zn mass fraction (mg/kg, dry mass basis) in normal female thyroid of two Age Groups (AG).

Element	Female thyroid tissue				Ratio
	AG1 3.5-40 years n = 11	AG2 41-87 years n = 22	t-test p ≤	U-test p	AG2 to AG1
Br	13.1 ± 2.5	24.7 ± 3.5	0.0112	≤ 0.01	1.89
Cu	4.01 ± 0.60	4.45 ± 0.61	0.616	> 0.05	1.11
Fe	172 ± 26	263 ± 27	0.0240	≤ 0.01	1.53
Rb	5.30 ± 0.55	7.62 ± 0.64	0.0112	≤ 0.01	1.44
Sr	5.29 ± 1.12	3.63 ± 0.86	0.262	> 0.05	0.69
Zn	65.6 ± 12.7	106.2 ± 9.3	0.0176	≤ 0.01	1.62

M: Arithmetic mean; SEM: Standard Error of Mean; t-test: Student’s t-test; U-test: Wilcoxon-Mann-Whitney U-test; Statistically significant values are in bold.