Unreliability of the use of thyroglobulin concentration in postmortem blood samples in forensic diagnosis

Previous studies have reported that the concentration of thyroglobulin (Tg) in heart blood is high in cases of asphyxia by neck compression such as hanging, strangulation, and throttling and in those with traumatic injuries to the head. However, we have experienced cases in which we observed high Tg concentrations without such findings. Therefore, we analyzed the influence of postmortem changes on Tg concentration. Of 253 forensic autopsies conducted at our institution, we analyzed 44 cases without the findings presumed to increase Tg concentration. We collected right heart blood (RHB) and left heart blood (LHB) separately and measured Tg concentrations in each. The Tg concentration of the RHB in 19 (43%) cases and that of the LHB in 10 (23%) cases was higher than the standard value (200ng/ml) obtained in previous studies. In some cases, we found large differences between the Tg concentrations of RHB and LHB. We suggest that Tg concentration can increase above the standard value and that a difference between the Tg concentration of RHB and LHB arises as a result of postmortem changes. Consequently, if there is a large difference between the Tg concentration of RHB and LHB, the concentration of Tg should not be used as a basis for forensic diagnosis.