Postmortem measurements of thyroid hormones in blood and vitreous humor combined with histology

The aim of this study was to investigate whether clinical reference premort em values can be used to assess postmortem concentrations of thyroxine, tri iodothyronine, and thyroid stimulating hormone (TSH), to compare the postmo rtem concentrations in blood and vitreous humor, and to study the possibili ty of diagnosing hyperthyroidism by comparing thyroid histologic appearance and postmortem hormone values. Biochemical analyses of free thyroxine (FT4 ), free triiodothyronine (FT3), and TSH in femoral blood and vitreous humor were made in 38 cases. In 40 cases, the hormones and thyroid histologic ap pearance were studied; 22 had no significant pathologic changes, and 18 sho wed focal hyperplasia of the follicular epithelium. A positive correlation was seen between the femoral blood and vitreous humor concentrations of FT4 (R = 0.66) but not between the corresponding concentrations of FT3 and TSH . A positive correlation was also seen between FT3 and FT4 in femoral blood (R = 0.74). In cases with normal thyroid histologic appearance, 58% were f ound to have FT4 values >24 pmol/L (clinical reference interval 9-24 pmol/L ), mean value (27.5 +/- 9.4 pmol/L), which did not differ from the FT4 valu es in the cases with hyperplasia, 31.6 +/- 15 pmol/L. Only 5% of the T3 mea surements in the group with normal histologic appearance were >9 pmol/L (cl inical reference interval 3-9 pmol/L). The mean value of FT3 in cases with normal histologic appearance was 3.3 +/- 1.3 pmol/L, and in the group with hyperplasia 8.6 +/- 6.1 pmol/L. The difference was statistically significan t (P <.005). It is concluded that postmortem values of FT3 and FT4 in femor al blood are fairly comparable to premortem clinical reference values, but the upper normal limit, especially for T4, has to be adjusted upward. Analy sis of vitreous humor cannot be used post mortem to assess thyroid function . Histologically, hyperplastic changes correlate well with elevated FT3 in femoral blood.