3,3'-DIIODOTHYRONINE CONCENTRATIONS IN THE SERA OF PATIENTS WITH NONTHYROIDAL ILLNESSES AND BRAIN-TUMORS AND OF HEALTHY-SUBJECTS DURING ACUTE STRESS

In this article we describe the development of a highly sensitive, acc urate, and reproducible RIA for the measurement of 3,3'-diiodothyronin e (3,3'-T-2) in human serum and brain tissue. The detection limits wer e 1.8 fmol/g and 1.5 pmol/L in human brain tissue and serum, respectiv ely. Serum concentrations of 3,3'-T-2 were measured in 4 groups of pat ients with nonthyroidal illnesses (NTI), i.e. brain injuries (n = 15), sepsis (n = 24), Liver disease (n = 22), and brain tumors (n = 23). T he mean serum concentration of 3,3'-T-2 in 62 healthy controls was 46. 6 +/- 20.0 pmol/L. 3,3'-T-2 levels declined significantly with increas ing age. They were significantly lower in patients with brain injury ( 34.2 +/- 19.4 pmol/L; P = 0.006), were at the upper limit of normal in patients with sepsis (57.0 +/- 36.9 pmol/L; P = 0.06), and were eleva ted in patients with liver disease (72.6 +/- 56.7 pmol/L; P = 0.04) an d brain tumors (89.0 +/- 40.9 pmol/L; P = 0.01). The serum levels of T -3 were significantly lower than those in controls in all 4 patient gr oups. Serum concentrations of 3,3'-T-2 were significantly enhanced in 9 patients with hyperthyroidism (85.4 +/- 43.0 pmol/L; P = 0.01) and w ere reduced in 12 patients with hypothyroidism (14.9 +/- 9.2 pmol/L; P = 0.001). In both normal brain tissue, obtained either intraoperative ly or excised postmortem, and brain tumors, the concentrations of 3,3' -T-2 ranged between 50-300 fmol/g. In healthy controls, 2 different fo rms of acute stress (sleep deprivation and delivering a lecture) signi ficantly increased serum levels of T-4 and T-3, but did not affect tho se of 3,3'-T-2 or 3,5-T-2. In conclusion, our results show that, contr ary to expectation, a low T-3 syndrome in NTI is not always associated with low serum concentrations of 3,3'-T-2. The production of 3,3'-T-2 in NTT seems to be regulated in a disease-specific manner, resulting in unchanged, reduced, or elevated hormone concentrations.