Samec Barbara, Setnikar Gaja, Gaberscek Simona, Kocjan Tomaz
Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
Department of Nuclear Medicine, University Medical Centre Ljubljana, Ljubljana, Slovenia.
Exp Clin Endocrinol Diabetes. 2022 Apr;130(4):223-228. doi: 10.1055/a-1543-8826. Epub 2021 Jul 30.
Contrary to patients with hypothyroidism after radioiodine (HRI) or after thyroidectomy (HTh), patients with central hypothyroidism (CH) cannot rely on thyrotropin (TSH) level to guide their treatment with L-thyroxine (L-T4). Consequently, they are at constant risk of under- or overtreatment. We aimed to establish the adequacy of L-T4 treatment in patients with CH in our cohort.
Consecutive patients with CH on L-T4 treatment were compared with patients adequately treated for HRI or HTh. Levels of free thyroxine (fT) and free triiodothyronine (fT) were evaluated and the fT/fT ratio was calculated.
Forty patients with CH, 136 patients with HRI and 43 patients with HTh were included in this study. Patients with HRI were significantly younger than patients with HTh and CH (p<0.001 for both). Levels of fT were significantly lower in CH than in adequately treated patients with HRI and HTh (median (range), 15.6 (12.7-21.3), 18.4 (12.2-28.8), and 18.7 (13.8-25.5) pmol/L, respectively, p<0.001 for both comparisons). Levels of fT did not differ significantly (p=0.521) between CH, HRI and HTh (median (range), 4.5 (2.7-5.9), 4.3 (3.2-6.2), and 4.4 (2.9-5.5) pmol/L, respectively). Accordingly, the fT/fT ratio was significantly lower in the CH group than in HRI and HTh groups (median (range), 3.7 (2.5-5.2), 4.2 (1.2-7.7), and 4.4 (2.5-6.1), respectively, p<0.001 for both comparisons).
Patients with CH have lower fT levels and lower fT/fT ratios than patients adequately treated for HRI or HTh. The cause for this difference may be the unreliable TSH levels in patients with CH.
