Table 1. Characteristics of the study population.
| Controlled | Overtreated | Undertreated | p*1 | p*2 | |
| Participants, N (%) | 518 (78.2) | 117 (17.7) | 27 (4.1) | < 0.001 | < 0.001 |
| Age (years), M (SD) | 58.2 (13.9) | 58.8 (13.6) | 59.4 (15.5) | 0.675 | 0.721 |
| Sex (women), N (%) | 435 (84.0) | 96 (82.1) | 21 (77.8) | 0.659 | 0.432 |
| Education, N (%) | |||||
| Low | 16 (3.1) | 2 (1.8) | 0 (0.0) | 0.474 | – |
| Middle | 276 (54.1) | 57 (50.4) | 17 (63.0) | Ref. | Ref. |
| High | 218 (42.7) | 54 (47.8) | 10 (37.0) | 0.369 | 0.457 |
| Smoking, N (%) | |||||
| Never | 216 (44.5) | 50 (45.0) | 11 (42.3) | Ref. | Ref. |
| Former | 219 (45.2) | 42 (37.8) | 10 (38.5) | 0.371 | 0.775 |
| Current | 50 (10.3) | 19 (17.1) | 5 (19.2) | 0.116 | 0.261 |
| BMI (kg/m2) | 26.5 (4.9) | 25.7 (4.7) | 25.9 (4.7) | 0.064 | 0.439 |
| TSH (mU/L), M (SD) | 1.6 (0.8) | 0.3 (0.2) | 7.3 (3.4) | 0.074 | 0.311 |
| Diabetes, N (%) | 29 (5.7) | 7 (6.0) | 2 (7.4) | 0.961 | 0.787 |
| Hypertension, N (%) | 238 (47.1) | 49 (42.2) | 14 (51.9) | 0.196 | 0.807 |
| CVD, N (%) | 54 (10.5) | 10 (8.6) | 5 (18.5) | 0.425 | 0.274 |
| CKD, N (%) | 26 (5.4) | 9 (8.0) | 4 (14.8) | 0.414 | 0.089 |
| LT4 intake duration, N (%) | |||||
| ≤ 12 months | 29 (5.6) | 8 (6.9) | 3 (11.1) | Ref. | Ref. |
| 13–36 months | 80 (15.4) | 16 (13.8) | 2 (7.4) | 0.481 | 0.277 |
| > 36 months | 409 (79.0) | 92 (79.3) | 22 (81.5) | 0.584 | 0.277 |
| Iodine supplementation, N (%) | 145 (28.5) | 31 (26.5) | 3 (11.1) | 0.610 | 0.052 |
| Polypharmacy, N (%) | 161 (31.1) | 38 (32.5) | 9 (33.3) | 0.907 | 0.956 |
| Global cognition (z-score), M (SD) | −0.1 (0.6) | −0.1 (0.7) | −0.1 (0.8) | 0.732 | 0.641 |
Treatment status “controlled” (TSH 0.56–4.27 mU/L), “overtreated” (TSH < 0.56 mU/L), “undertreated” (TSH > 4.27 mU/L). Group differences were calculated with logistic regression adjusted for age and sex (age and sex were only adjusted for the other respectively).
*1 Adjusted for age and sex (overtreated compared with controlled)
*2 Adjusted for age and sex (undertreated compared with controlled)
BMI, Body mass index; CKD, chronic kidney disease; CVD, cardiovascular disease; LT4, levothyroxine; M, mean; N, number of participants; Ref, reference group; SD, standard deviation; TSH: thyrotropin.