eTable 3. Results of the online survey (n=456).
| LT4 users | Missing | LT4 treatment status | |||
| Controlled | Overtreated | Undertreated | |||
| Participants, N | 456 | 361 | 82 | 13 | |
| Sex, N (%) | 0.0% | ||||
| Women | 379 (83.1) | 300 (83.1) | 66 (80.5) | 13 (100.0) | |
| Men | 76 (16.7) | 60 (16.6) | 16 (19.5) | 0 (0.0) | |
| Diverse | 1 (0.2) | 1 (0.3) | 0 (0.0) | 0 (0.0) | |
| LT4 intake (years), M (SD) | 21.3 (12.2) | 9.2% | 20.6 (12.0) | 24.1 (12.9) | 22.8 (9.9) |
| Diagnosis-based initiation of LT4, N (%) | 450 | 1.2% | |||
| Hypothyroidism | 174 (38.7) | 139 (39.1) | 30 (36.6) | 5 (38.5) | |
| Benign struma | 82 (18.2) | 59 (16.6) | 22 (26.8) | 1 (7.7) | |
| Hashimoto | 122 (27.1) | 94 (26.5) | 23 (28.0) | 5 (38.5) | |
| Other diagnosis | 51 (11.3) | 44 (12.4) | 5 (6.1) | 2 (15.4) | |
| Unknown | 21 (4.7) | 19 (5.4) | 2 (2.4) | 0 (0.0) | |
| TSH monitoring frequency, N (%) | 19.3% | ||||
| Every 6 months | 61 (16.6) | 43 (14.6) | 13 (21.0) | 5 (45.5) | |
| Yearly | 161 (43.8) | 131 (44.4) | 25 (40.3) | 5 (45.5) | |
| Every 1–2 years | 77 (20.9) | 63 (21.4) | 14 (22.6) | 0 (0.0) | |
| Irregularly | 56 (15.2) | 48 (16.3) | 7 (11.3) | 1 (9.1) | |
| No monitoring | 13 (3.5) | 10 (3.4) | 3 (4.8) | 0 (0.0) | |
| Most recent LT4 dose adjustment in years, M (SD) | 6.2 (6.0) | 24.1% | 6.5 (6.1) | 5.6 (6.1) | 3.1 (1.7) |
| Thyroid examinations performed | 9.0% | ||||
| Biopsy | 54 (11.8) | 42 (11.6) | 11 (13.4) | 1 (7.7) | |
| Ultrasound | 389 (85.3) | 305 (84.5) | 72 (87.8) | 12 (92.3) | |
| Scintigraphy | 275 (60.3) | 218 (60.4) | 50 (61.0) | 7 (53.8) | |
Treatment status controlled: TSH 0.56–4.27 mU/L; overtreated: TSH < 0.56 mU/L; undertreated: TSH > 4.27 mU/L
LT4, Levothyroxine; M, mean; N, number of participants; SD, standard deviation; TSH, thyrotropin