title: Comparison of conventional L-thyroxine withdrawal and moderate hypothyroidism in preparation for whole-body 131-I scan and thyroglobulin testing.
abstract: OBJECTIVE
  After thyroidectomy for thyroid cancer, patients often withdraw L-T4 for diagnostic or therapeutic purposes, showing signs and symptoms of hypothyroidism. A slighter hypothyroidism (reducing L-T4 to one-half) has been proposed to limit these inconveniences. We evaluated half-dose L-T4 protocol, in comparison to conventional L-T4 withdrawal, in terms of effectiveness and improvement of clinical and biochemical disorders.
  
  
  METHODS
  We randomized 55 thyroid cancer patients into two groups: 29 patients underwent 5 weeks of half-dose of previous L-T4 treatment (HD group); 26 patients replaced L-T4 with L-T3 for 3 weeks followed by 2 weeks of withdrawal (TW group). Clinical features (Zulewsky clinical score) and biochemical parameters (lipids, liver, and muscle enzymes) were evaluated in all patients at baseline and after 5 weeks.
  
  
  RESULTS
  Total cholesterol, creatine kinase, lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase increased at 5 weeks in both groups, but significantly more in TW, but no difference was found by clinical score. Patients who achieved the thyroid-stimulating hormone (TSH) target value (25 µU/ml) were 92.3% in TW group and 48.3% in HD group (p < 0.001). In the HD group, only basal TSH statistically correlated with the achievement of the TSH target. Receiver operating characteristic curves indicated that a basal TSH ≥0.52 μU/ml is required to reach an adequate TSH level.
  
  
  CONCLUSIONS
  Half-dose L-T4 protocol, compared to conventional L-T4 withdrawal, is associated with less biochemical disorders but no significant clinical advantage. Therefore, the half-dose protocol reaches an adequate TSH target in 48.3% of patients and is not effective unless basal serum TSH is ≥0.52 μU/ml.
authors.affiliation: Endocrinology, Department of Sperimental Clinical Medicine, Garibaldi-Nesima Medical Center, University of Catania, Via Palermo 636, 95122, Catania, Italy, ileniamarturano@yahoo.it.
authors.forename: I
authors.initials: I
authors.lastname: Marturano
authors.forename: M
authors.initials: M
authors.lastname: Russo
authors.forename: A
authors.initials: A
authors.lastname: Spadaro
authors.forename: A
authors.initials: A
authors.lastname: Latina
authors.forename: P
authors.initials: P
authors.lastname: Malandrino
authors.forename: C
authors.initials: C
authors.lastname: Regalbuto
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000139:chemically induced / Q000000981:diagnostic imaging; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D013954:Thyroglobulin / Q000097:blood; D013964:Thyroid Neoplasms / Q000097:blood / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000009:adverse effects* / Q000097:blood / Q000627:therapeutic use; D014284:Triiodothyronine / Q000097:blood
chemical_list: D007457:Iodine Radioisotopes; D014284:Triiodothyronine; D013972:Thyrotropin; D013954:Thyroglobulin; D013974:Thyroxine