title: Biochemical Effects of Levothyroxine Withdrawal in Patients with Differentiated Thyroid Cancer.
abstract: BACKGROUND
  Patients with differentiated thyroid carcinoma (DTC) are submitted to withdrawal of levothyroxine (LT4) aftter thyroidectomy, in order to undergo radiodine ((131)I) treatment.
  
  
  METHODS
  A total of 345 patients with a history of DTC were enrolled in the study. Their biochemical profile and serum free triiodothyronine (FT3), free thyroxine (FT4) and thyrotropin (TSH) levels were measured during withdrawal of LT4 treatment, and several months after restarting LT4.
  
  
  RESULTS
  During withdrawal, the intra-individual percentage increase in total cholesterol, low density lipoprotein-cholesterol, very low density lipoprotein-cholesterol and triglycerides was of the order of 60-80% and that for high density lipoprotein-cholesterol 30%. Creatinine increased by 30%, whereas Na and K levels decreased by 1%. The increase for creatine phosphate kinase was around 200-300%, for aspartate aminotransferase and alanine aminotransferase 50-80%, for γ-glutamyl transpeptidase 10-20%, and for lactate dehydrogenase 25%. Glucose decreased by 1-4%.
  
  
  CONCLUSIONS
  Short-term, acute hypothyroidism in patients with DTC induces significant alterations in several biochemical parameters. The presence of other deteriorating diseases should be considered before submitting these patients to LT4 withdrawal.
authors.affiliation: Department of Endocrinology, Metaxa Anticancer Hospital, Piraeus, Athens, Greece george.papadakis.md@gmail.com.
authors.forename: Georgios
authors.initials: G
authors.lastname: Papadakis
authors.affiliation: Department of Endocrinology, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Styliani
authors.initials: S
authors.lastname: Kalaitzidou
authors.affiliation: Department of Endocrinology, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Eleni
authors.initials: E
authors.lastname: Triantafillou
authors.affiliation: Department of Endocrinology, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Aspasia
authors.initials: A
authors.lastname: Drosou
authors.affiliation: Department of Otolaryngology, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Kassiani
authors.initials: K
authors.lastname: Kakava
authors.affiliation: Department of Biochemistry, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Dogkas
authors.affiliation: Department of Endocrinology, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Theodora
authors.initials: T
authors.lastname: Pappa
authors.affiliation: Department of Endocrinology, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Victoria
authors.initials: V
authors.lastname: Kaltzidou
authors.affiliation: Department of Endocrinology, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Athanasia
authors.initials: A
authors.lastname: Tertipi
authors.affiliation: Department of Biochemistry, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Villiotou
authors.affiliation: Department of Endocrinology, Metaxa Anticancer Hospital, Piraeus, Athens, Greece.
authors.forename: Anastasios
authors.initials: A
authors.lastname: Pappas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy* / Q000209:etiology; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D013375:Substance Withdrawal Syndrome / Q000097:blood; D013964:Thyroid Neoplasms / Q000097:blood* / Q000150:complications / Q000532:radiotherapy; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage* / Q000097:blood; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine
keywords: Differentiated thyroid carcinoma; biochemical alterations; hypothyroidism; thyroxine withdrawal