title: Hypothyroidism and hyponatremia: data from a series of patients with iatrogenic acute hypothyroidism undergoing radioactive iodine therapy after total thyroidectomy for thyroid cancer.
abstract: OBJECTIVE
  The aim of the present study was to evaluate the role of hypothyroidism as a cause of hyponatremia in a clinical model of iatrogenic acute hypothyroidism due to thyroid hormone withdrawal prior to ablative radioactive iodine (RAI) therapy after total thyroidectomy.
  
  
  METHODS
  The study group consisted of 101 differentiated thyroid cancer (DTC) patients (77 women and 24 men). Plasma concentration of thyroid-stimulating hormone ([TSH]) and sodium ([Na+]) was evaluated before total thyroidectomy (pre[TSH] and pre[Na+]) and on the day of RAI therapy (post[TSH] and post[Na+]).
  
  
  RESULTS
  The frequency of hypothyroidism-associated hyponatremia was 4 % (4/101). Pre[Na+] was significantly higher than post[Na+] (140.7 ± 1.6 vs 138.7 ± 2.3 mEq/L, p = 0.012). Moreover, a linear correlation was identified between pre[Na+] and post[Na+].
  
  
  CONCLUSIONS
  Iatrogenic acute hypothyroidism-related hyponatremia is uncommon. However, because of the significant reduction of [Na+] in the transition from euthyroidism to iatrogenic hypothyroidism, the value of pre[Na+] should be viewed as a parameter to be considered. Since it acts as an independent risk factor for the development of hyponatremia, patients with a pre[Na+] close to the lower limit of normal range may deserve a closer monitoring of [Na+].
authors: Endocrine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy.
authors: L
authors: L
authors: Vannucci
authors: Endocrine Unit, Careggi Hospital, Largo Brambilla 3, 50134, Florence, Italy.
authors: G
authors: G
authors: Parenti
authors: Radiotherapy Unit, Careggi Hospital, Largo Brambilla 3, 50134, Florence, Italy.
authors: G
authors: G
authors: Simontacchi
authors: Andrologyy and Sexual Medicine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy.
authors: G
authors: G
authors: Rastrelli
authors: Endocrine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy.
authors: C
authors: C
authors: Giuliani
authors: Central Laboratory, Azienda Ospedaliero Universitaria Careggi, Largo Brambilla 3, 50139, Florence, Italy.
authors: A
authors: A
authors: Ognibene
authors: Endocrine Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale Pieraccini, 6, 50139, Florence, Italy. alessandro.peri@unifi.it.
authors: A
authors: A
authors: Peri
mesh_terms: D000208:Acute Disease; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000209:etiology / Q000532:radiotherapy*; D007037:Hypothyroidism / Q000209:etiology / Q000532:radiotherapy*; D007049:Iatrogenic Disease; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000532:radiotherapy*; D011379:Prognosis; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000150:complications / Q000601:surgery*; D013965:Thyroidectomy / Q000009:adverse effects*
chemical_list: D007457:Iodine Radioisotopes
keywords: Hyponatremia; Hypothyroidism; RAI therapy; Thyroid cancer