title: Hypothyroidism after hemithyroidectomy.
abstract: BACKGROUND
  The risk of hypothyroidism after hemithyroidectomy is variable, and most estimates come from single institutional studies. The purpose of the present study was to determine the incidence of hypothyroidism at the population level, and to evaluate predictive factors for hypothyroidism after hemithyroidectomy.
  
  
  METHODS
  This retrospective study identified euthyroid patients who underwent hemithyroidectomy between 2000 and 2010 for benign disease in Kaiser Permanente Southern California regional hospitals. The incidence of hypothyroidism [thyroid stimulating hormone (TSH) levels >4 μIU/ml] was analyzed. The independent effect of age-quartile, gender, race, thyroiditis, and preoperative TSH level on the development of hypothyroidism was evaluated.
  
  
  RESULTS
  Of 1,240 euthyroid patients identified, 417 (34 %) developed hypothyroidism, and 314 (25 % of total group) needed levothyroxine. Hypothyroidism was more common in age-quartile 2 (32 %), age-quartile 3 (37 %), and age-quartile 4 (42 %) than in age-quartile 1 (25 %) [adjusted odds ratio (OR) = 1.87; 95 % confidence interval (CI) 1.27-2.76, p = 0.002; age-quartile 4 compared to age-quartile 1]. Hypothyroidism was more frequent with increasing preoperative TSH levels 36, 72, and 92 % in patients with TSH levels of 1.0-2, 2.01-3, and 3.01-4 μIU/ml, respectively, compared to 17 % in those with TSH levels <1 μIU/ml [adjusted OR = 45.1; 95 % CI 13.5-151, p < 0.0001; 3.01-4 μIU/ml compared to <1 μIU/ml]. Thyroiditis was also an independent predictor of hypothyroidism.
  
  
  CONCLUSIONS
  About one third of euthyroid patients who undergo hemithyroidectomy develop hypothyroidism. The most significant predictor is the preoperative TSH level, with an approximate doubling of risk for each 1 unit of TSH increase over 1 μIU/ml. Our categorical scale is simple and allows for easy recall when counseling patients preoperatively.
authors: Department of Surgery, Mount Sinai Hospital, One Gustave L. Levy Place, New York, NY, 10029, USA, meena.said@mountsinai.org.
authors: Meena
authors: M
authors: Said
authors: Vicki
authors: V
authors: Chiu
authors: Philip I
authors: PI
authors: Haigh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000453:epidemiology / Q000209:etiology*; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D017063:Outcome Assessment, Health Care; D011183:Postoperative Complications / Q000453:epidemiology / Q000209:etiology*; D012189:Retrospective Studies; D012307:Risk Factors; D013965:Thyroidectomy / Q000379:methods; D055815:Young Adult
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