title: Serum thyrotrophin at baseline predicts the natural course of subclinical hyperthyroidism.
abstract: OBJECTIVE
  Optimal therapeutic strategies for subclinical hyperthyroidism are undecided. Overt disease develops in a minority of cases, but the risk factors for progression remain unclear. We examined whether a baseline thyrotrophin (TSH) predicted progression to overt hyperthyroidism in asymptomatic individuals with subclinical hyperthyroidism.
  
  
  METHODS
  This was a retrospective study of 323 patients with subclinical hyperthyroidism seen in our institution from 2003 to 2010 (mean age 71 years, males 26·9%, females 73·1%, mean follow-up duration 32 months, range 6-93 months). Serum TSH and free thyroxine (FT4) were documented at baseline and during follow-up. After excluding individuals with nonthyroid causes of low TSH, patients were grouped according to initial TSH as: TSH 0·10-0·39 mU/l (grade I) and TSH < 0·10 mU/l (grade II).
  
  
  RESULTS
  Only 38 patients (11·8%) developed overt hyperthyroidism with annual progression rates of 0·6-3·7%. Most patients reverted to normal thyroid status (31·6%) or remained subclinically hyperthyroid (56·7%). Progression to frank hyperthyroidism was higher in grade II than in grade I patients (20·3% vs 6·8%, P < 0·001, Chi square test). Kaplan-Meier curves showed faster progression rates in grade II than grade I (P < 0·001, log rank test). In stepwise multivariate Cox regression analysis, TSH < 0·1 mU/l was associated with overt hyperthyroidism (hazard ratio 3·4, confidence interval 1·6-7·0), whereas age, gender, FT4 and aetiological diagnosis were not associated with hyperthyroidism.
  
  
  CONCLUSIONS
  Thyrotrophin predicts overt hyperthyroidism in asymptomatic individuals with subclinical hyperthyroidism. Patients with TSH < 0·10 mU/l have a higher risk of progressing to hyperthyroidism than those with TSH 0·10-0·39 mU/l.
authors.affiliation: Department of Endocrinology and Diabetes, Prince Charles Hospital, Cwm Taf Local Health Board, Merthyr Tydfil, UK.
authors.forename: G
authors.initials: G
authors.lastname: Das
authors.forename: T A
authors.initials: TA
authors.lastname: Ojewuyi
authors.forename: P
authors.initials: P
authors.lastname: Baglioni
authors.forename: J
authors.initials: J
authors.lastname: Geen
authors.forename: L D
authors.initials: LD
authors.lastname: Premawardhana
authors.forename: O E
authors.initials: OE
authors.lastname: Okosieme
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058070:Asymptomatic Diseases; D001481:Basal Metabolism / Q000502:physiology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000175:diagnosis* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood*
chemical_list: D013972:Thyrotropin