title: Neuropsychological function and symptoms in subjects with subclinical hypothyroidism and the effect of thyroxine treatment.
abstract: OBJECTIVE
  Our objective was to examine the relation between neuropsychological function and subclinical hypothyroidism (SHT), defined as serum TSH of 3.5-10.0 mIU/liter and normal serum free T4 and free T3 levels, and to study the effect of T4 supplementation.
  
  
  METHODS
  A total of 89 subjects (45 males) with SHT and 154 control subjects (72 males) were recruited from a general health survey (the fifth Tromsø study). Sixty-nine of those with SHT were included in a placebo-controlled, double-blind intervention study with T4 medication for 1 yr.
  
  
  METHODS
  We used fourteen tests of cognitive function, Beck Depression Inventory, General Health Questionnaire, and a questionnaire on hypothyroid symptoms.
  
  
  RESULTS
  The mean +/- sd serum TSH in the SHT and control group were 5.57 +/- 1.68 and 1.79 +/- 0.69 mIU/liter, respectively. There were no significant differences in cognitive function and hypothyroid symptoms between the two groups, but those with SHT scored significantly better than the controls on the GHQ-30. At the end of the intervention study, serum TSH in the T4 group (n = 36) and the placebo group (n = 33) were 1.52 +/- 1.51 and 5.42 +/- 1.96 mIU/liter, respectively. T4 substitution had no effect on any of the parameters measured.
  
  
  CONCLUSIONS
  In subjects with SHT where the serum TSH level is in the 3.5-10.0 mIU/liter range, there is no neuropsychological dysfunction, and compared with healthy controls, there is no difference in symptoms related to hypothyroidism.
authors.affiliation: Institute of Clinical Medicine (R.J., K.W.), University of Tromsø, 9037 Tromsø, Norway. rolf.jorde@unn.no
authors.forename: Rolf
authors.initials: R
authors.lastname: Jorde
authors.forename: Knut
authors.initials: K
authors.lastname: Waterloo
authors.forename: Hilde
authors.initials: H
authors.lastname: Storhaug
authors.forename: Audhild
authors.initials: A
authors.lastname: Nyrnes
authors.forename: Johan
authors.initials: J
authors.lastname: Sundsfjord
authors.forename: Trond Geir
authors.initials: TG
authors.lastname: Jenssen
mesh_terms: D000328:Adult; D000368:Aged; D003071:Cognition / Q000502:physiology; D015331:Cohort Studies; D004644:Emotions / Q000502:physiology; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy* / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D009664:Norway; D012044:Regression Analysis; D011795:Surveys and Questionnaires; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000627:therapeutic use*
chemical_list: D013972:Thyrotropin; D013974:Thyroxine