Health status, mood, and cognition in experimentally induced subclinical thyrotoxicosis.
OBJECTIVE
Our objective was to determine whether subclinical thyrotoxicosis alters health status, mood, and/or cognitive function.


METHODS
This was a double-blinded, randomized, cross-over study of usual dose l-T(4) (euthyroid arm) vs. higher dose l-T(4) (subclinical thyrotoxicosis arm) in hypothyroid subjects.


METHODS
A total of 33 hypothyroid subjects receiving l-T(4) were included in the study.


METHODS
Subjects underwent measurements of health status, mood, and cognition: Short Form 36 (SF-36); Profile of Mood States (POMS); and tests of declarative memory (Paragraph Recall, Complex Figure), working memory (N-Back, Subject Ordered Pointing, and Digit Span Backwards), and motor learning (Pursuit Rotor). These were repeated after 12 wk on each of the study arms.


RESULTS
Mean TSH levels decreased from 2.15 to 0.17 mU/liter on the subclinical thyrotoxicosis arm (P < 0.0001), with normal mean free T(4) and free T(3) levels. The SF-36 physical component summary and general health subscale were slightly worse during the subclinical thyrotoxicosis arm, whereas the mental health subscale was marginally improved. The POMS confusion, depression, and tension subscales were improved during the subclinical thyrotoxicosis arm. Motor learning was better during the subclinical thyrotoxicosis arm, whereas declarative and working memory measures did not change. This improvement was related to changes in the SF-36 physical component summary and POMS tension subscales and free T(3) levels.


CONCLUSIONS
We found slightly impaired physical health status but improvements in measures of mental health and mood in l-T(4) treated hypothyroid subjects when subclinical thyrotoxicosis was induced in a blinded, randomized fashion. Motor learning was also improved. These findings suggest that thyroid hormone directly affects brain areas responsible for affect and motor function.
Samuels
M H
MH
Division of Endocrinology, Diabetes and Clinical Nutrition, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA. samuelsm@ohsu.edu
Schuff
K G
KG
Carlson
N E
NE
Carello
P
P
Janowsky
J S
JS
D000328:Adult; D000339:Affect; D003071:Cognition; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008568:Memory; D008875:Middle Aged; D013960:Thyroid Function Tests; D013971:Thyrotoxicosis / Q000523:psychology*