Thyroxine therapy in euthyroid patients does not affect body composition or muscular function.
OBJECTIVE
The main objective of the study was to evaluate the effects of small increments in thyroxine (T4) levels following levothyroxine (L-T4) administration on the body composition of women patients. The secondary objective was to assess the effect of the therapy on energy expenditure and muscular function.


METHODS
The prospective, randomized study consisted of a 12-month follow-up of 37 women with thyroid nodules. The patients were divided into two groups for comparison, one treated with L-T4 (20 women) and the other untreated (17 women). L-T4 dose was individually adjusted to obtain a serum thyroid-stimulating hormone in the lower portion of the normal range. Multiple tests, including bioelectrical impedance analysis, dual-energy X-ray absorptiometry, air displacement plethysmography, measurement of waist circumference, and skinfold anthropometry, were used to investigate the muscular, fat, and water compartments; energy expenditure and muscular function were assessed by cycle ergometry.


RESULTS
There were no significant differences in body composition, heart rate, energy metabolism, or muscular function between the group of women treated with L-T4 and the untreated group.


CONCLUSIONS
The controlled increase of circulating T4 does not appear to modify the body composition or muscular function in women patients.
Dubois
Séverine
S
Pôle de maladies métaboliques et médecine interne; Centre Hospitalier Universitaire d'Angers, Angers Cedex 01, France.
Abraham
Pierre
P
Rohmer
Vincent
V
Rodien
Patrice
P
Audran
Maurice
M
Dumas
Jean-François
JF
Ritz
Patrick
P
D000328:Adult; D001823:Body Composition / Q000187:drug effects*; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000187:drug effects / Q000503:physiopathology*; D011446:Prospective Studies; D016606:Thyroid Nodule / Q000188:drug therapy / Q000503:physiopathology*; D013974:Thyroxine / Q000494:pharmacology* / Q000627:therapeutic use
D013974:Thyroxine