Functional capacity and muscular abnormalities in subclinical hypothyroidism.
BACKGROUND
Neuromuscular abnormalities and low exercise tolerance are frequently observed in overt hypothyroidism, but it remains controversial if they can also occur in subclinical hypothyroidism (sHT). The aim of this study is to evaluate neuromuscular symptoms, muscle strength, and exercise capacity in sHT, compared with healthy euthyroid individuals.


METHODS
A cross-sectional study was performed with 44 sHT and 24 euthyroid outpatients from a university hospital. Neuromuscular symptoms were questioned. Muscle strength was tested for neck, shoulder, arm, and hip muscle groups, using manual muscle testing (MMT). Quadriceps muscle strength was tested with a chair dynamometer and inspiratory muscle strength (IS) by a manuvacuometer. Functional capacity was estimated based on the peak of oxygen uptake (mL/kg/min), using the Bruce treadmill protocol.


RESULTS
Cramps (54.8% versus 25.0%; P < 0.05), weakness (45.2% versus 12.6; P < 0.05), myalgia (47.6% versus 25.0%; P = 0.07), and altered MMT (30.8% versus 8.3%; P = 0.040) were more frequent in sHT. Quadriceps strength and IS were not impaired in sHT and the same was observed for functional capacity. IS was significantly lower in patients complaining of fatigue and weakness (P < 0.05) and tended to be lower in those with altered MMT (P = 0.090).


CONCLUSIONS
Neuromuscular complaints and altered MMT were significantly more frequent in sHT than in controls, and IS was lower in patients with these abnormalities. Results suggest that altered muscle strength by MMT and the coexistence of neuromuscular complaints in patients with sHT may indicate neuromuscular dysfunction.
Reuters
Vaneska S
VS
Division of Endocrinology Department of Internal Medicine, University Federal of Rio de Janeiro, Rio de Janeiro, Brazil. vsreuters@yahoo.com.br
Teixeira
Patrícia de Fátima S
Pde F
Vigário
Patrícia S
PS
Almeida
Cloyra P
CP
Buescu
Alexandre
A
Ferreira
Márcia M
MM
de Castro
Carmen L N
CL
Gold
Jaime
J
Vaisman
Mario
M
D000328:Adult; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005080:Exercise Test; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue; D018908:Muscle Weakness; D018482:Muscle, Skeletal / Q000503:physiopathology; D013972:Thyrotropin / Q000097:blood
D013972:Thyrotropin