Functional capacity and muscular abnormalities in subclinical hypothyroidism

Area of Science:

• Endocrinology
• Neurology
• Exercise Physiology

Background:

• Overt hypothyroidism commonly presents with neuromuscular issues and reduced exercise tolerance.
• The presence of these symptoms in subclinical hypothyroidism (sHT) remains debated.
• This study investigates neuromuscular symptoms, muscle strength, and exercise capacity in sHT patients.

Purpose of the Study:

• To compare neuromuscular symptoms, muscle strength, and exercise capacity between subclinical hypothyroidism patients and euthyroid controls.
• To identify potential neuromuscular dysfunction in subclinical hypothyroidism.

Main Methods:

• A cross-sectional study involving 44 sHT and 24 euthyroid outpatients.
• Neuromuscular symptoms were assessed via questionnaires.
• Muscle strength evaluated using manual muscle testing (MMT), dynamometry, and manuvacuometry for inspiratory strength (IS).
• Functional capacity measured by peak oxygen uptake (VO2 peak) using the Bruce treadmill protocol.

Main Results:

• sHT patients reported significantly higher frequencies of cramps, weakness, and altered MMT compared to controls.
• Quadriceps strength, inspiratory strength (IS), and functional capacity were not significantly different between groups.
• IS was lower in sHT patients reporting fatigue and weakness.

Conclusions:

• Neuromuscular complaints and altered MMT are more prevalent in subclinical hypothyroidism.
• Reduced IS in symptomatic sHT patients suggests potential neuromuscular dysfunction.
• MMT and symptom assessment may indicate neuromuscular impairment in sHT.