23 Symptoms That Could Indicate Hyperthyroidism

14. Muscle Weakness, Especially in the Upper Arms and Thighs

Many people associate muscle fatigue with overexertion, but hyperthyroidism can quietly weaken large muscle groups over time—especially in the shoulders, upper arms, and thighs. Tasks like climbing stairs, lifting groceries, or even blow-drying your hair can suddenly feel unusually difficult. This is because the accelerated metabolism breaks down muscle tissue faster than the body can rebuild it. If you're losing muscle tone despite staying active, or feel unexpectedly shaky during everyday movements, your thyroid could be the hidden culprit.