9. Muscle and Joint Weakness
When you have low thyroid levels, your metabolic switch flips toward catabolism. That’s when the body breaks down muscle tissue for energy rather than fat. Muscle strength decreases and leads to feelings of weakness. The process can also cause aches.
The reason that this same symptom occurs in patients with overactive thyroid glands is less clear. However, researchers suspect that excessive thyroid hormone levels can cause increased muscle protein degradation and muscle energy use. That will leave your muscles feeling sapped and weak.