What is a common complication of untreated hyperthyroidism?

Untreated hyperthyroidism can lead to a variety of complications, significant among which are osteoporosis and cardiac arrhythmias.

In hyperthyroidism, the overproduction of thyroid hormones can accelerate bone turnover, leading to increased bone resorption. This happens because thyroid hormones stimulate osteoclast activity, which can weaken bones and predispose individuals to osteoporosis—a condition where bones become fragile and more susceptible to fractures.

Moreover, hyperthyroidism affects the cardiovascular system by increasing heart rate and enhancing contractility, which can lead to cardiac arrhythmias, such as atrial fibrillation. These arrhythmias are dangerous as they can increase the risk of stroke and heart failure due to ineffective blood pumping and higher chances of thrombus formation.

Muscle weakness and fatigue are indeed symptoms associated with hyperthyroidism, but they are not the long-term complications resulting from untreated conditions. Weight gain, on the other hand, is generally not associated with hyperthyroidism; in fact, it typically causes weight loss due to increased metabolism. Thus, the combination of osteoporosis and cardiac arrhythmias distinctly characterizes the serious complications that can occur if hyperthyroidism is not properly managed.