Hyperthyroidism affects millions of people -- many of whom are unaware. Overactive thyroid affects more women than men, specifically women older than age 60, according to a 2009 study published in the Journal of Clinical Endocrinology Metabolism. Having a family history of thyroid problems, being anemic, pregnant or having delivered a child within the past six months, eating too many iodine-rich foods and atrial fibrillation can increase the risk of hyperthyroidism, according to the National Endocrine and Metabolic Diseases Information Services. 

The most common condition associated with hyperthyroidism is Graves' disease, a condition in which antibodies stimulate the thyroid and may cause overproduction of thyroid hormone. Those affected by this disease may have bulging eyes. Nodules or lumps in the throat referred to as goiters are another sign of a malfunctioning thyroid gland. Some may experience thick skin over the shin. 

Despite how common hyperthyroidism is, it often goes unreported or misinterpreted. Patients may not see their doctors, believing the symptoms are a sign of a less serious condition. It's important to receive regular examinations and report any symptoms to your doctor.