The thyroid gland is often referred to as the body’s engine, and just like the mechanical metaphor when the thyroid gland stops working properly the body eventually starts to sputter.

That’s why health care experts have designated January Thyroid Awareness Month, so that more people take the time to familiarize themselves with the symptoms of thyroid disease. According to the American Association of Clinical Endocrinologists (AACE), thyroid disease is a more common endocrine disorder than diabetes or heart disease and affects as many as 30 million Americans, more than half of whom remain undiagnosed.

The thyroid gland is a small, butterfly-shaped gland located in the base of the neck just below the Adam’s apple. Although small in size, the gland plays a large role by producing thyroid hormone which influences the function of many of the body’s most important organs, including the heart, brain, liver, kidneys and skin.

It’s when the gland’s hormone production is off kilter to one extreme or the other that physical problems start to arise, as is the case when there is either too much thyroid hormone in the system (which is called hyperthyroidism), or there is too little thyroid hormone production (hypothyroidism).

Hypothyroidism carries a range of symptoms that include unexplained fatigue ,weight gain, depression, forgetfulness, feeling cold, hair loss, low sex drive, constipation or infertility, says Nadia Yaqub, MD, an adjunct associate professor in the University of Cincinnati (UC) College of Medicine’s division of endocrinology, diabetes and metabolism.

Because hypothyroidism usually has insidious onset and nonspecific symptoms, Yaqub—a UC Health endocrinologist who treats patients with all spectrums of thyroid disease— says: “People don’t connect the dots right away” and the symptoms are easily brushed off and attributed to other factors such as poor diet, stress or even depression.

On the flip side,  the symptoms of hyperthyroidism—rapid heart rate, heat intolerance and unexplained weight loss and anxiety—manifest quickly and may cause people to seek medical attention sooner, she says.  According to the AACE, the most common cause of hyperthyroidism is Graves’ disease, where antibodies target the thyroid gland, causing it to overproduce thyroid hormone.

The majority of thyroid disease sufferers are women, often diagnosed by their OB/GYN when women are trying to conceive.  Thyroid hormone also plays role in infertility as well. Some females are diagnosed for the first time during their pregnancy.

For both hypothyroidism  and hyperthyroidism, medication is prescribed to bring hormone levels back into sync with established ranges, says Yaqub, who adds that hyperthyroidism is monitored more closely because it is  more acute and can cause heart palpitations, arrhythmias (abnormal heartbeat) and heart failure if remains undiagnosed and untreated.

Two other concerns surrounding the thyroid are thyroid nodules and thyroid cancer, which can occur independent of the above thyroid diseases, says Yaqub. Nodules are lumps or abnormal masses and can be caused by benign cysts, benign tumors or cancers of the thyroid, she says. Nodules may be single or multiple and differ in size; if too large they may impede nearby structures in the throat and cause swallowing and choking.

According to the AACE, about 60,000 cases of thyroid cancer are diagnosed yearly in the U.S. Thyroid cancer is far more common among adult women than men or youth and most cases of thyroid cancer has a good prognosis and high survival rates—especially when diagnosed in its early stages.

Although thyroid disease awareness has increased over the past decade, and more primary care physicians are screening for thyroid disease, Yaqub says she still sees patients with debilitating symptoms that could have easily been remedied by early diagnosis.