If there's one thing we know for sure about the thyroid, it's that shit's complicated.The butterfly-shaped gland in your neck is normally responsible for producing hormones that help regulate your metabolism, temperature, and your heart rate, among other things. And when it becomes either overactive or underactive, the thyroid can cause a range of symptoms (from unexplained weight loss or weight gain to mood issues) that are easily confused with other conditions. Oh, and thyroid problems are up to 10 times more common in women than men — though no one is sure why.Problems with your thyroid may actually start with the brain's pituitary gland, explains Dorothy Fink, MD , an endocrinologist and assistant professor of medicine at NYU Langone Medical Center. That's because your pituitary gland produces what's called thyroid-stimulating hormone (TSH). When it's released, TSH causes the thyroid to produce two other important hormones, T3 and T4, which then travel through your bloodstream to the rest of your body. These hormones together influence a huge variety of your body's processes. "There are thyroid hormone receptors on many different organs, not just on the gland in the neck," Dr. Fink adds. "So it does have far-reaching effects."And then, there's diagnosis, which can also be tricky. For starters, there's some uncertainty about the ideal level of thyroid-stimulating hormone (TSH) in your blood. A normal level is between 0.5 and 4.5, but hypothyroidism (the technical term for an underactive thyroid), for example, isn't diagnosed until you're at 10, Dr. Fink explains.This means that even if you don’t have an obvious issue, you may have a "subclinical" problem if you're in in the limbo between 4.5 and 10. Because your TSH results can also vary from test to test, it's a good idea to make sure your doctor is doing more than one and keeping tabs on your T3 and T4 levels as well.Once you're diagnosed, though, treatment is fairly straightforward. "The most common cause of a thyroid issue is an autoimmune problem," says Dr. Fink. With hypothyroidism, that means patients have antibodies that attack the thyroid and kill off its cells, which decreases the production of thyroid hormone. And with hyperthyroidism (an overactive thyroid), Graves' disease is the most common culprit. In this case, your antibodies cause an overproduction of thyroid hormones. Both diseases can be managed with medications that, unfortunately, usually need to be taken for the rest of a patient's life. In more extreme cases, surgery to remove the thyroid may be the best option.Ahead, we talk to Dr. Fink about five unexpected areas of your life in which your thyroid plays a role — and the specific clues that something might be off.