It can be hard to diagnose thyroid issues because the symptoms are often vague and overlap with other conditions. For example, fatigue, weight gain, and feeling cold all could be symptoms of a thyroid issue or several other diseases.
The only way to know for sure if someone has a thyroid issue is to have a blood test done. The most common test used to measure thyroid function is the TSH (thyroid-stimulating hormone) test. However, this test doesn’t always give an accurate picture of how well the thyroid is functioning. So in some cases, it may be necessary to do other tests as well.