Shanaya, a 30 year old working mother was lately saying that she felt extremely tired, had put on a few kilograms and did not feel like eating. So she consulted her local doctor who, referred her to an endocrinologist and asked her to get her thyroid functions evaluated. Here is everything you need to know about the thyroid function test. What is thyroid function? Thyroid tests are usually ordered when you experience one or more of the following symptoms. Tremors, Increased heart rate, Dry skin, Hair loss, Weight gain or loss, Difficulty in sleeping, Anxiety, Abnormal periods and, Intolerance to cold.