Hormones are chemical messengers that travel around the body and control many different functions such as breaking down food to make energy and regulating periods. Sometimes hormones can go wrong and problems arise. For example when insulin (a hormone controlling the gut using carbohydrate to produce energy efficiently) is not produced, or stops working well, the patient develops diabetes. This is the most common serious problem related to hormones. There are many others though and their symptoms tend to be quite non-specific. This section also includes information on the thyroid gland (“Why am I always cold and tired?”) and polycycstic ovary syndrome (“Why haven’t I had a period for 3 months?”) as well as conditions such as Cushing’s syndrome and Addison’s disease. You can read all about the symptoms and check the treatments in our doctor-authored leaflets.