Why Am I So Tired?: Is your thyroid making you ill?An essential guide to how an underactive thyroid could be the root of your health problems. Why am I so Tired? questions the problems associated with an underactive thyroid. Mild hypothyroidism affects about 7 10 % of the population, but is frequently misdiagnosed because the symptoms are similar to that of ME, chronic fatigue, depression, and menopausal symptoms. Symptoms can include: exhaustion * weight gain * mental fogginess * low sex drive *