Endocrinology is the field of hormone-related diseases. An endocrinologist can diagnose and treat hormone problems and the complications that arise from them. Hormones regulate metabolism, respiration, growth, reproduction, sensory perception, and movement. Hormone imbalances are the underlying reason for a wide range of medical conditions. Endocrinology focuses both on the hormones and the many glands and tissues that produce them. Humans have over 50 different hormones. They can exist in very small amounts and still have a significant impact on bodily function and development.