Figure 1: Schematic representation of endocrine system. Glands with primary endocrine function are pituitary gland, hypothalamus, pineal gland, thyroid and parathyroid glands, thymus, adrenal glands, pancreatic islets and gonads; organs showing secondary endocrine functions are heart, kidneys, adipose tissue and gastrointestinal tract (colored by Irene Mandrich).