The endocrine system regulates important body functions through hormones secreted by various glands. Key glands include the adrenal glands, ovaries, testes, pancreas, parathyroid and thyroid glands, pineal gland, and pituitary gland. These glands secrete hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep cycles, and other critical processes. Disorders of the endocrine system can affect hormone levels and the function of glands like the thyroid, leading to diseases such as diabetes, osteoporosis, infertility, and other conditions.