The endocrine system regulates important body functions through glands that secrete hormones directly into the bloodstream. The major glands include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries, testes, and pineal gland. These glands work together to regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood. Imbalances in endocrine system hormones can result in issues like hypercalcemia, which occurs when calcium levels in the blood are too high due to overactivity of the parathyroid glands.

1. Endocrine System Chapter 11