The pituitary(下垂体), thyroid(甲状腺), and adrenal(副腎)glands are all part of the endocrine(内分泌の)system, a bodily system that is instrumental(助けになる、役立つ)in regulating metabolism(新陳代謝), tissue function, and growth and development. The endocrine system is an integrated network of small glands located throughout the body that release extracellular(細胞外の)signaling molecules known as hormones. Hormones travel in the blood to distant targets, where they cause specific physiological(生理的な)responses.