Endocrine

Endocrine refers to the system of glands and tissues that secrete hormones into the bloodstream to regulate distant organs and processes. Hormones are chemical messengers that alter target cell activity by binding to specific receptors, triggering signaling cascades that influence metabolism, growth, development, and homeostasis.

Endocrine glands include the pituitary, thyroid, parathyroid, adrenal, pineal, pancreas, and gonads, among others, as well as dispersed cells in organs such as the gut and fat tissue. Unlike exocrine glands, which secrete through ducts to surface or cavities, endocrine glands release hormones directly into the circulatory system. The hypothalamus in the brain coordinates the endocrine system by signaling the pituitary gland, the master gland, which in turn releases hormones that regulate other glands.

Hormones can be peptide or protein, amine, or steroid in chemical class. They reach targets via blood and act through cell-surface receptors (often triggering second messenger systems) or intracellular receptors (as with lipid-soluble steroids). Regulation commonly occurs through negative feedback, maintaining hormone levels within a stable range; positive feedback exists in specific situations such as oxytocin during parturition and certain hormonal axes.

Endocrine function supports many biological processes: metabolism, stress response, reproduction, growth, and fluid and electrolyte balance. Disorders include hypo- or hyperfunction of glands, leading to conditions like diabetes mellitus, thyroid disease, and adrenal disorders. Diagnosis relies on clinical assessment and hormone measurements; treatment may involve hormone replacement, antagonists, or education and lifestyle adjustments.