endokrin

Endokrin, or the endocrine system, comprises glands and tissues that produce hormones—chemical messengers released into the bloodstream to regulate distant organs and processes. The term comes from Greek roots meaning within and to secrete.

The principal components include the hypothalamus and pituitary gland, often described as the regulatory hub; the thyroid, parathyroid, and adrenal glands; the pancreas; and the gonads (ovaries and testes). Additional hormone-secreting cells are found in the gut, adipose tissue, heart, and other organs.

Hormones bind to specific receptors on target cells, triggering cellular responses. Most endocrine signaling uses feedback mechanisms; negative feedback is common, helping keep systems within a healthy range. The hypothalamic-pituitary axis coordinates many hormonal outputs.

Functions encompass metabolism and energy use, growth and development, reproduction, stress response, calcium and fluid balance, and circadian rhythms.

Disorders of the endocrine system arise from hormone deficiency, excess, or resistance. Common conditions include diabetes mellitus, thyroid disorders (hypothyroidism and hyperthyroidism), adrenal disorders, pituitary abnormalities, and gonadal dysregulation. Treatments include hormone replacement, drugs that alter production or action, and surgery when needed.

Endocrinology emerged in the early 20th century, with the term hormone introduced by William Bayliss and Ernest Starling in 1905, and the field has since advanced into diagnostic testing and targeted therapies.