hormons

Hormons are signaling molecules produced by endocrine glands and certain tissues that coordinate physiological processes by acting at distant targets. They are released into the bloodstream or extracellular fluid and influence specific cells that possess appropriate receptors, producing effects that can be rapid or long-lasting.

Chemical classes include peptide and protein hormones (such as insulin and growth hormone), steroid hormones (such as cortisol, estrogen, and testosterone), and amine hormones (such as adrenaline and thyroid hormones). Their structures determine how they are synthesized, stored, released, and how they interact with receptors.

Major sources include the pituitary, hypothalamus, thyroid, parathyroid, adrenal glands, pancreas, and gonads, with many tissues producing local or circulating hormones. Secretion is regulated by feedback systems, notably the hypothalamic–pituitary axis, and can be affected by circadian rhythms, stress, nutrition, and disease.

Receptors mediate action: lipophilic hormones cross cell membranes and bind intracellular receptors, influencing gene expression, while hydrophilic hormones bind surface receptors and trigger signaling cascades. Interactions among hormones create integrated networks.

Transport and clearance vary; many hormones are bound to carrier proteins in the blood, while others circulate freely. They are typically degraded by the liver or kidneys and excreted. Disorders of hormone production or action include diabetes, thyroid disease, adrenal disorders, and reproductive dysfunction.