Endocrinology and the Endocrine System

Endocrine System: The endocrine system coordinates functioning between different organs through hormones, which are released into the bloodstream from specific types of cells within endocrine (ductless) glands. Once in circulation, hormones affect function of the target tissue. Some hormones exert an effect on cells of the organ from which they were released (paracrine effect), some even on the same cell type (autocrine effect). Hormones can be peptides of various sizes, steroids (derived from cholesterol), or amino acid derivatives. Hormones bind selectively to receptors located inside or on the surface of target cells. Receptors inside cells interact with hormones that regulate gene function (eg, corticosteroids, vitamin D, thyroid hormone). Receptors on the cell surface bind with hormones that regulate enzyme activity or affect ion channels (eg, growth hormone, thyrotropin-releasing hormone). Endocrinology: Simply put, endocrinology is the study of endocrine glands. Endocrine glands are a group of glands in the body which secrete hormones. The purpose of the secreted hormones is to evoke a specific response in other cells of the body which are located far away. The hormones are secreted into the blood stream giving them access to all other cells of the body. Endocrine Glands and Their Hormones Thyroid Gland: Located in the front of the neck. Thyroid gland secretes thyroid hormone, which regulates the body's overall metabolism. Parathyroid Glands: There are 4 parathyroid glands located behind the thyroid. They secrete parathyroid hormone, and have absolute control over calcium levels throughout the body. Adrenal Glands: There are 2 adrenal glands located on the top of each kidney. Inner part secretes adrenaline, outer part secretes aldosterone and cortisol. Adrenal glands maintain salt levels in the blood, maintain blood pressure, help control kidney function, control overall fluid concentrations in the body. Neuroendocrine Glands of the Pancreas: Located deep in the abdomen behind the stomach, the pancreas is primarily a digestive organ. It also contains extremely important endocrine cells which secrete: insulin, glucagon, somatostatin, and others. They control blood sugar and overall glucose metabolism, help control other endocrine cells of the digestive tract. Pituitary Gland: The pituitary is located at the base of the brain. Secretes thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), adrenocotropic hormone (ACTH), and others. It controls the activity of many other endocrine glands (thyroid, ovaries, adrenal, etc.).