Endocrinology: Non-endocrine Organs & Hormone Action

heart , kidney, GI Tract

the atrial wall of heart secretes a peptide hormone called atrial natriuretic factor (ANF) when blood increases ANF is secreted by the atrial walls of heart ANF causes dilation of the blood vessels and reduce the blood pressure (hypotensive)

juxta glomerular cells of kidney produce a peptide hormone called erythropoietin Erythropoietin stimulates erythropoiesis (formation of RBC) ,calcitriol -Active form of vitamin D which is synthesized by kidneys Calcitriol is required for dietary calcium absorption

gastro-intestinal tract secretes four major peptide hormones 1.Gastrin 2.secretin 3. cholecystokinin(CCK) 4. Gastric inhibitory peptide (GIP)

Gastric acts on gastric glands and stimulates the secretion of hydrochloric acid and pepsinogen secretin acts on the exocrine pancreas and stimulates secretion of pancreatic enzymes and bile juice, respectively. GIP inhibits gastric secretion and motility

growth factors are hormones secreted by several non endocrine tissues these factors are essential for normal tissues growth, tissue repair, tissue regeneration

hormones produce their effects on target tissues by binding to their specific protein receptors called hormone receptors located in the target tissues only ,membrane bound receptors - present in the target cell membrane, intracellular receptors - (present inside the target cell they are mostly nuclear receptors present inside the nucleus.) each receptors is specific to a perticular hormone only and hence receptors are specific A hormone can create effect in its target cell only after binding with its receptor in the target cell binding of a hormone to its receptor leads to the formation of a hormone - receptor complex Hormone-receptor complex formation leads to certain biochemical changes in the target tissue Target tissue metabolism and hence physiological functions are regulated by hormones

peptide, polypeptide, protein hormones eg:(insulin glucagon pituitary hormones hypothalamic hormones etc) steroids(eg: cortisol, aldosterone, testosterone, estradiol and progesterone) Iodothyronines(eg: Thyroid hormones) Amino acid derivatives (eg: Epinephrine)

They are lipophilic hormones they can cross the target cell membrane they use intracellular receptors their receptors are usually located inside the target cells and mostly inside the nucleus such hormones bind to their intracellular receptor to form Hormone-receptor complex and creates the required effect the hormone receptor complex formed interacts with the genome and regulate general expression or chromosome function cumulative biochemical actions result in physiological and developmental effects

Iodinates thyronines(T3 triiodothyronine ,T4 tetraiodothyronine) steroid hormones hormones of gonads (androgens, estrogen, progesterones) hormones of adrenal cortex (glucocorticoids, Mineralocorticoids,sex hormones)

they are hydrophilic hormones such hormones do not cross the target cell membrane they bind with their membrane bound receptor to form hormone receptor complex they generate secondary messengers to create the required effects in target cells eg:FSH

hormones that use membrane bound receptors regulate cellular metabolism

cyclic adenosine monophosphate(cAMP),ca2+,IP3(Inositol triphosphate) etc