MODE OF ACTION OF DIFFERENT HORMONES ::
Actual mechanisms by which hormones produce the effects are not very clear however various mechanisms of action have been proposed Most hormones bind to their specific protein receptors on plasma membranes of target cells Steroids form complexes with cytoplasmic proteins which attach to nuclear receptors Thyroid hormone penetrates the cell to adhere to nuclear receptors These hormones which bind to nuclear receptors affect the synthesis of proteins The effect may be an increase or decrease in the synthesis of proteins
Hormones that bind to the receptors on plasma membranes may alter protein synthesis cellular permeability or the production of secondary messengers The common second messenger involved is cyclic adenosine 3-5 monophosphate (cAMP) This is a nucleotide which is formed by the activation of membrane bound enzyme adenylate cyclase when certain hormones bind to cell membrane receptors Increase in cAMP activates
Endocrine glands and their hormones ::
1.Pituitary (Anterior) Growth hormone (GH) Prolactin
Thyrotrophic hormone (TSH)
Follicle Stimulating hormone (FSH)
Leutenizing hormone (LH)
Adrenocorticotrophic hormone (ACTH)
Pituitary (Intermediate) Melanocyte stimulating hormone (MSH)
Pituitary (Posterior) Oxytocin Vasopressin
2.Thyroid Tri-iodo-thyronine (T3)
Thyroxine (T4) Calcitonin
3.Parathyroid Parathormone
4.Adrenal or suprarenal Glucocorticoids e.g. cortisone
mineralocorticoids e.g aldosterone
Sex-steroids e.g.progesterone
estrogen and androgens Adrenaline
5.Pancreas Glucagon insulin somatostatin
6.Testis Testosterone
7.Ovary Estrogen Progesterone
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