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Lecture 21 on Endocrinology I

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Biological Sciences

BIOB30FALL2011 Lecture 21 Endocrinology 1Hormones Chemical messengers secreted directly into the blood stream by specialized calls known as endocrine glandscellscan be transported to distant targets because they are carried in the blood stream Exocrine glands example Salivary sweat mammary glands do not secrete hormonesHormones can have effects over minutes hours days weeks months Even at a low concentration there is still an effect nanomolar 109 to picomolar 1012Effects of hormones Growth and developmentMetabolismRegulation of internal environment ex Temperature and water balance ion movement ReproductionBinds to a receptor to cause a responseAct on multiple tissuesEffect on tissue depends on type of tissue and stage of development baby to teenager to adultThey are degraded to inactive metabolites by enzymes often in the liver and kidneysexcreted in urine and bile from the liverHalf life amount of time rewuired to decrease the concentration of hormone in the circulation by half 3 Chemical Classes of HormonesAmine HormonesAmine hormones are derived from tryptophan or tyrosine Small molecules which have a half life of secondsneeds to be continuously secreted for long duration of action Example melatonin and thyroid hormone 3 Chemical Classes of HormonesPeptide Hormones Synthesized from prepro hormone Most common hormonesAre made all over the bodyThey are lipophobicthe effect is caused by the hormones binding to a membrane receptor Activate second messenger cascades example cAMPCauses opening and closing of ion channels modulation of metabolic enzymes and transport proteinsprotein synthesisThey are fast actingHydrophilicwhich means they can be easily transported around the body They have a short half life minutesthey are secreted and broken down quickly in order to maintain homeostasis quickly 1Example pituitary and pancreatic hormonesPreprohormones contain 1 or more copies of peptide hormones large and inactive and come from ribosomes contain signal sequence which directs it to ribosomes on the endoplasmic reticumlum3 Chemical Classes of HormonesSteroid Hormones All steroid hormones are similar in structureLipophillicreceptor is inside target cells usually in the cytoplasm or the nucleusBind to DNA to activate or turn off protein synthesisSlower actingeffects last for a long period of time Half life is LONG example cortisol half life is of 6090 minutesNot solumble in plasma and body fluid hydrophobicso require carrier proteins for transport in circulation Some carrier proteins are specific example corticosteroid binding protein is specific for carrying cortisolAnd some are general plasma proteins such as albumin which can transport many steroid hormones Steroid hormones are made in the adrenal gland cortex gonads and placentaThey are synthesized in the smooth endolplasmic reticulum as they are requiredExample cortisol estrogen progesterone testosterone Primary Endocrine Glands The Adrenal Gland Specialized neuroendocrine tissue associated with the sympathetic nervous system The adrenal cortex secretes 3 steroid hormonesAldosterone mineralocorticoid controls water and Na retention in kidneysGlucocorticoidsexample cortisolSex hormonesexample androgens estrogen and progesterone PancreasControls digestion and absorption of nutrients2
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