Endocrinology (3 lectures) PDF

(3 lectures) Dr Rabia Latif Objectives  Introduction to Endocrinology  Endocrinal control of Growth  Endocrinal control of fuel metabolism  Endocrinal control of calcium metabolism  Stress Hormones  The Endocrine system consists of the ductless endocrine glands. (endo means “internal”)...

(3 lectures) Dr Rabia Latif Objectives  Introduction to Endocrinology  Endocrinal control of Growth  Endocrinal control of fuel metabolism  Endocrinal control of calcium metabolism  Stress Hormones  The Endocrine system consists of the ductless endocrine glands. (endo means “internal”); crine means “ secretion”) Endocrine glands are responsible for the secretion of hormones Hormones  Hormone is a chemical released from Glands.  Properties Secreted in very small amounts Transported, usually, in the blood Travels some distance to target tissues Target cells have specific receptors Regulates cell reactions to have a biological effect Secretes sex hormones a. Endocrinal control of Growth What do we mean by growth?  Increase in the number and size of the cells  It involves lengthening of the skeleton (particularly the long bones of the legs and the vertebral column), but also the increase in size of all soft tissues (internal organs). Hormones involved in Growth  Growth Hormone (GH) (secreted from the Pituitary Gland)  Cause an increase in the number and size of the cells of soft tissues and skeleton  Size of the cells increase due to Protein synthesis.  Thyroid Hormone (secreted from the Thyroid Gland)  Secretion of Growth hormone requires the normal plasma levels of thyroid hormones.  Thyroid hormones increase the number of receptors for GH.  Insulin (secreted from the Pancreas)  Sex hormones (secreted from the testes and ovaries)  Cortisol (secreted from the Adrenal Gland, Cortisol is an anti-growth hormone) Metabolic and growth-promoting actions of Growth Hormone Growth hormone hypo- Growth hormone hyper- secretion secretion (Dwarfism) (Gigantism) Role of Thyroid Hormone in growth (1)  Inside the uterus, skeletal Growth of fetus independent of Thyroid hormones  from 28 weeks of pregnancy to one week postpartum (after delivery) Thyroid hormone is ABSOLUTELY required for normal development of the CNS.  Thyroid hormone from MOTHER available to fetus early in pregnancy Role of Thyroid Hormone (contd.)  Thyroid hormone has a role in GH synthesis and release.  Also it increases the number of GH receptors.  HYPOTHYROID children fail to grow to normal stature because of the relative GH deficiency that is present (Cretinism is congenital (since birth) hypothyroidism in children)  Cretinism: HYPOTHYROID child leading to short stature and less mental development  Myxedema: HYPOTHYROID adults develop swelling of face (myxedema) Hypothyroidism Myxedema Cretinism Role of Sex Hormones in growth  Estrogen, progesterone and testosterone.  Growth spurt at puberty is dependent on the availability of the sex hormones (probably estrogen in both females and males)  Stimulates growth of long bones, but also closure of the epiphyseal plates Role of Insulin & Cortisol in growth  Growth to normal stature requires normal availability of insulin and response to insulin, and normal cortisol levels.  High levels of cortisol will reduce growth because Cortisol is an anti-growth hormone.  Anti-growth effects of Cortisol:  Cortisol causes Protein breakdown  Cortisol blocks secretion of Growth hormone.  Children living under stressful environment have less growth due to high levels of Cortisol. b. Endocrinal control of fuel metabolism Hormones related with fuel metabolism  Hyperglycemia (Diabetes Mellitus) Comparison of type1 & type 2 Diabetes Mellitus Characteristic Type 1 Diabetes Type 2 Diabetes Level of Insulin secretion None or almost none May be normal or exceed normal Typical age of onset childhood adulthood Percentage of diabetics 10-20% 80-90% Basic defect Destruction of B cells Reduced sensitivity of insulin’ target cells (decrease insulin receptors) Decrease Glut 4 Obesity association No usually Genetic & environmental Yes Yes factors importance Ketosis Common if untreated Rare Treatment Insulin injections Dietary control dietary management weight reduction exercise exercise oral hypoglycemic drugs Metabolic effects of Thyroid hormone (TH)  It regulates of Basal Metabolic Rate (BMR).  Increases oxygen consumption in most target tissues.  TH increases sensitivity of target tissues to catecholamines (epinephrine & norepinephrine), leading to increased heart rate, increased heart contraction and rapid breathing.  Hyperthyroidism: Hypersecretion of Thyroid Hormone (Prominent eyes)  Cushing syndrome: Cortisol hyper-secretion (moon face) Estrogen Actions  Promotes fat deposition  Increases bone density  Closes the epiphyseal plates  Improves blood lipid profile by increasing high density lipoproteins (HDL; Good cholesterol) and decreasing low density lipoproteins (LDL; Bad cholesterol)  Promotes vasodilation by increasing nitric oxide production in arterioles (cardioprotective effect) c. Endocrinal control of calcium metabolism Regulation of Calcium Metabolism  Regulation of Ca+2 metabolism depends on hormonal control of exchanges between the ECF and :  bone  kidneys  intestine  The hormones controlling this exchange are:  Parathyroid hormone (PTH)  Calcitonin  Vit-D3  Rickets (Vitamin D Tetany (hand muscle spasm leading to deficiency in children); flexion at the wrist joint and extension of the fingers) Legs become curved Tetany is produced due to Calcium deficiency Stress Hormones Stress Hormones  Cortisol  Adrenaline (epinephrine)  Noradrenaline (nor-epinephrine) Cortisol Increased levels of cortisol could trigger 1. high blood pressure 2. increased levels of blood sugars 3. increased respiratory rate and heart rate 4. Cortisol can also inhibit the immune system