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ABNORMALITIES OF THYROID FUNCTION ENDO BLOCK 412 Dr. Shaikh Mujeeb Ahmed Assistant Professor AlMaarefa College Objectives • The student should be able to: • Describe the etiology, symptoms and treatment of thyrotoxicosis and hypothyroidism. Abnormalities • Hypothyroidism – Deficient thyroid hormone secretion • Hyperthyroidism • Excess thyroid hormone secretion Hypothyroidism • Primary failure of thyroid gland itself • Secondary to deficiency of TRH, TSH or both. • From an inadequate dietary supply of iodine. Clinical features • The symptoms of hypothyroidism are largely caused by a reduction in overall metabolic activity. • Reduced BMR (less energy expenditure at rest); • Displays poor tolerance of cold (lack of the calorigenic effect); • Tendency to gain excessive weight (not burning fuels at a normal rate); • Easily fatigued (lower energy production); • Slow, weak pulse (caused by a reduction in the rate and strength of cardiac contraction and a lowered cardiac output); and • Exhibits slow reflexes and slow mental responsiveness (because of the effect on the nervous system). The • Mental effects are characterized by diminished alertness, slow speech, and poor memory. Causes of congenital hypothyroidism • • • • Maternal iodine deficiency Fetal thyroid dysgenesis Inborn errors of thyroid hormone synthesis Maternal antithyroid antibodies that cross the placenta • Fetal hypopituitary hypothyroidism MYXEDEMA (Adult Hypothyroidism) Puffy appearance, primarily of face, hands, and feet Caused by infiltration of skin with complex water retaining carbohydrate molecules. Symptoms: The patient becomes sluggish both mentally and physically and often feels cold. The hair becomes dry and the skin becomes dry and waxy. The tissues of the face swell. Treatment: – If diagnosed early, can be treated by administrating of T4. – Exception, if hypothyroidism caused by iodine deficiency; treated by dietary iodine. Cretinism • Results from hypothyroidism from birth • Characterized by dwarfism & mental retardation as well as other general symptoms of thyroid deficiency. • At birth, child appears normal because thyroxine is received from mother through placenta • Symptoms: growth retardation, abnormal bone development, low body temperature, lethargy, severely mentally retarded (short limbs, a large protruding tongue, coarse dry skin, poor abdominal muscle, tone and an umbilical hernia). Cretinism HYPERTHYROIDISM • • • • • • • • • • • • • • The most common cause of hyperthyroidism is Graves’ disease. immune disease thyroid-stimulating immunoglobulin (TSI), also known as long-acting thyroid stimulator (LATS), ↑ BMR poor tolerance of heat Increased appetite body weight muscle weakness Muscle termers Sleep ↑ Heart rate ↑COP Irritable, tense, anxious Exophthalmos (bulging eyes) (grave’s disease) Fig. 19-4, p. 696 Fig. 19-5, p. 697 • Anti thyroid drugs • Surgical removal • Administration of radioactive iodine GOITER • A goiter is an enlarged thyroid gland. • Occurs when either TSH or TSI excessively stimulates the thyroid gland. • The most common cause of goiter worldwide is a lack of iodine in the diet. Causes of Goiter • • • • • Iodine deficiency Graves' disease Hashimoto's disease Multinodular goiter Solitary thyroid nodules • Thyroid cancer • Pregnancy • Inflammation Fig. 19-6, p. 697 Table 19-1, p. 696 Synthesis, storage, and secretion of thyroid hormone Thiouracil Thiocynate X X Antithyroid Substances • Thiocyanate Ions – Decrease Iodide Trapping – inhibition of the iodide-trapping mechanism • Propylthiouracil – Decreases Thyroid Hormone Formation Propylthiouracil & similar compounds as – methimazole and carbimazole – block the peroxidase enzyme • Iodides in high concentrations decrease thyroid activity and thyroid gland size References Human physiology, Lauralee Sherwood, seventh edition. Text book physiology by Guyton &Hall,11th edition. Text book of physiology by Linda .S .Costanzo third edition 19