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ABNORMALITIES OF THYROID FUNCTION Dr. Shaikh Mujeeb Ahmed Assistant Professor AlMaarefa College ENDO BLOCK 412
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Objectives The student should be able to: Describe the etiology, symptoms and treatment of thyrotoxicosis and hypothyroidism.
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Abnormalities Hypothyroidism – Deficient thyroid hormone secretion Hyperthyroidism Excess thyroid hormone secretion
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Hypothyroidism Primary failure of thyroid gland itself Secondary to deficiency of TRH, TSH or both. From an inadequate dietary supply of iodine.
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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.
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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
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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.
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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).
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Cretinism
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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)
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Fig. 19-4, p. 696
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Fig. 19-5, p. 697
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Anti thyroid drugs Surgical removal Administration of radioactive iodine
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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.
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Causes of Goiter Iodine deficiency Graves' disease Hashimoto's disease Multinodular goiter Solitary thyroid nodules Thyroid cancer Pregnancy Inflammation Fig. 19-6, p. 697
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Table 19-1, p. 696
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Synthesis, storage, and secretion of thyroid hormone Thiocynate X X Thiouracil
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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
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References Human physiology, Lauralee Sherwood, seventh edition. Text book physiology by Guyton &Hall,11 th edition. Text book of physiology by Linda.S.Costanzo third edition 19
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