ABNORMALITIES OF THYROID FUNCTION

1. ABNORMALITIES OF THYROID FUNCTION ENDO BLOCK 412 Dr. ShaikhMujeeb Ahmed Assistant Professor AlMaarefa College

2. Objectives • The student should be able to: • Describe the etiology, symptoms and treatment of thyrotoxicosis and hypothyroidism.

3. Abnormalities • Hypothyroidism • Deficient thyroid hormone secretion • Hyperthyroidism • Excess thyroid hormone secretion

4. Hypothyroidism • Primary failure of thyroid gland itself • Secondary to deficiency of TRH, TSH or both. • From an inadequate dietary supply of iodine.

5. 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.

6. 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

7. 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.

8. 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).

9. Cretinism

10. 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 • ↑ Heart rate • ↑COP • Irritable, tense, anxious • Exophthalmos (bulging eyes) (grave’s disease)

11. Fig. 19-4, p. 696

12. Fig. 19-5, p. 697

13. Anti thyroid drugs • Surgical removal • Administration of radioactive iodine

14. GOITER • A goiter is an enlarged thyroid gland. • Occurs when either TSH or TSI excessively stimulates the thyroid gland.

15. Fig. 19-6, p. 697

16. Table 19-1, p. 696

17. Synthesis, storage, and secretion of thyroid hormone Thiouracil Thiocynate X X

18. 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

19. 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