ABNORMALITIES OF THYROID FUNCTION ENDO BLOCK 412 Dr

ABNORMALITIES OF THYROID FUNCTION ENDO BLOCK 412 Dr. Shaikh Mujeeb Ahmed Assistant Professor Al. Maarefa 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 T 4. – 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 Ø Human physiology, Lauralee Sherwood, seventh edition. Ø Text book physiology by Guyton &Hall, 11 th edition. Ø Text book of physiology by Linda. S. Costanzo third edition 19