Cretinsm
- 2. THYROID GLAND It is endocrine gland which drain secretion into blood stream directly. It locates in the neck Consists of two lobes connected by isthmus Secret t3 and t4 hormones
- 3. Thyroid Gland stroma C.T capsule Trabeculae Reticular C.t parenchyma Thyroid Follicles Principle follicular cells Para follicular C cells Inter follicular cells HISTOLOGY OF THYROID GLAND
- 4. THYROID FOLLICLE Spherical in shape. Lined by two types of cells: 1- principle follicular cells . secret T3 and T4 hormones. 2- Para follicular C cells. secret calcitonin. Contain acidophilic colloid in the center which contain stored hormones.
- 14. SYNTHESIS OF THYROID HORMONE
- 17. FUNCTIONS OF THYROID HORMONES Metabolic effect: (generally increase BMR.) on CHO metabolism: - increase absorption of CHO from GIT . - enhance gluconeogenesis and glycolysis . on protein synthesis small dose of thyroid hormone increase rate of formation of proteins Large dose of thyroid hormone lead to catabolism of muscle protein On fat metabolism Accelerate lipolysis Lower the level of cholesterol , phospholipids and TAG
- 18. Thyroid hormone is necessary for hepatic conversion of carotene to vitamin A Effect on skeletal growth and development required for production and action of growth hormone and insulin like growth factor On nervous system Promotes growth and development of the brain during the fetal life for the first few years Essential for normal myelination of nervous system in infant On sexual functions Essential for normal menstrual cycles and fertility They increase milk secretion in lactating women
- 19. ON NERVOUS SYSTEM Thyroid hormone promoted growth and development of the brain during fetal life & for the first few years of life. The thyroid hormone are essential for normal myelination & development of the nervous system. In infant. If there is a deficiency in thyroid hormone growth & maturation of the brain is retarded, myelination is defective, the reflex time is prolonged. In adult, thyroid hormone causes an increased response of the brain to catecholamine & increase activation of reticular activating system. An excess of thyroid hormone leads to restlessness
- 20. ON SEXUAL FUNCTIONS For normal sexual function to act thyroid hormone secretion needs to be approximately normal. Thyroid Hs. Are essential for normal menstrual cycles and fertility. They increase milk secretion in lactating women. ON GASTRO INTESTINAL TRACT They increase the rate of secretion of the digestive juice and motility.This leads to increase appetite and food intake. On respiration Thyroid hormone increase respiration due to increase rate of metabolism which increase the utilization of oxygen & the formation of carbon dioxide.
- 21. THE CARDIOVASCULAR SYSTEM thyroid hormone increase the number & affinity of beta-1, adrenergic receptors in the heart, also it increase its sensitivity catecholamine (catecholamine increases all properties of the heart). Increased metabolism in the tissues causes more rapid utilization of oxygen & greater metabolic end products to be released from the tissues.These effects cause vasodilatation, thus increasing the rate of blood flow in the skin for heat elimination. Increase blood flow leads to increase venous return leading to increase in cardiac output so the systolic blood pressure thus, pulse pressure is increased. The hormone slightly increase the blood volume, partly from vasodilatation and partly secondary to its
- 22. CONGENITAL HYPOTHYROIDISM Definition: it is inadequate thyroid hormone production in newborn infants. Causes: 1- iodine deficiency. 2- Thyroid gland is absent or underdeveloped. 3-A hypoplastic gland may develop higher in the neck or even in the back of the tongue (lingual thyroid) 4- One common cause is the presence of
- 23. SYMPTOMS AND SIGNS Infants born with congenital hypothyroidism may show no effects, or may display mild effects that often go unrecognized as a problem. 1- excessive sleeping 2- reduced interest in nursing 3-, poor muscle tone 4- low or hoarse cry 5- infrequent bowel movements 6- exaggerated jaundice
- 24. DIAGNOSIS In the developed world, nearly all cases of congenital hypothyroidism are detected by the newborn screening program. These are based on measurement of TSH or thyroxine (T4) on the second or third day of life( Heel prick). If the TSH is high, or the T4 low, the infant's doctor and parents are called and a referral to a pediatric endocrinologist is recommended to confirm the diagnosis and
- 25. TREATMENT The goal of newborn screening programs is to detect and start treatment within the first 1–2 weeks of life. Treatment consists of a daily dose of thyroxine, available as a small tablet. The generic name is levothyroxine The tablet is crushed and given to the infant with a small amount of water or milk Within a few weeks, the T4 and TSH levels are rechecked to confirm that they are being normalized by treatment
- 27. CRETINISM is an old term for the state of mental and physical retardation. Result from: untreated congenital hypothyroidism Iodine deficiency
- 28. CLINICAL PICTURE 1) Full picture of Hypothyroidism. 2) Growth Retardation. A) PHYSICAL Skeletal growth is more affected than soft tissue growth Long bones (linear growth) are more affected than short bones Disproportionate Dwarfism. Delayed motor mile stones of development (sitting, walking) Delayed dentition + small teeth. Delayed closure of fontanels.
- 31. B) MENTAL Mental Retardation (permanent). C) SEXUAL Sexual retardation. TREATMENT: Replacement therapy (start very early).