甲状腺功能减退Hypothyroidism 复旦大学医学院内分泌科李益明Hypothalamic-pituitary-thyroid axis Overview Clinical syndrome Slowing down of metabolism Slowing of growth and mental retardation in infants and children Generalized slowing down of organism Deposition of glycosaminoglycans in skin and muscle Reversible with therapy Etiology and Classifcation Primary(thyroid failure) Hashimoto’s thyroiditis Iodide deficiency or excessive Radioactive iodine therapy for GD Subtotal thyroidectomy Subacute thyroiditis Secondary: pituitary deficit Tertiary: hypothalamic dysfunction Peripheral resistance to thyroid hormone Pathogenesis Affects each tissue Accumulation of glycosaminoglycans (hyaluronic acid) Not to excessive synthesis But decreased destrution Increased capillary permeability Interstitial edema Skin Heart muscle Striated muscle Clinical Features Adults Symptoms Easy fatigability Coldness Weight gain Constipation Menstrual irregularities Signs Cool, rough, dry skin Puffy face and hands Hoarse and husky voice Slow reflexes Yellowish color skin Clinical Features Cardiovascular signs Impaired myocardium contraction Bradycardia Diminished cardiac output ECG: low voltage of QRS, P, T waves Pericardial effusion Coronary artery disease Cardiac angina(Replacement therapy aggravate ) Clinical Features Pulmonary function Shallow, slow respiration Respiratory failure Intestinal peristalsis Markedly slowed Constipation Renal function Decreased glomerular filtration Clinical Features Anemia Impaired hemoglobin synthesis Menorrhagia and Absorption of iron Folate deficiency Pernicious anemia Nuromuscular system Muscle weakness Slow reflexes Central nervous system symptoms Inability to concentrate Anovulatory cycles and infertility Depressed Symptoms of hypothyroidism  Symptoms  % of cases Weakness  99 Dry skin  97 Coarse skin  97 Lethargy 91 Slow speech 91 Edema of eyelids 90 Sensation of cold 89 Decreaseed sweeting  89 Cold skin  83 Thick tongue  82 Edema of face 79 Coarseness of hair  76 Pallor of skin  67 Memory impairment 66 Symptomsof hypothyroidism  Symptoms  % of cases Constipation 61 Gain in weight 59 Loss of hair  57 Pallor of lips 57 Dyspnea  55 Peripheral edema  55 Hoarseness or aphonia 52 Anorexia 45 Nervousness 35 Menorrhagia 32 Palpitation 31 Deafness 30 Precordial pain 25 Myxedema coma Frequently in obese elderly woman Yellowish skin Large tongue Thin hair Bradycardia Marked hypothermia Lethargy progressing to stupor or coma Hypoventilation Hypotension Shock Cretinism Etiology Low iodide intake and endemic goiter Ectopic thyroid gland TSH-R Ab[block] from mother Inherited defects in thyroid hormone Iodide,antithyroid drugs,radioactive iodine Symptoms Respiratory difficulty Cyanosis Jaundice Poor feeding Hypothroidism in childen Retarded growth Mental retardation Precocious puberty Face of hypothyroidism Face of hypothyroidism Laboratory Findings FT4: uTSH: sensitive to detect 0.01  u/mL Most sensitive Most convenient Most specific FT3: Variable May be within the normal range TPOAb 、TgAb ：AITD (autoimmune thyroid disease) TC Diagnosis Treatment Drugs for hypothyroidism  LT4 Desiccated thyroid 	 Component  T4 T4+T3 high ratio of T3 to T4 Dose 50  g  40mg Intensity 50 g = 30mg Initial dosage 25~50 g 20mg Maintenaning dosage 50~150 g  40~120mg Half-life 7 days  1 days	 Institution of replacement therapy Full adrenal support first if with concomitant adrenal insufficiency Beginning with low dosage Degress of hypothyroidism Age General health Increase tablet weekly Needs 6 weeks before equilibration Use powdered thyroid gland for myxedema coma Monitoring FT4 and TSH TSH will be suppressed in normal range in 3 mo Side effects No allergy Overdosage Arrhythmia Paroxyamal atrial tachycardia fibrillation Insomnia Tremor Restleness Excessive warmth * * Symptoms+Signs Primary hypothyroidism TRH test FT4 +TSH Secondary hypothyroidism Normal type response Excessive response No response Pituitary lesion Hypothalamic lesion FT4 +TSH or N Primary hypothyroidism If ?