19811 - THYROID DISORDERS Abdelaziz Elamin. MD, PhD, FRCPCH...

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Unformatted text preview: THYROID DISORDERS Abdelaziz Elamin. MD, PhD, FRCPCH Professor of Child Health Consultant Pediatric Endocrinologist Sultan Qaboos University, Oman HYPOTHYROIDISM-EPIDEMIOLOGY Neonatal screening reveals incidence that varies between 1-5/1000 live births The most common cause of preventable mental retardation in children Both acquired & congenital forms are linked to iodine deficiency Diagnosis is easy & early treatment is beneficial ETIOLOGY CONGENITAL Hypoplasia & mal-descent Familial enzyme defects Iodine deficiency (endemic cretinism) Intake of goitrogens during pregnancy Pituitary defects Idiopathic ETIOLOGY /2 ACQUIRED Iodine deficiency Auto-immune thyroiditis Thyroidectomy or RAI therapy TSH or TRH deficiency Medications (iodide & Cobalt) Idiopathic KILPATRIK GRADING OF GOITRE Grade 0: Not visible neck extended & Not palpable Grade 1: Not visible, but palpable Grade 2: Visible only when neck is extended & on swallowing, Grade 3: Visible in all positions Grade 4: Large goiter THYROID GLAND Derived from pharyngeal endoderm at 4/40 Migrate from base of the tongue to cover the 2&3 tracheal rings. Blood supply from ext. carotid & subclavian and blood flow is twice renal blood flow/g tissue. Starts producing thyroxin at 14/40. OVERVIEW (2) Maternal & fetal glands are independent with little transplacental transfer of T4. TSH doesnt cross the placenta. Fetal brain converts T4 to T3 efficiently. Average intake of iodine is 500 mg/day. 70% of this is trapped by the gland against a concentration gradient up to 600:1 THYROID HORMONES Iodine & tyrosine form both T3 & T4 under TSH stimulation. However, 10% of T4 production is autonomous and is present in patients with central hypothyroidism. When released into circulation T4 binds to: Globulin TBG 75% Prealbumin TBPA 20% Albumin TBA 5% THYROID HORMONES (2) Less than 1% of T4 & T3 is free in plasma....
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This note was uploaded on 02/23/2012 for the course PHARM 290 taught by Professor Staff during the Fall '10 term at Rutgers.

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19811 - THYROID DISORDERS Abdelaziz Elamin. MD, PhD, FRCPCH...

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