Hypothyroidism PDF

Lecture Material is adapted from © 2017 Wolters Kluwer Health, Lippincott Williams & Wilkins Applied Pathophysiology: A Conceptual Approach to the Mechanisms of Disease Chapter 13: Altered Hormonal and Metabolic Regulation Module 4: Clinical Models Dr. Romeo Batacan Jr. MPAT12001 Medical Pathoph...

Lecture Material is adapted from © 2017 Wolters Kluwer Health, Lippincott Williams & Wilkins Applied Pathophysiology: A Conceptual Approach to the Mechanisms of Disease Chapter 13: Altered Hormonal and Metabolic Regulation Module 4: Clinical Models Dr. Romeo Batacan Jr. MPAT12001 Medical Pathophysiology Lecture Series Copyright © 2017 Wolters Kluwer Health | Lippincott Williams &Wilkins  Hypothyroidism Pathophysiology Clinical manifestations Diagnostic criteria Treatment  Hypothyroidism Hypothyroidism: deficient production of TH by the thyroid gland Hypothyroidism is the most common disorder of thyroid function it affects between 0.1% and 2% of individuals in the United States more common in women and the elderly 1. Congenital: develops prenatally and present at birth 2. Acquired: develops later in life Primary hypothyroidism most prevalent Central (secondary) hypothyroidism much less common pituitary or hypothalamic failure with failure to stimulate normal thyroid function Subclinical hypothyroidism is mild thyroid failure elevation in TSH level with normal levels of circulating TH treatment is not warranted  Hypothyroidism Pathophysiology Congenital hypothyroidism: lack of thyroid gland development lack of appropriate synthesis of thyroid hormone problems with TSH secretion In utero maternal T4 crosses the placenta the newborn appears unaffected at birth untreated after birth >> lack of thyroid hormone production and secretion mental retardation and impaired growth: cretinism neonatal screening: detects congenital hypothyroidism treatment with thyroid hormone replacement McCance KL, Huether S. Pathophysiology. 7th ed. N.S.W, Mosby; 2015  Hypothyroidism Pathophysiology Acquired deficiency of thyroid hormone (TH) from: Primary hypothyroidism Destruction of thyroid gland Deficient synthesis of TH Impaired secretion of TSH Central (secondary/tertiary) hypothyroidism pituitary or hypothalamic failure with failure to stimulate normal thyroid function (impaired secretion of TRH) Craft AJ, Gordon C, Tiziani A. Understanding pathophysiology. 1st ed. Chatswood, Mosby; 2011  Hypothyroidism Pathophysiology Many potential causes of acquired deficiency of thyroid hormone Most common cause: autoimmune thyroiditis (Hashimoto’s disease/thyroiditis) Autoimmune disease Attack gland or block TSH receptor without activating it Total destruction of the gland 5-10x more common in women iodine deficiency (rare nowadays due to iodized salts) surgical removal of gland (thyroidectomy) radiation therapy (complications of hyperthyroidism treatment) medications genetic defects Strayer D, Rubin E. Rubin's Pathology: Clinicopathologic Foundations of Medicine. 7th ed. UK, Wolters Kluwer/Lippincott Williams & Wilkins; 2014  Hypothyroidism Clinical Manifestations May affect almost all body functions Gradual manifestations Manifestations are related to two main factors: Hypometabolic state resulting from thyroid hormone deficit Fatigue, weakness, lethargy Cold intolerance Constipation Dry skin, course hair Impaired reproduction Impaired memory Craft AJ, Gordon C, Tiziani A. Understanding pathophysiology. 1st ed. Chatswood, Mosby;2011 Myxedematous involvement of body tissues Myxedema: protein–carbohydrate complexes accumulate in the extracellular matrix drawing water into the tissues boggy, nonpitting, edematous soft tissues face and mucous membranes, hands, feet Goiter may also be present Gland enlarge in order to increase function Kumar, Robbins & Cotran: Pathophysiological basis of disease. 8th ed. Philadelphia: Saunders;2010  Hypothyroidism Diagnostic Criteria History and physical examination Laboratory studies Elevated TSH level in primary Low Free T4 in primary Thyroid uptake (radioactive iodine uptake test) to test gland function Thyroid autoantibodies for Hashimoto disease (and Graves disease) Antithyroglobulin for Hashimoto disease  Hypothyroidism Treatment Lifelong thyroid hormone replacement therapy Synthetic form of T4: levothyroxine Goal is to normalize T3, T4 and TSH levels When serum TSH level normalized, T4 level is considered satisfactory Alleviate clinical signs and symptoms Clinical manifestations of altered thyroid hormone Porth C. Pathophysiology : concepts of altered health states. 7th ed. Philadelphia, Lippincott Williams & Wilkins; 2005. McCance KL, Huether S. Pathophysiology. 7th ed. N.S.W, Mosby; 2015