Quality Control and Interpretation of Laboratory Tests of Thyroid Hormones for Nursing and Midwifery Dr. M. Navidhamidi Tehran University of Medical Sciences ١
Physiopathology of Thyroid Gland ٢
Thyroid Gland ٣
۴ Harrison s Principles of Internal Medicine, 17th Edition, 2010
Thyroid Histology ۵
Thyroid Histology Colloid consists of Thyroglobulin ۶
Thyroid Histology The second group of thyroid secretory cells is the C cells or parafollicular cells, which contain and secrete the hormone calcitonin. Calcitonin acts to reduce blood calcium (Ca 2+ ), opposing the effects of parathyroid hormone (PTH). ٧
Thyroid Physiology The average daily iodine requirement is 150 μg/d, which can be derived from foods such as fish, milk, and eggs or as additives in bread or salt In most developed countries, supplementation of table salt means thatt the average dietary intake is approximately 500 μg/d. ٨
Thyroid Physiology The thyroid is the storage site of >90% of the body s iodine content and accounts for one third of the plasma iodine loss. The remaining plasma iodineiscleared viarenal excretion. ٩
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Organification, Coupling, Storage of Thyroid Hormones Iodide Trapping Organification Coupling ١١
Organification, Coupling,Storage, Release of Thyroid Hormones ١٢
Other Factors That Influence Hormone Synthesis and Release Insulin like growth factor I (IGF I) Epidermal growth factor Transforming growth factor β (TGF β) ١٣
Examples In acromegaly, for example, increased levels of growth hormone and IGF I are associated with goiter and predisposition to multinodular goiter (MNG). ١۴
Transport and Protein Binding ١۵
Effect of variations in the concentrations of thyroid hormone binding proteins in the plasma ١۶
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Nuclear Thyroid Hormone Receptors ١٨
Effect of starvation on plasma levels of T4, T 3, 3 and RT 3 in humans ١٩
Thyroid Disorders ٢٠
HYPOTHYROIDISM Iodine deficiency remains the most common cause of hypothyroidism y worldwide ٢١
Endemic goiter Worldwide, diffuse goiter is most commonly caused by iodine deficiency and is termed endemic goiter when it affects >5% of the population. In iodine deficient areas, thyroid enlargement reflects a compensatory effort to trap iodide and produce sufficient hormone under conditions in which hormone synthesis is relatively inefficient. ٢٢
Endemic goiter Endemic goiter is also caused by exposure environmental goitrogens such as cassava root, which contains Cruciferae family and cauliflower); and milk goitrogens are present in grass. to a thiocyanate; vegetables of the (e.g., brussels sprouts, cabbage, from regions where ٢٣
CONGENITAL HYPOTHYROIDISM (Cretinism) Hypothyroidism occurs in about 1 in 4000 newborns. Causes of congenital hypothyroidism Ganong, 2012 ٢۴
CONGENITAL HYPOTHYROIDISM (Cretinism) Clinical Manifestations: The majority of infants appear normal at birth, and <10% are diagnosed based on clinical features, which include prolonged jaundice, feeding problems, hypotonia, enlarged tongue, delayed bone maturation, and umbilical hernia. Importantly, permanent neurologic damage results if treatment is delayed. ٢۵
CONGENITAL HYPOTHYROIDISM (Cretinism) Because of the severe neurologic consequences of untreated congenital hypothyroidism, neonatal screening programs have been established. These are generally based on measurement of TSH or T4 levelsin heelprick blood specimens. A six week old male presents with ٢۶ lethargy and hypotonia
CONGENITAL HYPOTHYROIDISM (Cretinism) Cretins are dwarfed and mentally retarded. When themotherishypothyroidaswell,asinthecaseof iodine deficiency, the mental deficiency is more severe and less responsive to treatmentt t after birth. It has been estimated that 20 million people in the world now have various degrees of brain damage caused by iodine deficiency in utero. ٢٧
AUTOIMMUNE HYPOTHYROIDISM Autoimmune hypothyroidism may be associated with a goiter (Hashimoto s, or goitrous thyroiditis) or, at the later stages of the disease, minimal residual thyroid tissue (atrophic thyroiditis). The mean annual incidence rate of autoimmune hypothyroidism is up to 4 per 1000 women and 1 per 1000 men. The mean age at diagnosis is 60 years, andtheprevalenceof overt hypothyroidism increases with age. ٢٨
AUTOIMMUNE HYPOTHYROIDISM In atrophic thyroiditis, the fibrosis is much more extensive, lymphocyte infiltration is less pronounced, and thyroid follicles are almost completely absent. ٢٩
Hypothyroidism Signs The skin is dry, and there is decreased sweating, thinning of the epidermis. Increased dermal glycosaminoglycan gy gy content traps water, giving grise to skin thickening without pitting (myxedema). Typical features include a puffy face with edematous eyelids and nonpitting pretibial edema. ٣٠ Myxedema
Hypothyroidism Signs Nail growth is retarded, and hair is dry, brittle, and difficult tomanageand fll falls outeasily. Inaddition i to diffuse alopecia, there is thinning of the outer third of the eyebrows, although this is not a specific sign of hypothyroidism. ٣١
Hypothyroidism Signs Thyroid hormones o are necessary for hepatic conversion o of carotene to vitamin A, and the accumulation of carotene in the bloodstream (carotenemia) in hypothyroidism is responsible for the yellowish tint of the skin. Carotenemia can be distinguished from jaundice because in the former condition the scleras are not yellow. ٣٢
Hypothyroidism Signs The other signs are: constipation, i weight gain (despite a poor appetite), Libido is decreased in both sexes, there may be oligomenorrhea or amenorrhea in longstanding disease, but menorrhagia is also common. ٣٣
Hypothyroidism Signs Myocardial contractility and pulse rate are reduced, leading to a reduced stroke volume and bradycardia. Increased peripheral resistance may be accompanied by hypertension, particularly diastolic. Blood flow is diverted from the skin, producing cool extremities. ٣۴
Hyperthyroidismh ٣۵
Hyperthyroidism (Thyrotoxicosis) Graves disease Toxic Multi Nodular Guiter(MNG) Toxic adenomas ٣۶
Diffuse Toxic Goiter(Graves Disease) Graves disease accounts for 60 80% of thyrotoxicosis. High iodine intake is associated with an increased prevalence of Graves disease. Graves disease occurs in up to 2% of women but is one tenth as frequent in men. The disorder rarely begins before adolescence and typically y occurs between 20 and 50 years of age, but it also occurs in the elderly. ٣٧
Diffuse Toxic Goiter(Graves Disease) Stress is an important environmental factor, presumably operating through neuroendocrine effects on the immune system. Smoking is a minor risk factor for Graves disease and a major risk factor for the development of ophthalmopathy. p Another hallmark of Graves disease is the occurrence of swelling of tissues in the orbits, producing protrusion of the eyeballs (exophthalmos). ٣٨
Diffuse Toxic Goiter(Graves Disease) Sudden increases in iodine intake may precipitate Graves disease, and there is a threefold increase in the occurrence of Graves disease in the postpartum period. The hyperthyroidism of Graves disease is caused by TSIs that are synthesized in the thyroid gland as well as in bone marrow and lymph nodes. ٣٩
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Toxic Multinodular Goiter The patient is usually elderly and may present with atrial fibrillation or palpitations, p tachycardia, nervousness, tremor, or weight loss. Recent exposure to iodine, from contrast dyes or other sources, may precipitate or exacerbate thyrotoxicosis. ۴١
DIFFUSE NONTOXIC (SIMPLE) GOITER When diffuse enlargement of the thyroid occurs in the absence of nodules and hyperthyroidism, it is referred to as a diffuse nontoxic goiter. This is sometimes called simple goiter, because of the absence of nodules, or colloid goiter, because of the presence of uniform follicles that are filled with colloid. ۴٢
Hyperthyroidism Signs Hyperthyroidism is characterized by nervousness; weight loss; hyperphagia; p heat intolerance; increased pulse pressure; a fine tremor of the outstretched fingers; warm, soft skin; sweating; and a BMR from +10 to as high as +100. ۴٣
Hyperthyroidism Signs Muscle weakness occurs in most patients with hyperthyroidism (thyrotoxic myopathy), and when the hyperthyroidism is severe and prolonged, the myopathy may be severe. The muscle weakness may be due in part to increased protein catabolism. ۴۴
Thyrotoxic crisis Thyrotoxic crisis, or thyroid storm, is rare and presents as a life threatening exacerbation of hyperthyroidism, y accompanied by fever, delirium, seizures, coma, vomiting, diarrhea, and jaundice. The mortality rate due to cardiac failure, arrhythmia, or hyperthermia is as high as 30%, evenwith treatment. ۴۵
Thyrotoxic crisis Thyrotoxic crisis is usually illness (e.g., stroke, infection, precipitated by acute trauma, diabetic ketoacidosis), surgery (especially on the thyroid), or radioiodine treatment of a patient with partially treated or untreated hyperthyroidism. ۴۶
Thank you for your attention ۴٧