Hypothyroidism causes AND ITS EFFECT Lectures by Dr Alamzeb

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Diagnostic Tests in HypothyroidismMedical education is the process of training and developing future physicians and other health professionals. • Hypothyroidism, causes AND ITS EFFECT • Hypothyroidism, also called underactive thyroid, is when the thyroid gland doesn't make enough thyroid hormones to meet body needs. • Hypothyroidism may not cause noticeable symptoms in its early stages. • Over time, hypothyroidism that isn't treated can lead to other health problems, such as high cholesterol and heart problems. • The effects of hypothyroidism are opposite to those of hyperthyroidism, but there are a few physiological mechanisms peculiar to hypothyroidism. • Hashimoto disease • Hypothyroidism, like hyperthyroidism, is often initiated by autoimmunity against the thyroid gland (Hashimoto disease), but immunity that destroys the gland rather than stimulates it. • The thyroid glands of most of these patients first have autoimmune “thyroiditis,” which means thyroid inflammation. • This causes progressive deterioration and finally fibrosis of the gland, with resultant diminished or absent secretion of thyroid hormone. • Endemic Colloid Goiter Caused by Dietary Iodide Deficiency • The term “goiter” means a greatly enlarged thyroid gland. • 50 milligrams of iodine are required each year for the formation of adequate quantities of thyroid hormone. • In certain areas of the world, insufficient iodine is present in the soil for the foodstuffs to contain even this minute quantity. • Therefore, in the days before iodized table salt, many people who lived in these areas developed extremely large thyroid glands, called endemic goiters. • Mechanism for development of large endemic goiters • Lack of iodine prevents production of both thyroxine and triiodothyronine. • This causes the pituitary to secrete excessively large quantities of TSH. • The TSH then stimulates the thyroid cells to secrete tremendous amounts of thyroglobulin colloid into the follicles, and the gland grows larger and larger. • But because of lack of iodine, thyroxine and triiodothyronine production does not occur in the thyroglobulin molecule and therefore does not cause the normal suppression of TSH production by the anterior pituitary. • The follicles become tremendous in size, and the thyroid gland may increase to 10 to 20 times’ normal size. • Abnormality of the enzyme system required for formation of the thyroid hormones • Occur in people who do not have iodine deficiency. • These goitrous glands may secrete normal quantities of thyroid hormones, but more frequently, the secretion of hormone is depressed, as in endemic colloid goiter. • The exact cause of idiopathic colloid goiter is not known. • Most of these patients show signs of mild thyroiditis; which causes slight hypothyroidism leads to increased TSH secretion and progressive growth of the noninflamed portions of the gland. • This could explain why these glands are usually nodular, with some portions of the gland growing while other portions are being destroyed by thyroiditis. • #Hypothyroidism, causes and its effects on body# • . Deficient iodide-trapping mechanism, in which iodine is not pumped adequately into the thyroid cells • 2. Deficient peroxidase system, in which the iodides are not oxidized to the iodine state • Cretinism • Cretinism is caused by extreme hypothyroidism during fetal life, infancy, or childhood. • This condition is characterized especially by failure of body growth and by mental retardation. • It results from congenital lack of a thyroid gland (congenital cretinism), from failure of the thyroid gland to produce thyroid hormone because of a genetic defect of the gland, or from iodine lack in the diet (endemic cretinism). • The severity of endemic cretinism varies greatly, depending on the amount of iodine in the diet, and whole populaces of an endemic geographic iodine-deficient soil area have been known to have cretinoid tendencies. • The symptoms of cretinism include lack of weight gain, stunted growth, • lethargy, poor feeding, fatigue, thickened facial features, abnormal bone growth, mental retardation, very little crying, constipation, floppiness, excessive sleep, low muscle tones, hoarse voice, unusually large tongue, swelling near the navel, and neck • The free thyroxine in the blood is low. • Treatment of Hypothyroidism • It is easy to maintain a steady level of thyroid hormone activity in the body by daily oral ingestion of a tablet or more containing thyroxine. • The basal metabolic rate in myxedema ranges between −30 and −50. • The secretion of TSH usually greatly increased (except in those rare instances of hypothyroidism caused by depressed response of the pituitary gland to TRH).

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