Ultrasonography Thyroid ultrasonography may be helpful in determining the cause of hypothyroidism by providing important information on location, size, structure, and vascularity of the gland. In autoimmune thyroiditis a gross inhomogeneity and low echogenicity characterize the echo pattern of the gland. Areas of apparently normal tissue of variable size may be observed, whereas true nodules reflect a different aetiology and should raise the possibility of coexisting nodular goitre, adenomas, or malignancies. A diffuse low thyroid echogenicity is indicative of diffuse autoimmune involvement of the gland and is associated with or may predict the development of hypothyroidism. Studies using colour flow Doppler show a variable degree of vascularity in goitrous autoimmune thyroiditis, whereas vascularity is decreased in the atrophic variant of the dis ease. In subacute thyroiditis the gland is usually enlarged and presents large hypoechoic areas with poorly defined boundaries, mainly within the painful lobe. A large diffuse or multinodular goitre can be documented by ultrasonography in hypothyroidism with inherited defects in thyroid hormone biosynthesis. No evidence of thyroidal tissue in its appropriate location and the demonstration of an ectopic gland are helpful in the diagnosis of congenital hypothyroidism due to thyroid dysgenesis.

In Vivo Isotopic Tests

Thyroid scintiscan may be helpful in the evaluation of hypothyroid patients to indicate the location of functioning thyroid tissue and to provide an estimation of overall thyroid size, although in this regard better evidence is usually obtained by thyroid ultrasonography. Occasionally scintiscan may reveal ectopic thyroid tissue not discernible by other means (e.g. lingual thyroid). Thyroid scintiscan can also be used to reveal substernal thyroid tissue when hypothyroidism is associated with a large goitre.

Radioiodine uptake is expressed as the percentage of radio activity that is trapped by the thyroid at a given time after administration of a tracer quantity of inorganic radioiodine. Early radioiodine uptake measurements (3– 6 h) provide information on the rates of transport and organification of iodide within the gland, whereas 24- and 48- h radioiodine uptake measurement reflects the rate of release of radioiodine from thyroidal tissue. It is also a way of estimating the extrathyroidal pool of iodide, being low to absent after intake of excess iodide but increased in iodine deficiency. An exception is represented by amiodarone- induced hypothyroidism in which radioiodine uptake is preserved despite iodine excess. Radioiodine uptake is increased if hypothyroidism is caused by defective synthesis of thyroid hormones since TSH stimulates all steps in hormone synthesis capable of response. In chronic autoimmune thyroiditis values of the radioiodine up take depend on the amount of residual functioning thyroid tissue and the serum concentration of TSH. Radioiodine uptake may be normal or even increased during the initial phase of chronic thyroiditis, whereas it tends to decrease as the disease progresses. Very low values of the radioiodine uptake are characteristic of the early phase of destructive thyroiditis (e.g. subacute thyroiditis) which is usually associated with thyrotoxicosis caused by follicular disruption. In these cases, return of radioiodine uptake to within the normal range may be helpful to indicate recovery of thyroid function. Radioiodine uptake measurement, which is obviously reduced in postablative hypothyroidism, may be used occasionally to estimate the amount of residual thyroid tissue after thyroidectomy or radioactive treatment.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم بين الحرمين ينفّذ أعمال غسل الساحة الوسطية والطرق المؤدية إليها

جمعية العميد تصدر كتابًا علميًّا عن الكليَّات القرآنيَّة

لإحياء التراث الإسلامي.. قسم شؤون المعارف يقيم دوراتٍ وندواتٍ تخصصية في تحقيق المخطوطات

قسم الحزام الأخضر يباشر زراعة نحو 2000 شتلة في واحاته

المزيد

الآخبار الصحية

ما هي أفضل العصائر لصحة القلب وتقوية المناعة والنوم العميق؟

الأطعمة الغنية بالبروتينات النباتية تقلل خطر الأمراض المزمنة

وجع الأوتار قد يخفي خطرا صحيا مرتبطا بالقلب

أزمة "السفينة الموبوءة"..الأرجنتين تحقق في مصدر تفشي "هانتا"

المزيد

الآخبار التكنلوجية

باحثون يحددون تأثير القهوة على الميكروبيوم والمزاج

روسيا.. ابتكار تقنية لمعالجة سبائك التيتانيوم لحماية الطائرات والسيارات

بكين وواشنطن تدرسان إطلاق محادثات رسمية حول الذكاء الاصطناعي

لأول مرة في الولايات المتحدة.. تشغيل مفاعل مصغر نووي يغذي الذكاء الاصطناعي بالطاقة

المزيد

مواضيع ذات صلة

Assisted Reproductive Technology

Cultivation of Microorganisms : Sources of Metabolic Energy

Cultivation of Microorganisms : Requirements for Growth

Renewal of Epithelial Cells

Transport Across Epithelia

Covering or Lining Epithelia

Anticoagulants for Clinical use

The Rationale and Methodology for Hepcidin-Lowering Agents

Therapy of Iron Deficiency

Intestinal Iron Absorption

Liver Regulation of Systemic Iron Homeostasis and Iron Storage

Recycling of Erythrocyte Iron by Macrophages