12 甲状腺功能亢进症与甲状腺功能减退症3

nullThyroid pathophysiologyThyroid pathophysiologyGuo QinglianNew words and exprssionsNew words and exprssionsThyroxine (T4) 　甲状腺素 Triiodothyronine (T3)　三碘甲腺原氨酸 Pathophysiology　病理 Iodination　碘化 Tyrosine　酪氨酸 Thyroglobulin　甲状腺球蛋白 Congenital　先天的 Skeletal 　骨骼 Albumin　白蛋白 Prealbumin　前白蛋白 Titre (titer)　效价 Goitre (goiter)　甲状腺肿 Euthyroid 　甲状腺功能正常的IntroductionIntroduction Thyroid hormones are synthesized in the thyroid gland, including: thyroxine (T4) triiodothyronine (T3) nullnullThe thyroid gland secretes mostly T4 (100nmol/L in plasma) and nearly 20% T3. The peripheral tissues (liver, kidney) deiodinate T4 to produce approximately two-thirds of the circulating T3 (around 2nmol/L). T3 has biologically activity. T3 can bind to receptors and triggers the end-organ effects of the thyroid hormones. In pathophysiologic situations, the quantity of reverse T3 (rT3) will increase.Thyroid hormone actionThyroid hormone action Thyroid hormones are essential for the normal maturation and metabolism of all the tissues in the body. So, insufficient thyroid hormones can result some abnormal situations: permanent brain damage (congenital hypothyroidism) delayed skeletal maturation short stature delayed puberty (青春期)Thyroid hormone actionThyroid hormone actionThyroid hormone effects on metabolism are diverse. For protein synthesis: normal concentration improve high concentration suppress For carbohydrate synthesis: improve liver-glycogen(糖原) decomposion inprove the metabolism of carbohydrate For lipid metabolism: improve the synthesis of cholesterol improve the metabolizing of cholesterolBinding in plasmaBinding in plasmaIn plasma, over 99.95% of T4 is transported bound to protein. 70% carried by thyroxine binding globulin(TBG) 25% by albumin 5% by prealbumin In plasma, over 99.5% of T3 is transported by the same protein. The free T3 or T4 are important for the biological effects of the hormones.Regulation of thyroid hormone secretionRegulation of thyroid hormone secretionOutline of the hypothalamic-pituitary-thyroid axisRegulation of thyroid hormone secretionRegulation of thyroid hormone secretion Conclusion If a patient’s thyroid is producing too much thyroid hormone, then the circulating TSH will be suppressed. If the thyroid is not secreting enough thyroid hormone, the TSH levels will be very high in an attempt to stimulate the gland to secrete more.Thyroid function testsThyroid function tests Thyroid function test means biochemical measurements in the diagnosis of thyroid disease. Testing items: T4 status (total T4 and free T4) T3 status (total T3 and free T3) TSH level TRH test: intravenous injection of TRH and the measurement of pituitary TSH secreted in response to the stimulation. The titer of autoantibodies to thyroid tissue antigensnullThyroid function testsThyroid function tests The TRH test is used in two ways: Investigation of pituitary disorders. There will be a subnormal TSH response if the pituitary can’t make TSH. Investigation of hyperthyroidism. Goitre Goitre A goitre is an enlarged thyroid gland.Goitre Goitre The causes of goitre: Hypothyroid Hyperthyroid Euthyroid (甲状腺功能正常的)Thyroid pathophysiology (summary)Thyroid pathophysiology (summary)The thyroid gland synthesizes, stores, and secretes the thyroid hormones T4 and T3 which are important for normal development and metabolism. The secretion of thyroid hormones is controlled primarily by TSH from the anterior pituitary. Most T4 and T3 circulates in plasma bound to protein. Only a small proportion is not bound, yet it is this ‘free’ fraction which is biologically important.Thyroid pathophysiology (summary)Thyroid pathophysiology (summary)Knowledge of TSH, thyroid hormone and binding protein concentrations in serum may all be needed in the assessment of a patient’s thyroid status. A patient may have severe thyroid disease, such as a large goitre or thyroid cancer, yet have normal concentrations of thyroid hormones in blood.null